variable

package
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 Go to latest Published: Dec 24, 2024 License: Apache-2.0 Imports: 85 Imported by: 0

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Constants

View Source 
const (
	// PlacementModeStrict indicates all placement operations should be checked strictly in ddl
	PlacementModeStrict string = "STRICT"
	// PlacementModeIgnore indicates ignore all placement operations in ddl
	PlacementModeIgnore string = "IGNORE"
)
View Source 
const (
	// ConnTypeSocket indicates socket without TLS.
	ConnTypeSocket string = "TCP"
	// ConnTypeUnixSocket indicates Unix Socket.
	ConnTypeUnixSocket string = "UnixSocket"
	// ConnTypeTLS indicates socket with TLS.
	ConnTypeTLS string = "SSL/TLS"
)
View Source 
const (
	// SlowLogRowPrefixStr is slow log row prefix.
	SlowLogRowPrefixStr = "# "
	// SlowLogSpaceMarkStr is slow log space mark.
	SlowLogSpaceMarkStr = ": "
	// SlowLogSQLSuffixStr is slow log suffix.
	SlowLogSQLSuffixStr = ";"
	// SlowLogTimeStr is slow log field name.
	SlowLogTimeStr = "Time"
	// SlowLogStartPrefixStr is slow log start row prefix.
	SlowLogStartPrefixStr = SlowLogRowPrefixStr + SlowLogTimeStr + SlowLogSpaceMarkStr
	// SlowLogTxnStartTSStr is slow log field name.
	SlowLogTxnStartTSStr = "Txn_start_ts"
	// SlowLogKeyspaceName is slow log field name.
	SlowLogKeyspaceName = "Keyspace_name"
	// SlowLogKeyspaceID is slow log field name.
	SlowLogKeyspaceID = "Keyspace_ID"
	// SlowLogUserAndHostStr is the user and host field name, which is compatible with MySQL.
	SlowLogUserAndHostStr = "User@Host"
	// SlowLogUserStr is slow log field name.
	SlowLogUserStr = "User"
	// SlowLogHostStr only for slow_query table usage.
	SlowLogHostStr = "Host"
	// SlowLogConnIDStr is slow log field name.
	SlowLogConnIDStr = "Conn_ID"
	// SlowLogSessAliasStr is the session alias set by user
	SlowLogSessAliasStr = "Session_alias"
	// SlowLogQueryTimeStr is slow log field name.
	SlowLogQueryTimeStr = "Query_time"
	// SlowLogParseTimeStr is the parse sql time.
	SlowLogParseTimeStr = "Parse_time"
	// SlowLogCompileTimeStr is the compile plan time.
	SlowLogCompileTimeStr = "Compile_time"
	// SlowLogRewriteTimeStr is the rewrite time.
	SlowLogRewriteTimeStr = "Rewrite_time"
	// SlowLogOptimizeTimeStr is the optimization time.
	SlowLogOptimizeTimeStr = "Optimize_time"
	// SlowLogWaitTSTimeStr is the time of waiting TS.
	SlowLogWaitTSTimeStr = "Wait_TS"
	// SlowLogPreprocSubQueriesStr is the number of pre-processed sub-queries.
	SlowLogPreprocSubQueriesStr = "Preproc_subqueries"
	// SlowLogPreProcSubQueryTimeStr is the total time of pre-processing sub-queries.
	SlowLogPreProcSubQueryTimeStr = "Preproc_subqueries_time"
	// SlowLogDBStr is slow log field name.
	SlowLogDBStr = "DB"
	// SlowLogIsInternalStr is slow log field name.
	SlowLogIsInternalStr = "Is_internal"
	// SlowLogIndexNamesStr is slow log field name.
	SlowLogIndexNamesStr = "Index_names"
	// SlowLogDigestStr is slow log field name.
	SlowLogDigestStr = "Digest"
	// SlowLogQuerySQLStr is slow log field name.
	SlowLogQuerySQLStr = "Query" // use for slow log table, slow log will not print this field name but print sql directly.
	// SlowLogStatsInfoStr is plan stats info.
	SlowLogStatsInfoStr = "Stats"
	// SlowLogNumCopTasksStr is the number of cop-tasks.
	SlowLogNumCopTasksStr = "Num_cop_tasks"
	// SlowLogCopProcAvg is the average process time of all cop-tasks.
	SlowLogCopProcAvg = "Cop_proc_avg"
	// SlowLogCopProcP90 is the p90 process time of all cop-tasks.
	SlowLogCopProcP90 = "Cop_proc_p90"
	// SlowLogCopProcMax is the max process time of all cop-tasks.
	SlowLogCopProcMax = "Cop_proc_max"
	// SlowLogCopProcAddr is the address of TiKV where the cop-task which cost max process time run.
	SlowLogCopProcAddr = "Cop_proc_addr"
	// SlowLogCopWaitAvg is the average wait time of all cop-tasks.
	SlowLogCopWaitAvg = "Cop_wait_avg" // #nosec G101
	// SlowLogCopWaitP90 is the p90 wait time of all cop-tasks.
	SlowLogCopWaitP90 = "Cop_wait_p90" // #nosec G101
	// SlowLogCopWaitMax is the max wait time of all cop-tasks.
	SlowLogCopWaitMax = "Cop_wait_max"
	// SlowLogCopWaitAddr is the address of TiKV where the cop-task which cost wait process time run.
	SlowLogCopWaitAddr = "Cop_wait_addr" // #nosec G101
	// SlowLogCopBackoffPrefix contains backoff information.
	SlowLogCopBackoffPrefix = "Cop_backoff_"
	// SlowLogMemMax is the max number bytes of memory used in this statement.
	SlowLogMemMax = "Mem_max"
	// SlowLogDiskMax is the max number bytes of disk used in this statement.
	SlowLogDiskMax = "Disk_max"
	// SlowLogPrepared is used to indicate whether this sql execute in prepare.
	SlowLogPrepared = "Prepared"
	// SlowLogPlanFromCache is used to indicate whether this plan is from plan cache.
	SlowLogPlanFromCache = "Plan_from_cache"
	// SlowLogPlanFromBinding is used to indicate whether this plan is matched with the hints in the binding.
	SlowLogPlanFromBinding = "Plan_from_binding"
	// SlowLogHasMoreResults is used to indicate whether this sql has more following results.
	SlowLogHasMoreResults = "Has_more_results"
	// SlowLogSucc is used to indicate whether this sql execute successfully.
	SlowLogSucc = "Succ"
	// SlowLogPrevStmt is used to show the previous executed statement.
	SlowLogPrevStmt = "Prev_stmt"
	// SlowLogPlan is used to record the query plan.
	SlowLogPlan = "Plan"
	// SlowLogPlanDigest is used to record the query plan digest.
	SlowLogPlanDigest = "Plan_digest"
	// SlowLogBinaryPlan is used to record the binary plan.
	SlowLogBinaryPlan = "Binary_plan"
	// SlowLogPlanPrefix is the prefix of the plan value.
	SlowLogPlanPrefix = ast.TiDBDecodePlan + "('"
	// SlowLogBinaryPlanPrefix is the prefix of the binary plan value.
	SlowLogBinaryPlanPrefix = ast.TiDBDecodeBinaryPlan + "('"
	// SlowLogPlanSuffix is the suffix of the plan value.
	SlowLogPlanSuffix = "')"
	// SlowLogPrevStmtPrefix is the prefix of Prev_stmt in slow log file.
	SlowLogPrevStmtPrefix = SlowLogPrevStmt + SlowLogSpaceMarkStr
	// SlowLogKVTotal is the total time waiting for kv.
	SlowLogKVTotal = "KV_total"
	// SlowLogPDTotal is the total time waiting for pd.
	SlowLogPDTotal = "PD_total"
	// SlowLogBackoffTotal is the total time doing backoff.
	SlowLogBackoffTotal = "Backoff_total"
	// SlowLogWriteSQLRespTotal is the total time used to write response to client.
	SlowLogWriteSQLRespTotal = "Write_sql_response_total"
	// SlowLogExecRetryCount is the execution retry count.
	SlowLogExecRetryCount = "Exec_retry_count"
	// SlowLogExecRetryTime is the execution retry time.
	SlowLogExecRetryTime = "Exec_retry_time"
	// SlowLogBackoffDetail is the detail of backoff.
	SlowLogBackoffDetail = "Backoff_Detail"
	// SlowLogResultRows is the row count of the SQL result.
	SlowLogResultRows = "Result_rows"
	// SlowLogWarnings is the warnings generated during executing the statement.
	// Note that some extra warnings would also be printed through slow log.
	SlowLogWarnings = "Warnings"
	// SlowLogIsExplicitTxn is used to indicate whether this sql execute in explicit transaction or not.
	SlowLogIsExplicitTxn = "IsExplicitTxn"
	// SlowLogIsWriteCacheTable is used to indicate whether writing to the cache table need to wait for the read lock to expire.
	SlowLogIsWriteCacheTable = "IsWriteCacheTable"
	// SlowLogIsSyncStatsFailed is used to indicate whether any failure happen during sync stats
	SlowLogIsSyncStatsFailed = "IsSyncStatsFailed"
	// SlowLogResourceGroup is the resource group name that the current session bind.
	SlowLogResourceGroup = "Resource_group"
	// SlowLogRRU is the read request_unit(RU) cost
	SlowLogRRU = "Request_unit_read"
	// SlowLogWRU is the write request_unit(RU) cost
	SlowLogWRU = "Request_unit_write"
	// SlowLogWaitRUDuration is the total duration for kv requests to wait available request-units.
	SlowLogWaitRUDuration = "Time_queued_by_rc"
	// SlowLogTidbCPUUsageDuration is the total tidb cpu usages.
	SlowLogTidbCPUUsageDuration = "Tidb_cpu_time"
	// SlowLogTikvCPUUsageDuration is the total tikv cpu usages.
	SlowLogTikvCPUUsageDuration = "Tikv_cpu_time"
)
View Source 
const (
	// OptObjectiveModerate is a possible value and the default value for TiDBOptObjective.
	// Please see comments of SessionVars.OptObjective for details.
	OptObjectiveModerate string = "moderate"
	// OptObjectiveDeterminate is a possible value for TiDBOptObjective.
	OptObjectiveDeterminate = "determinate"
)
View Source 
const (
	ForcePreAggStr    = "force_preagg"
	AutoStr           = "auto"
	ForceStreamingStr = "force_streaming"
)

ForcePreAggStr means 1st hashagg will be pre aggregated. AutoStr means TiFlash will decide which policy for 1st hashagg. ForceStreamingStr means 1st hashagg will for pass through all blocks.

View Source 
const (
	// ScatterOff means default, will not scatter region
	ScatterOff string = ""
	// ScatterTable means scatter region at table level
	ScatterTable string = "table"
	// ScatterGlobal means scatter region at global level
	ScatterGlobal string = "global"
)
View Source 
const (
	// MaskPwd is the mask of password for LDAP variables.
	MaskPwd = "******"

	// PessimisticTxnMode is the name for tidb_txn_mode system variable.
	PessimisticTxnMode = "pessimistic"
	// OptimisticTxnMode is the name for tidb_txn_mode system variable.
	OptimisticTxnMode = "optimistic"
)
View Source 
const (
	// CharacterSetConnection is the name for character_set_connection system variable.
	CharacterSetConnection = "character_set_connection"
	// CollationConnection is the name for collation_connection system variable.
	CollationConnection = "collation_connection"
	// CharsetDatabase is the name for character_set_database system variable.
	CharsetDatabase = "character_set_database"
	// CollationDatabase is the name for collation_database system variable.
	CollationDatabase = "collation_database"
	// CharacterSetFilesystem is the name for character_set_filesystem system variable.
	CharacterSetFilesystem = "character_set_filesystem"
	// CharacterSetClient is the name for character_set_client system variable.
	CharacterSetClient = "character_set_client"
	// CharacterSetSystem is the name for character_set_system system variable.
	CharacterSetSystem = "character_set_system"
	// GeneralLog is the name for 'general_log' system variable.
	GeneralLog = "general_log"
	// AvoidTemporalUpgrade is the name for 'avoid_temporal_upgrade' system variable.
	AvoidTemporalUpgrade = "avoid_temporal_upgrade"
	// MaxPreparedStmtCount is the name for 'max_prepared_stmt_count' system variable.
	MaxPreparedStmtCount = "max_prepared_stmt_count"
	// BigTables is the name for 'big_tables' system variable.
	BigTables = "big_tables"
	// CheckProxyUsers is the name for 'check_proxy_users' system variable.
	CheckProxyUsers = "check_proxy_users"
	// CoreFile is the name for 'core_file' system variable.
	CoreFile = "core_file"
	// DefaultWeekFormat is the name for 'default_week_format' system variable.
	DefaultWeekFormat = "default_week_format"
	// GroupConcatMaxLen is the name for 'group_concat_max_len' system variable.
	GroupConcatMaxLen = "group_concat_max_len"
	// DelayKeyWrite is the name for 'delay_key_write' system variable.
	DelayKeyWrite = "delay_key_write"
	// EndMarkersInJSON is the name for 'end_markers_in_json' system variable.
	EndMarkersInJSON = "end_markers_in_json"
	// Hostname is the name for 'hostname' system variable.
	Hostname = "hostname"
	// InnodbCommitConcurrency is the name for 'innodb_commit_concurrency' system variable.
	InnodbCommitConcurrency = "innodb_commit_concurrency"
	// InnodbFastShutdown is the name for 'innodb_fast_shutdown' system variable.
	InnodbFastShutdown = "innodb_fast_shutdown"
	// InnodbLockWaitTimeout is the name for 'innodb_lock_wait_timeout' system variable.
	InnodbLockWaitTimeout = "innodb_lock_wait_timeout"
	// MaxSortLength is the name for 'max_sort_length' system variable.
	MaxSortLength = "max_sort_length"
	// MaxSpRecursionDepth is the name for 'max_sp_recursion_depth' system variable.
	MaxSpRecursionDepth = "max_sp_recursion_depth"
	// MaxUserConnections is the name for 'max_user_connections' system variable.
	MaxUserConnections = "max_user_connections"
	// OfflineMode is the name for 'offline_mode' system variable.
	OfflineMode = "offline_mode"
	// InteractiveTimeout is the name for 'interactive_timeout' system variable.
	InteractiveTimeout = "interactive_timeout"
	// FlushTime is the name for 'flush_time' system variable.
	FlushTime = "flush_time"
	// PseudoSlaveMode is the name for 'pseudo_slave_mode' system variable.
	PseudoSlaveMode = "pseudo_slave_mode"
	// LowPriorityUpdates is the name for 'low_priority_updates' system variable.
	LowPriorityUpdates = "low_priority_updates"
	// LowerCaseTableNames is the name for 'lower_case_table_names' system variable.
	LowerCaseTableNames = "lower_case_table_names"
	// SessionTrackGtids is the name for 'session_track_gtids' system variable.
	SessionTrackGtids = "session_track_gtids"
	// OldPasswords is the name for 'old_passwords' system variable.
	OldPasswords = "old_passwords"
	// MaxConnections is the name for 'max_connections' system variable.
	MaxConnections = "max_connections"
	// SkipNameResolve is the name for 'skip_name_resolve' system variable.
	SkipNameResolve = "skip_name_resolve"
	// ForeignKeyChecks is the name for 'foreign_key_checks' system variable.
	ForeignKeyChecks = "foreign_key_checks"
	// SQLSafeUpdates is the name for 'sql_safe_updates' system variable.
	SQLSafeUpdates = "sql_safe_updates"
	// WarningCount is the name for 'warning_count' system variable.
	WarningCount = "warning_count"
	// ErrorCount is the name for 'error_count' system variable.
	ErrorCount = "error_count"
	// DefaultPasswordLifetime is the name for 'default_password_lifetime' system variable.
	DefaultPasswordLifetime = "default_password_lifetime"
	// DisconnectOnExpiredPassword is the name for 'disconnect_on_expired_password' system variable.
	DisconnectOnExpiredPassword = "disconnect_on_expired_password"
	// SQLSelectLimit is the name for 'sql_select_limit' system variable.
	SQLSelectLimit = "sql_select_limit"
	// MaxConnectErrors is the name for 'max_connect_errors' system variable.
	MaxConnectErrors = "max_connect_errors"
	// TableDefinitionCache is the name for 'table_definition_cache' system variable.
	TableDefinitionCache = "table_definition_cache"
	// Timestamp is the name for 'timestamp' system variable.
	Timestamp = "timestamp"
	// ConnectTimeout is the name for 'connect_timeout' system variable.
	ConnectTimeout = "connect_timeout"
	// SyncBinlog is the name for 'sync_binlog' system variable.
	SyncBinlog = "sync_binlog"
	// BlockEncryptionMode is the name for 'block_encryption_mode' system variable.
	BlockEncryptionMode = "block_encryption_mode"
	// WaitTimeout is the name for 'wait_timeout' system variable.
	WaitTimeout = "wait_timeout"
	// Version is the name of 'version' system variable.
	Version = "version"
	// VersionComment is the name of 'version_comment' system variable.
	VersionComment = "version_comment"
	// PluginDir is the name of 'plugin_dir' system variable.
	PluginDir = "plugin_dir"
	// PluginLoad is the name of 'plugin_load' system variable.
	PluginLoad = "plugin_load"
	// TiDBEnableDDL indicates whether the tidb-server campaigns the DDL owner,
	TiDBEnableDDL = "tidb_enable_ddl"
	// TiDBEnableStatsOwner indicates whether the tidb-server campaigns the Stats owner,
	TiDBEnableStatsOwner = "tidb_enable_stats_owner"
	// Port is the name for 'port' system variable.
	Port = "port"
	// DataDir is the name for 'datadir' system variable.
	DataDir = "datadir"
	// Profiling is the name for 'Profiling' system variable.
	Profiling = "profiling"
	// Socket is the name for 'socket' system variable.
	Socket = "socket"
	// BinlogOrderCommits is the name for 'binlog_order_commits' system variable.
	BinlogOrderCommits = "binlog_order_commits"
	// MasterVerifyChecksum is the name for 'master_verify_checksum' system variable.
	MasterVerifyChecksum = "master_verify_checksum"
	// SuperReadOnly is the name for 'super_read_only' system variable.
	SuperReadOnly = "super_read_only"
	// SQLNotes is the name for 'sql_notes' system variable.
	SQLNotes = "sql_notes"
	// QueryCacheType is the name for 'query_cache_type' system variable.
	QueryCacheType = "query_cache_type"
	// SlaveCompressedProtocol is the name for 'slave_compressed_protocol' system variable.
	SlaveCompressedProtocol = "slave_compressed_protocol"
	// BinlogRowQueryLogEvents is the name for 'binlog_rows_query_log_events' system variable.
	BinlogRowQueryLogEvents = "binlog_rows_query_log_events"
	// LogSlowSlaveStatements is the name for 'log_slow_slave_statements' system variable.
	LogSlowSlaveStatements = "log_slow_slave_statements"
	// LogSlowAdminStatements is the name for 'log_slow_admin_statements' system variable.
	LogSlowAdminStatements = "log_slow_admin_statements"
	// LogQueriesNotUsingIndexes is the name for 'log_queries_not_using_indexes' system variable.
	LogQueriesNotUsingIndexes = "log_queries_not_using_indexes"
	// QueryCacheWlockInvalidate is the name for 'query_cache_wlock_invalidate' system variable.
	QueryCacheWlockInvalidate = "query_cache_wlock_invalidate"
	// SQLAutoIsNull is the name for 'sql_auto_is_null' system variable.
	SQLAutoIsNull = "sql_auto_is_null"
	// RelayLogPurge is the name for 'relay_log_purge' system variable.
	RelayLogPurge = "relay_log_purge"
	// AutomaticSpPrivileges is the name for 'automatic_sp_privileges' system variable.
	AutomaticSpPrivileges = "automatic_sp_privileges"
	// SQLQuoteShowCreate is the name for 'sql_quote_show_create' system variable.
	SQLQuoteShowCreate = "sql_quote_show_create"
	// SlowQueryLog is the name for 'slow_query_log' system variable.
	SlowQueryLog = "slow_query_log"
	// BinlogDirectNonTransactionalUpdates is the name for 'binlog_direct_non_transactional_updates' system variable.
	BinlogDirectNonTransactionalUpdates = "binlog_direct_non_transactional_updates"
	// SQLBigSelects is the name for 'sql_big_selects' system variable.
	SQLBigSelects = "sql_big_selects"
	// LogBinTrustFunctionCreators is the name for 'log_bin_trust_function_creators' system variable.
	LogBinTrustFunctionCreators = "log_bin_trust_function_creators"
	// OldAlterTable is the name for 'old_alter_table' system variable.
	OldAlterTable = "old_alter_table"
	// EnforceGtidConsistency is the name for 'enforce_gtid_consistency' system variable.
	EnforceGtidConsistency = "enforce_gtid_consistency"
	// SecureAuth is the name for 'secure_auth' system variable.
	SecureAuth = "secure_auth"
	// UniqueChecks is the name for 'unique_checks' system variable.
	UniqueChecks = "unique_checks"
	// SQLWarnings is the name for 'sql_warnings' system variable.
	SQLWarnings = "sql_warnings"
	// AutoCommit is the name for 'autocommit' system variable.
	AutoCommit = "autocommit"
	// KeepFilesOnCreate is the name for 'keep_files_on_create' system variable.
	KeepFilesOnCreate = "keep_files_on_create"
	// ShowOldTemporals is the name for 'show_old_temporals' system variable.
	ShowOldTemporals = "show_old_temporals"
	// LocalInFile is the name for 'local_infile' system variable.
	LocalInFile = "local_infile"
	// PerformanceSchema is the name for 'performance_schema' system variable.
	PerformanceSchema = "performance_schema"
	// Flush is the name for 'flush' system variable.
	Flush = "flush"
	// SlaveAllowBatching is the name for 'slave_allow_batching' system variable.
	SlaveAllowBatching = "slave_allow_batching"
	// MyISAMUseMmap is the name for 'myisam_use_mmap' system variable.
	MyISAMUseMmap = "myisam_use_mmap"
	// InnodbFilePerTable is the name for 'innodb_file_per_table' system variable.
	InnodbFilePerTable = "innodb_file_per_table"
	// InnodbLogCompressedPages is the name for 'innodb_log_compressed_pages' system variable.
	InnodbLogCompressedPages = "innodb_log_compressed_pages"
	// InnodbPrintAllDeadlocks is the name for 'innodb_print_all_deadlocks' system variable.
	InnodbPrintAllDeadlocks = "innodb_print_all_deadlocks"
	// InnodbStrictMode is the name for 'innodb_strict_mode' system variable.
	InnodbStrictMode = "innodb_strict_mode"
	// InnodbCmpPerIndexEnabled is the name for 'innodb_cmp_per_index_enabled' system variable.
	InnodbCmpPerIndexEnabled = "innodb_cmp_per_index_enabled"
	// InnodbBufferPoolDumpAtShutdown is the name for 'innodb_buffer_pool_dump_at_shutdown' system variable.
	InnodbBufferPoolDumpAtShutdown = "innodb_buffer_pool_dump_at_shutdown"
	// InnodbAdaptiveHashIndex is the name for 'innodb_adaptive_hash_index' system variable.
	InnodbAdaptiveHashIndex = "innodb_adaptive_hash_index"
	// InnodbFtEnableStopword is the name for 'innodb_ft_enable_stopword' system variable.
	InnodbFtEnableStopword = "innodb_ft_enable_stopword" // #nosec G101
	// InnodbSupportXA is the name for 'innodb_support_xa' system variable.
	InnodbSupportXA = "innodb_support_xa"
	// InnodbOptimizeFullTextOnly is the name for 'innodb_optimize_fulltext_only' system variable.
	InnodbOptimizeFullTextOnly = "innodb_optimize_fulltext_only"
	// InnodbStatusOutputLocks is the name for 'innodb_status_output_locks' system variable.
	InnodbStatusOutputLocks = "innodb_status_output_locks"
	// InnodbBufferPoolDumpNow is the name for 'innodb_buffer_pool_dump_now' system variable.
	InnodbBufferPoolDumpNow = "innodb_buffer_pool_dump_now"
	// InnodbBufferPoolLoadNow is the name for 'innodb_buffer_pool_load_now' system variable.
	InnodbBufferPoolLoadNow = "innodb_buffer_pool_load_now"
	// InnodbStatsOnMetadata is the name for 'innodb_stats_on_metadata' system variable.
	InnodbStatsOnMetadata = "innodb_stats_on_metadata"
	// InnodbDisableSortFileCache is the name for 'innodb_disable_sort_file_cache' system variable.
	InnodbDisableSortFileCache = "innodb_disable_sort_file_cache"
	// InnodbStatsAutoRecalc is the name for 'innodb_stats_auto_recalc' system variable.
	InnodbStatsAutoRecalc = "innodb_stats_auto_recalc"
	// InnodbBufferPoolLoadAbort is the name for 'innodb_buffer_pool_load_abort' system variable.
	InnodbBufferPoolLoadAbort = "innodb_buffer_pool_load_abort"
	// InnodbStatsPersistent is the name for 'innodb_stats_persistent' system variable.
	InnodbStatsPersistent = "innodb_stats_persistent"
	// InnodbRandomReadAhead is the name for 'innodb_random_read_ahead' system variable.
	InnodbRandomReadAhead = "innodb_random_read_ahead"
	// InnodbAdaptiveFlushing is the name for 'innodb_adaptive_flushing' system variable.
	InnodbAdaptiveFlushing = "innodb_adaptive_flushing"
	// InnodbTableLocks is the name for 'innodb_table_locks' system variable.
	InnodbTableLocks = "innodb_table_locks"
	// InnodbStatusOutput is the name for 'innodb_status_output' system variable.
	InnodbStatusOutput = "innodb_status_output"
	// NetBufferLength is the name for 'net_buffer_length' system variable.
	NetBufferLength = "net_buffer_length"
	// QueryCacheSize is the name of 'query_cache_size' system variable.
	QueryCacheSize = "query_cache_size"
	// TxReadOnly is the name of 'tx_read_only' system variable.
	TxReadOnly = "tx_read_only"
	// TransactionReadOnly is the name of 'transaction_read_only' system variable.
	TransactionReadOnly = "transaction_read_only"
	// CharacterSetServer is the name of 'character_set_server' system variable.
	CharacterSetServer = "character_set_server"
	// AutoIncrementIncrement is the name of 'auto_increment_increment' system variable.
	AutoIncrementIncrement = "auto_increment_increment"
	// AutoIncrementOffset is the name of 'auto_increment_offset' system variable.
	AutoIncrementOffset = "auto_increment_offset"
	// InitConnect is the name of 'init_connect' system variable.
	InitConnect = "init_connect"
	// CollationServer is the name of 'collation_server' variable.
	CollationServer = "collation_server"
	// DefaultCollationForUTF8MB4 is the name of 'default_collation_for_utf8mb4' variable.
	DefaultCollationForUTF8MB4 = "default_collation_for_utf8mb4"
	// NetWriteTimeout is the name of 'net_write_timeout' variable.
	NetWriteTimeout = "net_write_timeout"
	// ThreadPoolSize is the name of 'thread_pool_size' variable.
	ThreadPoolSize = "thread_pool_size"
	// WindowingUseHighPrecision is the name of 'windowing_use_high_precision' system variable.
	WindowingUseHighPrecision = "windowing_use_high_precision"
	// OptimizerSwitch is the name of 'optimizer_switch' system variable.
	OptimizerSwitch = "optimizer_switch"
	// SystemTimeZone is the name of 'system_time_zone' system variable.
	SystemTimeZone = "system_time_zone"
	// CTEMaxRecursionDepth is the name of 'cte_max_recursion_depth' system variable.
	CTEMaxRecursionDepth = "cte_max_recursion_depth"
	// SQLModeVar is the name of the 'sql_mode' system variable.
	SQLModeVar = "sql_mode"
	// CharacterSetResults is the name of the 'character_set_results' system variable.
	CharacterSetResults = "character_set_results"
	// MaxAllowedPacket is the name of the 'max_allowed_packet' system variable.
	MaxAllowedPacket = "max_allowed_packet"
	// TimeZone is the name of the 'time_zone' system variable.
	TimeZone = "time_zone"
	// TxnIsolation is the name of the 'tx_isolation' system variable.
	TxnIsolation = "tx_isolation"
	// TransactionIsolation is the name of the 'transaction_isolation' system variable.
	TransactionIsolation = "transaction_isolation"
	// TxnIsolationOneShot is the name of the 'tx_isolation_one_shot' system variable.
	TxnIsolationOneShot = "tx_isolation_one_shot"
	// MaxExecutionTime is the name of the 'max_execution_time' system variable.
	MaxExecutionTime = "max_execution_time"
	// TiKVClientReadTimeout is the name of the 'tikv_client_read_timeout' system variable.
	TiKVClientReadTimeout = "tikv_client_read_timeout"
	// TiDBLoadBindingTimeout is the name of the 'tidb_load_binding_timeout' system variable.
	TiDBLoadBindingTimeout = "tidb_load_binding_timeout"
	// ReadOnly is the name of the 'read_only' system variable.
	ReadOnly = "read_only"
	// DefaultAuthPlugin is the name of 'default_authentication_plugin' system variable.
	DefaultAuthPlugin = "default_authentication_plugin"
	// LastInsertID is the name of 'last_insert_id' system variable.
	LastInsertID = "last_insert_id"
	// Identity is the name of 'identity' system variable.
	Identity = "identity"
	// TiDBAllowFunctionForExpressionIndex is the name of `TiDBAllowFunctionForExpressionIndex` system variable.
	TiDBAllowFunctionForExpressionIndex = "tidb_allow_function_for_expression_index"
	// RandSeed1 is the name of 'rand_seed1' system variable.
	RandSeed1 = "rand_seed1"
	// RandSeed2 is the name of 'rand_seed2' system variable.
	RandSeed2 = "rand_seed2"
	// SQLRequirePrimaryKey is the name of `sql_require_primary_key` system variable.
	SQLRequirePrimaryKey = "sql_require_primary_key"
	// ValidatePasswordEnable turns on/off the validation of password.
	ValidatePasswordEnable = "validate_password.enable"
	// ValidatePasswordPolicy specifies the password policy enforced by validate_password.
	ValidatePasswordPolicy = "validate_password.policy"
	// ValidatePasswordCheckUserName controls whether validate_password compares passwords to the user name part of
	// the effective user account for the current session
	ValidatePasswordCheckUserName = "validate_password.check_user_name"
	// ValidatePasswordLength specified the minimum number of characters that validate_password requires passwords to have
	ValidatePasswordLength = "validate_password.length"
	// ValidatePasswordMixedCaseCount specified the minimum number of lowercase and uppercase characters that validate_password requires
	ValidatePasswordMixedCaseCount = "validate_password.mixed_case_count"
	// ValidatePasswordNumberCount specified the minimum number of numeric (digit) characters that validate_password requires
	ValidatePasswordNumberCount = "validate_password.number_count"
	// ValidatePasswordSpecialCharCount specified the minimum number of nonalphanumeric characters that validate_password requires
	ValidatePasswordSpecialCharCount = "validate_password.special_char_count"
	// ValidatePasswordDictionary specified the dictionary that validate_password uses for checking passwords. Each word is separated by semicolon (;).
	ValidatePasswordDictionary = "validate_password.dictionary"
)
View Source 
const (
	TiDBDDLSlowOprThreshold = "ddl_slow_threshold"

	// TiDBSnapshot is used for reading history data, the default value is empty string.
	// The value can be a datetime string like '2017-11-11 20:20:20' or a tso string. When this variable is set, the session reads history data of that time.
	TiDBSnapshot = "tidb_snapshot"

	// TiDBOptAggPushDown is used to enable/disable the optimizer rule of aggregation push down.
	TiDBOptAggPushDown = "tidb_opt_agg_push_down"

	// TiDBOptDeriveTopN is used to enable/disable the optimizer rule of deriving topN.
	TiDBOptDeriveTopN = "tidb_opt_derive_topn"

	// TiDBOptCartesianBCJ is used to disable/enable broadcast cartesian join in MPP mode
	TiDBOptCartesianBCJ = "tidb_opt_broadcast_cartesian_join"

	TiDBOptMPPOuterJoinFixedBuildSide = "tidb_opt_mpp_outer_join_fixed_build_side"

	// TiDBOptDistinctAggPushDown is used to decide whether agg with distinct should be pushed to tikv/tiflash.
	TiDBOptDistinctAggPushDown = "tidb_opt_distinct_agg_push_down"

	// TiDBOptSkewDistinctAgg is used to indicate the distinct agg has data skew
	TiDBOptSkewDistinctAgg = "tidb_opt_skew_distinct_agg"

	// TiDBOpt3StageDistinctAgg is used to indicate whether to plan and execute the distinct agg in 3 stages
	TiDBOpt3StageDistinctAgg = "tidb_opt_three_stage_distinct_agg"

	// TiDBOptEnable3StageMultiDistinctAgg is used to indicate whether to plan and execute the multi distinct agg in 3 stages
	TiDBOptEnable3StageMultiDistinctAgg = "tidb_opt_enable_three_stage_multi_distinct_agg"

	TiDBOptExplainNoEvaledSubQuery = "tidb_opt_enable_non_eval_scalar_subquery"

	// TiDBBCJThresholdSize is used to limit the size of small table for mpp broadcast join.
	// Its unit is bytes, if the size of small table is larger than it, we will not use bcj.
	TiDBBCJThresholdSize = "tidb_broadcast_join_threshold_size"

	// TiDBBCJThresholdCount is used to limit the count of small table for mpp broadcast join.
	// If we can't estimate the size of one side of join child, we will check if its row number exceeds this limitation.
	TiDBBCJThresholdCount = "tidb_broadcast_join_threshold_count"

	// TiDBPreferBCJByExchangeDataSize indicates the method used to choose mpp broadcast join
	TiDBPreferBCJByExchangeDataSize = "tidb_prefer_broadcast_join_by_exchange_data_size"

	// TiDBOptWriteRowID is used to enable/disable the operations of insert、replace and update to _tidb_rowid.
	TiDBOptWriteRowID = "tidb_opt_write_row_id"

	// TiDBAutoAnalyzeRatio will run if (table modify count)/(table row count) is greater than this value.
	TiDBAutoAnalyzeRatio = "tidb_auto_analyze_ratio"

	// TiDBAutoAnalyzeStartTime will run if current time is within start time and end time.
	TiDBAutoAnalyzeStartTime = "tidb_auto_analyze_start_time"
	TiDBAutoAnalyzeEndTime   = "tidb_auto_analyze_end_time"

	// TiDBChecksumTableConcurrency is used to speed up the ADMIN CHECKSUM TABLE
	// statement, when a table has multiple indices, those indices can be
	// scanned concurrently, with the cost of higher system performance impact.
	TiDBChecksumTableConcurrency = "tidb_checksum_table_concurrency"

	// TiDBCurrentTS is used to get the current transaction timestamp.
	// It is read-only.
	TiDBCurrentTS = "tidb_current_ts"

	// TiDBLastTxnInfo is used to get the last transaction info within the current session.
	TiDBLastTxnInfo = "tidb_last_txn_info"

	// TiDBLastQueryInfo is used to get the last query info within the current session.
	TiDBLastQueryInfo = "tidb_last_query_info"

	// TiDBLastDDLInfo is used to get the last ddl info within the current session.
	TiDBLastDDLInfo = "tidb_last_ddl_info"

	// TiDBLastPlanReplayerToken is used to get the last plan replayer token within the current session
	TiDBLastPlanReplayerToken = "tidb_last_plan_replayer_token"

	// TiDBConfig is a read-only variable that shows the config of the current server.
	TiDBConfig = "tidb_config"

	// TiDBBatchInsert is used to enable/disable auto-split insert data. If set this option on, insert executor will automatically
	// insert data into multiple batches and use a single txn for each batch. This will be helpful when inserting large data.
	TiDBBatchInsert = "tidb_batch_insert"

	// TiDBBatchDelete is used to enable/disable auto-split delete data. If set this option on, delete executor will automatically
	// split data into multiple batches and use a single txn for each batch. This will be helpful when deleting large data.
	TiDBBatchDelete = "tidb_batch_delete"

	// TiDBBatchCommit is used to enable/disable auto-split the transaction.
	// If set this option on, the transaction will be committed when it reaches stmt-count-limit and starts a new transaction.
	TiDBBatchCommit = "tidb_batch_commit"

	// TiDBDMLBatchSize is used to split the insert/delete data into small batches.
	// It only takes effort when tidb_batch_insert/tidb_batch_delete is on.
	// Its default value is 20000. When the row size is large, 20k rows could be larger than 100MB.
	// User could change it to a smaller one to avoid breaking the transaction size limitation.
	TiDBDMLBatchSize = "tidb_dml_batch_size"

	// TiDBMemQuotaQuery controls the memory quota of a query.
	TiDBMemQuotaQuery = "tidb_mem_quota_query" // Bytes.
	// TiDBMemQuotaApplyCache controls the memory quota of a query.
	TiDBMemQuotaApplyCache = "tidb_mem_quota_apply_cache"

	// TiDBGeneralLog is used to log every query in the server in info level.
	TiDBGeneralLog = "tidb_general_log"

	// TiDBLogFileMaxDays is used to log every query in the server in info level.
	TiDBLogFileMaxDays = "tidb_log_file_max_days"

	// TiDBPProfSQLCPU is used to add label sql label to pprof result.
	TiDBPProfSQLCPU = "tidb_pprof_sql_cpu"

	// TiDBRetryLimit is the maximum number of retries when committing a transaction.
	TiDBRetryLimit = "tidb_retry_limit"

	// TiDBDisableTxnAutoRetry disables transaction auto retry.
	// Deprecated: This variable is deprecated, please do not use this variable.
	TiDBDisableTxnAutoRetry = "tidb_disable_txn_auto_retry"

	// TiDBEnableChunkRPC enables TiDB to use Chunk format for coprocessor requests.
	TiDBEnableChunkRPC = "tidb_enable_chunk_rpc"

	// TiDBOptimizerSelectivityLevel is used to control the selectivity estimation level.
	TiDBOptimizerSelectivityLevel = "tidb_optimizer_selectivity_level"

	// TiDBOptimizerEnableNewOnlyFullGroupByCheck is used to open the newly only_full_group_by check by maintaining functional dependency.
	TiDBOptimizerEnableNewOnlyFullGroupByCheck = "tidb_enable_new_only_full_group_by_check"

	TiDBOptimizerEnableOuterJoinReorder = "tidb_enable_outer_join_reorder"

	// TiDBOptimizerEnableNAAJ is used to open the newly null-aware anti join
	TiDBOptimizerEnableNAAJ = "tidb_enable_null_aware_anti_join"

	// TiDBTxnMode is used to control the transaction behavior.
	TiDBTxnMode = "tidb_txn_mode"

	// TiDBRowFormatVersion is used to control tidb row format version current.
	TiDBRowFormatVersion = "tidb_row_format_version"

	// TiDBEnableRowLevelChecksum is used to control whether to append checksum to row values.
	TiDBEnableRowLevelChecksum = "tidb_enable_row_level_checksum"

	// TiDBEnableTablePartition is used to control table partition feature.
	// The valid value include auto/on/off:
	// on or auto: enable table partition if the partition type is implemented.
	// off: always disable table partition.
	TiDBEnableTablePartition = "tidb_enable_table_partition"

	// TiDBEnableListTablePartition is used to control list table partition feature.
	// Deprecated: This variable is deprecated, please do not use this variable.
	TiDBEnableListTablePartition = "tidb_enable_list_partition"

	// TiDBSkipIsolationLevelCheck is used to control whether to return error when set unsupported transaction
	// isolation level.
	TiDBSkipIsolationLevelCheck = "tidb_skip_isolation_level_check"

	// TiDBLowResolutionTSO is used for reading data with low resolution TSO which is updated once every two seconds
	TiDBLowResolutionTSO = "tidb_low_resolution_tso"

	// TiDBReplicaRead is used for reading data from replicas, followers for example.
	TiDBReplicaRead = "tidb_replica_read"

	// TiDBAdaptiveClosestReadThreshold is for reading data from closest replicas(with same 'zone' label).
	// TiKV client should send read request to the closest replica(leader/follower) if the estimated response
	// size exceeds this threshold; otherwise, this request should be sent to leader.
	// This variable only take effect when `tidb_replica_read` is 'closest-adaptive'.
	TiDBAdaptiveClosestReadThreshold = "tidb_adaptive_closest_read_threshold"

	// TiDBAllowRemoveAutoInc indicates whether a user can drop the auto_increment column attribute or not.
	TiDBAllowRemoveAutoInc = "tidb_allow_remove_auto_inc"

	// TiDBMultiStatementMode enables multi statement at the risk of SQL injection
	// provides backwards compatibility
	TiDBMultiStatementMode = "tidb_multi_statement_mode"

	// TiDBEvolvePlanTaskMaxTime controls the max time of a single evolution task.
	TiDBEvolvePlanTaskMaxTime = "tidb_evolve_plan_task_max_time"

	// TiDBEvolvePlanTaskStartTime is the start time of evolution task.
	TiDBEvolvePlanTaskStartTime = "tidb_evolve_plan_task_start_time"
	// TiDBEvolvePlanTaskEndTime is the end time of evolution task.
	TiDBEvolvePlanTaskEndTime = "tidb_evolve_plan_task_end_time"

	// TiDBSlowLogThreshold is used to set the slow log threshold in the server.
	TiDBSlowLogThreshold = "tidb_slow_log_threshold"

	// TiDBSlowTxnLogThreshold is used to set the slow transaction log threshold in the server.
	TiDBSlowTxnLogThreshold = "tidb_slow_txn_log_threshold"

	// TiDBRecordPlanInSlowLog is used to log the plan of the slow query.
	TiDBRecordPlanInSlowLog = "tidb_record_plan_in_slow_log"

	// TiDBEnableSlowLog enables TiDB to log slow queries.
	TiDBEnableSlowLog = "tidb_enable_slow_log"

	// TiDBCheckMb4ValueInUTF8 is used to control whether to enable the check wrong utf8 value.
	TiDBCheckMb4ValueInUTF8 = "tidb_check_mb4_value_in_utf8"

	// TiDBFoundInPlanCache indicates whether the last statement was found in plan cache
	TiDBFoundInPlanCache = "last_plan_from_cache"

	// TiDBFoundInBinding indicates whether the last statement was matched with the hints in the binding.
	TiDBFoundInBinding = "last_plan_from_binding"

	// TiDBAllowAutoRandExplicitInsert indicates whether explicit insertion on auto_random column is allowed.
	TiDBAllowAutoRandExplicitInsert = "allow_auto_random_explicit_insert"

	// TiDBTxnScope indicates whether using global transactions or local transactions.
	TiDBTxnScope = "txn_scope"

	// TiDBTxnReadTS indicates the next transaction should be staleness transaction and provide the startTS
	TiDBTxnReadTS = "tx_read_ts"

	// TiDBReadStaleness indicates the staleness duration for following statement
	TiDBReadStaleness = "tidb_read_staleness"

	// TiDBEnablePaging indicates whether paging is enabled in coprocessor requests.
	TiDBEnablePaging = "tidb_enable_paging"

	// TiDBReadConsistency indicates whether the autocommit read statement goes through TiKV RC.
	TiDBReadConsistency = "tidb_read_consistency"

	// TiDBSysdateIsNow is the name of the `tidb_sysdate_is_now` system variable
	TiDBSysdateIsNow = "tidb_sysdate_is_now"

	// RequireSecureTransport indicates the secure mode for data transport
	RequireSecureTransport = "require_secure_transport"

	// TiFlashFastScan indicates whether use fast scan in tiflash.
	TiFlashFastScan = "tiflash_fastscan"

	// TiDBEnableUnsafeSubstitute indicates whether to enable generate column takes unsafe substitute.
	TiDBEnableUnsafeSubstitute = "tidb_enable_unsafe_substitute"

	// TiDBEnableTiFlashReadForWriteStmt indicates whether to enable TiFlash to read for write statements.
	TiDBEnableTiFlashReadForWriteStmt = "tidb_enable_tiflash_read_for_write_stmt"

	// TiDBUseAlloc indicates whether the last statement used chunk alloc
	TiDBUseAlloc = "last_sql_use_alloc"

	// TiDBExplicitRequestSourceType indicates the source of the request, it's a complement of RequestSourceType.
	// The value maybe "lightning", "br", "dumpling" etc.
	TiDBExplicitRequestSourceType = "tidb_request_source_type"
)

TiDB system variable names that only in session scope.

View Source 
const (
	// TiDBBuildStatsConcurrency specifies the number of concurrent workers used for analyzing tables or partitions.
	// When multiple tables or partitions are specified in the analyze statement, TiDB will process them concurrently.
	// Additionally, this setting controls the concurrency for building NDV (Number of Distinct Values) for special indexes,
	// such as generated columns composed indexes.
	TiDBBuildStatsConcurrency = "tidb_build_stats_concurrency"

	// TiDBBuildSamplingStatsConcurrency is used to control the concurrency of building stats using sampling.
	// 1. The number of concurrent workers to merge FMSketches and Sample Data from different regions.
	// 2. The number of concurrent workers to build TopN and Histogram concurrently.
	TiDBBuildSamplingStatsConcurrency = "tidb_build_sampling_stats_concurrency"

	// TiDBDistSQLScanConcurrency is used to set the concurrency of a distsql scan task.
	// A distsql scan task can be a table scan or a index scan, which may be distributed to many TiKV nodes.
	// Higher concurrency may reduce latency, but with the cost of higher memory usage and system performance impact.
	// If the query has a LIMIT clause, high concurrency makes the system do much more work than needed.
	TiDBDistSQLScanConcurrency = "tidb_distsql_scan_concurrency"

	// TiDBAnalyzeDistSQLScanConcurrency is the number of concurrent workers to scan regions to collect statistics (FMSketch, Samples).
	// For auto analyze, the value is controlled by tidb_sysproc_scan_concurrency variable.
	TiDBAnalyzeDistSQLScanConcurrency = "tidb_analyze_distsql_scan_concurrency"

	// TiDBOptInSubqToJoinAndAgg is used to enable/disable the optimizer rule of rewriting IN subquery.
	TiDBOptInSubqToJoinAndAgg = "tidb_opt_insubq_to_join_and_agg"

	// TiDBOptPreferRangeScan is used to enable/disable the optimizer to always prefer range scan over table scan, ignoring their costs.
	TiDBOptPreferRangeScan = "tidb_opt_prefer_range_scan"

	// TiDBOptEnableCorrelationAdjustment is used to indicates if enable correlation adjustment.
	TiDBOptEnableCorrelationAdjustment = "tidb_opt_enable_correlation_adjustment"

	// TiDBOptLimitPushDownThreshold determines if push Limit or TopN down to TiKV forcibly.
	TiDBOptLimitPushDownThreshold = "tidb_opt_limit_push_down_threshold"

	// TiDBOptCorrelationThreshold is a guard to enable row count estimation using column order correlation.
	TiDBOptCorrelationThreshold = "tidb_opt_correlation_threshold"

	// TiDBOptCorrelationExpFactor is an exponential factor to control heuristic approach when tidb_opt_correlation_threshold is not satisfied.
	TiDBOptCorrelationExpFactor = "tidb_opt_correlation_exp_factor"

	// TiDBOptCPUFactor is the CPU cost of processing one expression for one row.
	TiDBOptCPUFactor = "tidb_opt_cpu_factor"
	// TiDBOptCopCPUFactor is the CPU cost of processing one expression for one row in coprocessor.
	TiDBOptCopCPUFactor = "tidb_opt_copcpu_factor"
	// TiDBOptTiFlashConcurrencyFactor is concurrency number of tiflash computation.
	TiDBOptTiFlashConcurrencyFactor = "tidb_opt_tiflash_concurrency_factor"
	// TiDBOptNetworkFactor is the network cost of transferring 1 byte data.
	TiDBOptNetworkFactor = "tidb_opt_network_factor"
	// TiDBOptScanFactor is the IO cost of scanning 1 byte data on TiKV.
	TiDBOptScanFactor = "tidb_opt_scan_factor"
	// TiDBOptDescScanFactor is the IO cost of scanning 1 byte data on TiKV in desc order.
	TiDBOptDescScanFactor = "tidb_opt_desc_factor"
	// TiDBOptSeekFactor is the IO cost of seeking the start value in a range on TiKV or TiFlash.
	TiDBOptSeekFactor = "tidb_opt_seek_factor"
	// TiDBOptMemoryFactor is the memory cost of storing one tuple.
	TiDBOptMemoryFactor = "tidb_opt_memory_factor"
	// TiDBOptDiskFactor is the IO cost of reading/writing one byte to temporary disk.
	TiDBOptDiskFactor = "tidb_opt_disk_factor"
	// TiDBOptConcurrencyFactor is the CPU cost of additional one goroutine.
	TiDBOptConcurrencyFactor = "tidb_opt_concurrency_factor"
	// TiDBOptForceInlineCTE is used to enable/disable inline CTE
	TiDBOptForceInlineCTE = "tidb_opt_force_inline_cte"

	// TiDBIndexJoinBatchSize is used to set the batch size of an index lookup join.
	// The index lookup join fetches batches of data from outer executor and constructs ranges for inner executor.
	// This value controls how much of data in a batch to do the index join.
	// Large value may reduce the latency but consumes more system resource.
	TiDBIndexJoinBatchSize = "tidb_index_join_batch_size"

	// TiDBIndexLookupSize is used for index lookup executor.
	// The index lookup executor first scan a batch of handles from a index, then use those handles to lookup the table
	// rows, this value controls how much of handles in a batch to do a lookup task.
	// Small value sends more RPCs to TiKV, consume more system resource.
	// Large value may do more work than needed if the query has a limit.
	TiDBIndexLookupSize = "tidb_index_lookup_size"

	// TiDBIndexLookupConcurrency is used for index lookup executor.
	// A lookup task may have 'tidb_index_lookup_size' of handles at maximum, the handles may be distributed
	// in many TiKV nodes, we execute multiple concurrent index lookup tasks concurrently to reduce the time
	// waiting for a task to finish.
	// Set this value higher may reduce the latency but consumes more system resource.
	// tidb_index_lookup_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBIndexLookupConcurrency = "tidb_index_lookup_concurrency"

	// TiDBIndexLookupJoinConcurrency is used for index lookup join executor.
	// IndexLookUpJoin starts "tidb_index_lookup_join_concurrency" inner workers
	// to fetch inner rows and join the matched (outer, inner) row pairs.
	// tidb_index_lookup_join_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBIndexLookupJoinConcurrency = "tidb_index_lookup_join_concurrency"

	// TiDBIndexSerialScanConcurrency is used for controlling the concurrency of index scan operation
	// when we need to keep the data output order the same as the order of index data.
	TiDBIndexSerialScanConcurrency = "tidb_index_serial_scan_concurrency"

	// TiDBMaxChunkSize is used to control the max chunk size during query execution.
	TiDBMaxChunkSize = "tidb_max_chunk_size"

	// TiDBAllowBatchCop means if we should send batch coprocessor to TiFlash. It can be set to 0, 1 and 2.
	// 0 means never use batch cop, 1 means use batch cop in case of aggregation and join, 2, means to force sending batch cop for any query.
	// The default value is 0
	TiDBAllowBatchCop = "tidb_allow_batch_cop"

	// TiDBShardRowIDBits means all the tables created in the current session will be sharded.
	// The default value is 0
	TiDBShardRowIDBits = "tidb_shard_row_id_bits"

	// TiDBPreSplitRegions means all the tables created in the current session will be pre-splited.
	// The default value is 0
	TiDBPreSplitRegions = "tidb_pre_split_regions"

	// TiDBAllowMPPExecution means if we should use mpp way to execute query or not.
	// Default value is `true`, means to be determined by the optimizer.
	// Value set to `false` means never use mpp.
	TiDBAllowMPPExecution = "tidb_allow_mpp"

	// TiDBAllowTiFlashCop means we only use MPP mode to query data.
	// Default value is `true`, means to be determined by the optimizer.
	// Value set to `false` means we may fall back to TiFlash cop plan if possible.
	TiDBAllowTiFlashCop = "tidb_allow_tiflash_cop"

	// TiDBHashExchangeWithNewCollation means if hash exchange is supported when new collation is on.
	// Default value is `true`, means support hash exchange when new collation is on.
	// Value set to `false` means not support hash exchange when new collation is on.
	TiDBHashExchangeWithNewCollation = "tidb_hash_exchange_with_new_collation"

	// TiDBEnforceMPPExecution means if we should enforce mpp way to execute query or not.
	// Default value is `false`, means to be determined by variable `tidb_allow_mpp`.
	// Value set to `true` means enforce use mpp.
	// Note if you want to set `tidb_enforce_mpp` to `true`, you must set `tidb_allow_mpp` to `true` first.
	TiDBEnforceMPPExecution = "tidb_enforce_mpp"

	// TiDBMaxTiFlashThreads is the maximum number of threads to execute the request which is pushed down to tiflash.
	// Default value is -1, means it will not be pushed down to tiflash.
	// If the value is bigger than -1, it will be pushed down to tiflash and used to create db context in tiflash.
	TiDBMaxTiFlashThreads = "tidb_max_tiflash_threads"

	// TiDBMaxBytesBeforeTiFlashExternalJoin is the maximum bytes used by a TiFlash join before spill to disk
	TiDBMaxBytesBeforeTiFlashExternalJoin = "tidb_max_bytes_before_tiflash_external_join"

	// TiDBMaxBytesBeforeTiFlashExternalGroupBy is the maximum bytes used by a TiFlash hash aggregation before spill to disk
	TiDBMaxBytesBeforeTiFlashExternalGroupBy = "tidb_max_bytes_before_tiflash_external_group_by"

	// TiDBMaxBytesBeforeTiFlashExternalSort is the maximum bytes used by a TiFlash sort/TopN before spill to disk
	TiDBMaxBytesBeforeTiFlashExternalSort = "tidb_max_bytes_before_tiflash_external_sort"

	// TiFlashMemQuotaQueryPerNode is the maximum bytes used by a TiFlash Query on each TiFlash node
	TiFlashMemQuotaQueryPerNode = "tiflash_mem_quota_query_per_node"

	// TiFlashQuerySpillRatio is the threshold that TiFlash will trigger auto spill when the memory usage is above this percentage
	TiFlashQuerySpillRatio = "tiflash_query_spill_ratio"

	// TiDBMPPStoreFailTTL is the unavailable time when a store is detected failed. During that time, tidb will not send any task to
	// TiFlash even though the failed TiFlash node has been recovered.
	TiDBMPPStoreFailTTL = "tidb_mpp_store_fail_ttl"

	// TiDBInitChunkSize is used to control the init chunk size during query execution.
	TiDBInitChunkSize = "tidb_init_chunk_size"

	// TiDBMinPagingSize is used to control the min paging size in the coprocessor paging protocol.
	TiDBMinPagingSize = "tidb_min_paging_size"

	// TiDBMaxPagingSize is used to control the max paging size in the coprocessor paging protocol.
	TiDBMaxPagingSize = "tidb_max_paging_size"

	// TiDBEnableCascadesPlanner is used to control whether to enable the cascades planner.
	TiDBEnableCascadesPlanner = "tidb_enable_cascades_planner"

	// TiDBSkipUTF8Check skips the UTF8 validate process, validate UTF8 has performance cost, if we can make sure
	// the input string values are valid, we can skip the check.
	TiDBSkipUTF8Check = "tidb_skip_utf8_check"

	// TiDBSkipASCIICheck skips the ASCII validate process
	// old tidb may already have fields with invalid ASCII bytes
	// disable ASCII validate can guarantee a safe replication
	TiDBSkipASCIICheck = "tidb_skip_ascii_check"

	// TiDBHashJoinConcurrency is used for hash join executor.
	// The hash join outer executor starts multiple concurrent join workers to probe the hash table.
	// tidb_hash_join_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBHashJoinConcurrency = "tidb_hash_join_concurrency"

	// TiDBProjectionConcurrency is used for projection operator.
	// This variable controls the worker number of projection operator.
	// tidb_projection_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBProjectionConcurrency = "tidb_projection_concurrency"

	// TiDBHashAggPartialConcurrency is used for hash agg executor.
	// The hash agg executor starts multiple concurrent partial workers to do partial aggregate works.
	// tidb_hashagg_partial_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBHashAggPartialConcurrency = "tidb_hashagg_partial_concurrency"

	// TiDBHashAggFinalConcurrency is used for hash agg executor.
	// The hash agg executor starts multiple concurrent final workers to do final aggregate works.
	// tidb_hashagg_final_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBHashAggFinalConcurrency = "tidb_hashagg_final_concurrency"

	// TiDBWindowConcurrency is used for window parallel executor.
	// tidb_window_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBWindowConcurrency = "tidb_window_concurrency"

	// TiDBMergeJoinConcurrency is used for merge join parallel executor
	TiDBMergeJoinConcurrency = "tidb_merge_join_concurrency"

	// TiDBStreamAggConcurrency is used for stream aggregation parallel executor.
	// tidb_stream_agg_concurrency is deprecated, use tidb_executor_concurrency instead.
	TiDBStreamAggConcurrency = "tidb_streamagg_concurrency"

	// TiDBIndexMergeIntersectionConcurrency is used for parallel worker of index merge intersection.
	TiDBIndexMergeIntersectionConcurrency = "tidb_index_merge_intersection_concurrency"

	// TiDBEnableParallelApply is used for parallel apply.
	TiDBEnableParallelApply = "tidb_enable_parallel_apply"

	// TiDBBackoffLockFast is used for tikv backoff base time in milliseconds.
	TiDBBackoffLockFast = "tidb_backoff_lock_fast"

	// TiDBBackOffWeight is used to control the max back off time in TiDB.
	// The default maximum back off time is a small value.
	// BackOffWeight could multiply it to let the user adjust the maximum time for retrying.
	// Only positive integers can be accepted, which means that the maximum back off time can only grow.
	TiDBBackOffWeight = "tidb_backoff_weight"

	// TiDBDDLReorgWorkerCount defines the count of ddl reorg workers.
	TiDBDDLReorgWorkerCount = "tidb_ddl_reorg_worker_cnt"

	// TiDBDDLFlashbackConcurrency defines the count of ddl flashback workers.
	TiDBDDLFlashbackConcurrency = "tidb_ddl_flashback_concurrency"

	// TiDBDDLReorgBatchSize defines the transaction batch size of ddl reorg workers.
	TiDBDDLReorgBatchSize = "tidb_ddl_reorg_batch_size"

	// TiDBDDLErrorCountLimit defines the count of ddl error limit.
	TiDBDDLErrorCountLimit = "tidb_ddl_error_count_limit"

	// TiDBDDLReorgPriority defines the operations' priority of adding indices.
	// It can be: PRIORITY_LOW, PRIORITY_NORMAL, PRIORITY_HIGH
	TiDBDDLReorgPriority = "tidb_ddl_reorg_priority"

	// TiDBDDLReorgMaxWriteSpeed defines the max write limitation for the lightning local backend
	TiDBDDLReorgMaxWriteSpeed = "tidb_ddl_reorg_max_write_speed"

	// TiDBEnableAutoIncrementInGenerated disables the mysql compatibility check on using auto-incremented columns in
	// expression indexes and generated columns described here https://dev.mysql.com/doc/refman/5.7/en/create-table-generated-columns.html for details.
	TiDBEnableAutoIncrementInGenerated = "tidb_enable_auto_increment_in_generated"

	// TiDBPlacementMode is used to control the mode for placement
	TiDBPlacementMode = "tidb_placement_mode"

	// TiDBMaxDeltaSchemaCount defines the max length of deltaSchemaInfos.
	// deltaSchemaInfos is a queue that maintains the history of schema changes.
	TiDBMaxDeltaSchemaCount = "tidb_max_delta_schema_count"

	// TiDBScatterRegion will scatter the regions for DDLs when it is "table" or "global", "" indicates not trigger scatter.
	TiDBScatterRegion = "tidb_scatter_region"

	// TiDBWaitSplitRegionFinish defines the split region behaviour is sync or async.
	TiDBWaitSplitRegionFinish = "tidb_wait_split_region_finish"

	// TiDBWaitSplitRegionTimeout uses to set the split and scatter region back off time.
	TiDBWaitSplitRegionTimeout = "tidb_wait_split_region_timeout"

	// TiDBForcePriority defines the operations' priority of all statements.
	// It can be "NO_PRIORITY", "LOW_PRIORITY", "HIGH_PRIORITY", "DELAYED"
	TiDBForcePriority = "tidb_force_priority"

	// TiDBConstraintCheckInPlace indicates to check the constraint when the SQL executing.
	// It could hurt the performance of bulking insert when it is ON.
	TiDBConstraintCheckInPlace = "tidb_constraint_check_in_place"

	// TiDBEnableWindowFunction is used to control whether to enable the window function.
	TiDBEnableWindowFunction = "tidb_enable_window_function"

	// TiDBEnablePipelinedWindowFunction is used to control whether to use pipelined window function, it only works when tidb_enable_window_function = true.
	TiDBEnablePipelinedWindowFunction = "tidb_enable_pipelined_window_function"

	// TiDBEnableStrictDoubleTypeCheck is used to control table field double type syntax check.
	TiDBEnableStrictDoubleTypeCheck = "tidb_enable_strict_double_type_check"

	// TiDBOptProjectionPushDown is used to control whether to pushdown projection to coprocessor.
	TiDBOptProjectionPushDown = "tidb_opt_projection_push_down"

	// TiDBEnableVectorizedExpression is used to control whether to enable the vectorized expression evaluation.
	TiDBEnableVectorizedExpression = "tidb_enable_vectorized_expression"

	// TiDBOptJoinReorderThreshold defines the threshold less than which
	// we'll choose a rather time-consuming algorithm to calculate the join order.
	TiDBOptJoinReorderThreshold = "tidb_opt_join_reorder_threshold"

	// TiDBSlowQueryFile indicates which slow query log file for SLOW_QUERY table to parse.
	TiDBSlowQueryFile = "tidb_slow_query_file"

	// TiDBEnableFastAnalyze indicates to use fast analyze.
	// Deprecated: This variable is deprecated, please do not use this variable.
	TiDBEnableFastAnalyze = "tidb_enable_fast_analyze"

	// TiDBExpensiveQueryTimeThreshold indicates the time threshold of expensive query.
	TiDBExpensiveQueryTimeThreshold = "tidb_expensive_query_time_threshold"

	// TiDBExpensiveTxnTimeThreshold indicates the time threshold of expensive transaction.
	TiDBExpensiveTxnTimeThreshold = "tidb_expensive_txn_time_threshold"

	// TiDBEnableIndexMerge indicates to generate IndexMergePath.
	TiDBEnableIndexMerge = "tidb_enable_index_merge"

	// TiDBEnableNoopFuncs set true will enable using fake funcs(like get_lock release_lock)
	TiDBEnableNoopFuncs = "tidb_enable_noop_functions"

	// TiDBEnableStmtSummary indicates whether the statement summary is enabled.
	TiDBEnableStmtSummary = "tidb_enable_stmt_summary"

	// TiDBStmtSummaryInternalQuery indicates whether the statement summary contain internal query.
	TiDBStmtSummaryInternalQuery = "tidb_stmt_summary_internal_query"

	// TiDBStmtSummaryRefreshInterval indicates the refresh interval in seconds for each statement summary.
	TiDBStmtSummaryRefreshInterval = "tidb_stmt_summary_refresh_interval"

	// TiDBStmtSummaryHistorySize indicates the history size of each statement summary.
	TiDBStmtSummaryHistorySize = "tidb_stmt_summary_history_size"

	// TiDBStmtSummaryMaxStmtCount indicates the max number of statements kept in memory.
	TiDBStmtSummaryMaxStmtCount = "tidb_stmt_summary_max_stmt_count"

	// TiDBStmtSummaryMaxSQLLength indicates the max length of displayed normalized sql and sample sql.
	TiDBStmtSummaryMaxSQLLength = "tidb_stmt_summary_max_sql_length"

	// TiDBIgnoreInlistPlanDigest enables TiDB to generate the same plan digest with SQL using different in-list arguments.
	TiDBIgnoreInlistPlanDigest = "tidb_ignore_inlist_plan_digest"

	// TiDBCapturePlanBaseline indicates whether the capture of plan baselines is enabled.
	TiDBCapturePlanBaseline = "tidb_capture_plan_baselines"

	// TiDBUsePlanBaselines indicates whether the use of plan baselines is enabled.
	TiDBUsePlanBaselines = "tidb_use_plan_baselines"

	// TiDBEvolvePlanBaselines indicates whether the evolution of plan baselines is enabled.
	TiDBEvolvePlanBaselines = "tidb_evolve_plan_baselines"

	// TiDBOptEnableFuzzyBinding indicates whether to enable the universal binding.
	TiDBOptEnableFuzzyBinding = "tidb_opt_enable_fuzzy_binding"

	// TiDBEnableExtendedStats indicates whether the extended statistics feature is enabled.
	TiDBEnableExtendedStats = "tidb_enable_extended_stats"

	// TiDBIsolationReadEngines indicates the tidb only read from the stores whose engine type is involved in IsolationReadEngines.
	// Now, only support TiKV and TiFlash.
	TiDBIsolationReadEngines = "tidb_isolation_read_engines"

	// TiDBStoreLimit indicates the limit of sending request to a store, 0 means without limit.
	TiDBStoreLimit = "tidb_store_limit"

	// TiDBMetricSchemaStep indicates the step when query metric schema.
	TiDBMetricSchemaStep = "tidb_metric_query_step"

	// TiDBCDCWriteSource indicates the following data is written by TiCDC if it is not 0.
	TiDBCDCWriteSource = "tidb_cdc_write_source"

	// TiDBMetricSchemaRangeDuration indicates the range duration when query metric schema.
	TiDBMetricSchemaRangeDuration = "tidb_metric_query_range_duration"

	// TiDBEnableCollectExecutionInfo indicates that whether execution info is collected.
	TiDBEnableCollectExecutionInfo = "tidb_enable_collect_execution_info"

	// TiDBExecutorConcurrency is used for controlling the concurrency of all types of executors.
	TiDBExecutorConcurrency = "tidb_executor_concurrency"

	// TiDBEnableClusteredIndex indicates if clustered index feature is enabled.
	TiDBEnableClusteredIndex = "tidb_enable_clustered_index"

	// TiDBEnableGlobalIndex means if we could create an global index on a partition table or not.
	// Deprecated, will always be ON
	TiDBEnableGlobalIndex = "tidb_enable_global_index"

	// TiDBPartitionPruneMode indicates the partition prune mode used.
	TiDBPartitionPruneMode = "tidb_partition_prune_mode"

	// TiDBRedactLog indicates that whether redact log.
	TiDBRedactLog = "tidb_redact_log"

	// TiDBRestrictedReadOnly is meant for the cloud admin to toggle the cluster read only
	TiDBRestrictedReadOnly = "tidb_restricted_read_only"

	// TiDBSuperReadOnly is tidb's variant of mysql's super_read_only, which has some differences from mysql's super_read_only.
	TiDBSuperReadOnly = "tidb_super_read_only"

	// TiDBShardAllocateStep indicates the max size of continuous rowid shard in one transaction.
	TiDBShardAllocateStep = "tidb_shard_allocate_step"
	// TiDBEnableTelemetry indicates that whether usage data report to PingCAP is enabled.
	// Deprecated: it is 'off' always since Telemetry has been removed from TiDB.
	TiDBEnableTelemetry = "tidb_enable_telemetry"

	// TiDBMemoryUsageAlarmRatio indicates the alarm threshold when memory usage of the tidb-server exceeds.
	TiDBMemoryUsageAlarmRatio = "tidb_memory_usage_alarm_ratio"

	// TiDBMemoryUsageAlarmKeepRecordNum indicates the number of saved alarm files.
	TiDBMemoryUsageAlarmKeepRecordNum = "tidb_memory_usage_alarm_keep_record_num"

	// TiDBEnableRateLimitAction indicates whether enabled ratelimit action
	TiDBEnableRateLimitAction = "tidb_enable_rate_limit_action"

	// TiDBEnableAsyncCommit indicates whether to enable the async commit feature.
	TiDBEnableAsyncCommit = "tidb_enable_async_commit"

	// TiDBEnable1PC indicates whether to enable the one-phase commit feature.
	TiDBEnable1PC = "tidb_enable_1pc"

	// TiDBGuaranteeLinearizability indicates whether to guarantee linearizability.
	TiDBGuaranteeLinearizability = "tidb_guarantee_linearizability"

	// TiDBAnalyzeVersion indicates how tidb collects the analyzed statistics and how use to it.
	TiDBAnalyzeVersion = "tidb_analyze_version"

	// TiDBAutoAnalyzePartitionBatchSize indicates the batch size for partition tables for auto analyze in dynamic mode
	// Deprecated: This variable is deprecated, please do not use this variable.
	TiDBAutoAnalyzePartitionBatchSize = "tidb_auto_analyze_partition_batch_size"

	// TiDBEnableIndexMergeJoin indicates whether to enable index merge join.
	TiDBEnableIndexMergeJoin = "tidb_enable_index_merge_join"

	// TiDBTrackAggregateMemoryUsage indicates whether track the memory usage of aggregate function.
	TiDBTrackAggregateMemoryUsage = "tidb_track_aggregate_memory_usage"

	// TiDBEnableExchangePartition indicates whether to enable exchange partition.
	TiDBEnableExchangePartition = "tidb_enable_exchange_partition"

	// TiDBAllowFallbackToTiKV indicates the engine types whose unavailability triggers fallback to TiKV.
	// Now we only support TiFlash.
	TiDBAllowFallbackToTiKV = "tidb_allow_fallback_to_tikv"

	// TiDBEnableTopSQL indicates whether the top SQL is enabled.
	TiDBEnableTopSQL = "tidb_enable_top_sql"

	// TiDBSourceID indicates the source ID of the TiDB server.
	TiDBSourceID = "tidb_source_id"

	// TiDBTopSQLMaxTimeSeriesCount indicates the max number of statements been collected in each time series.
	TiDBTopSQLMaxTimeSeriesCount = "tidb_top_sql_max_time_series_count"

	// TiDBTopSQLMaxMetaCount indicates the max capacity of the collect meta per second.
	TiDBTopSQLMaxMetaCount = "tidb_top_sql_max_meta_count"

	// TiDBEnableLocalTxn indicates whether to enable Local Txn.
	TiDBEnableLocalTxn = "tidb_enable_local_txn"

	// TiDBEnableMDL indicates whether to enable MDL.
	TiDBEnableMDL = "tidb_enable_metadata_lock"

	// TiDBTSOClientBatchMaxWaitTime indicates the max value of the TSO Batch Wait interval time of PD client.
	TiDBTSOClientBatchMaxWaitTime = "tidb_tso_client_batch_max_wait_time"

	// TiDBTxnCommitBatchSize is used to control the batch size of transaction commit related requests sent by TiDB to TiKV.
	// If a single transaction has a large amount of writes, you can increase the batch size to improve the batch effect,
	// setting too large will exceed TiKV's raft-entry-max-size limit and cause commit failure.
	TiDBTxnCommitBatchSize = "tidb_txn_commit_batch_size"

	// TiDBEnableTSOFollowerProxy indicates whether to enable the TSO Follower Proxy feature of PD client.
	TiDBEnableTSOFollowerProxy = "tidb_enable_tso_follower_proxy"

	// PDEnableFollowerHandleRegion indicates whether to enable the PD Follower handle region API.
	PDEnableFollowerHandleRegion = "pd_enable_follower_handle_region"

	// TiDBEnableOrderedResultMode indicates if stabilize query results.
	TiDBEnableOrderedResultMode = "tidb_enable_ordered_result_mode"

	// TiDBRemoveOrderbyInSubquery indicates whether to remove ORDER BY in subquery.
	TiDBRemoveOrderbyInSubquery = "tidb_remove_orderby_in_subquery"

	// TiDBEnablePseudoForOutdatedStats indicates whether use pseudo for outdated stats
	TiDBEnablePseudoForOutdatedStats = "tidb_enable_pseudo_for_outdated_stats"

	// TiDBRegardNULLAsPoint indicates whether regard NULL as point when optimizing
	TiDBRegardNULLAsPoint = "tidb_regard_null_as_point"

	// TiDBTmpTableMaxSize indicates the max memory size of temporary tables.
	TiDBTmpTableMaxSize = "tidb_tmp_table_max_size"

	// TiDBEnableLegacyInstanceScope indicates if instance scope can be set with SET SESSION.
	TiDBEnableLegacyInstanceScope = "tidb_enable_legacy_instance_scope"

	// TiDBTableCacheLease indicates the read lock lease of a cached table.
	TiDBTableCacheLease = "tidb_table_cache_lease"

	// TiDBStatsLoadSyncWait indicates the time sql execution will sync-wait for stats load.
	TiDBStatsLoadSyncWait = "tidb_stats_load_sync_wait"

	// TiDBEnableMutationChecker indicates whether to check data consistency for mutations
	TiDBEnableMutationChecker = "tidb_enable_mutation_checker"
	// TiDBTxnAssertionLevel indicates how strict the assertion will be, which helps to detect and preventing data &
	// index inconsistency problems.
	TiDBTxnAssertionLevel = "tidb_txn_assertion_level"

	// TiDBIgnorePreparedCacheCloseStmt indicates whether to ignore close-stmt commands for prepared statements.
	TiDBIgnorePreparedCacheCloseStmt = "tidb_ignore_prepared_cache_close_stmt"

	// TiDBEnableNewCostInterface is a internal switch to indicates whether to use the new cost calculation interface.
	TiDBEnableNewCostInterface = "tidb_enable_new_cost_interface"

	// TiDBCostModelVersion is a internal switch to indicates the cost model version.
	TiDBCostModelVersion = "tidb_cost_model_version"

	// TiDBIndexJoinDoubleReadPenaltyCostRate indicates whether to add some penalty cost to IndexJoin and how much of it.
	// IndexJoin can cause plenty of extra double read tasks, which consume lots of resources and take a long time.
	// Since the number of double read tasks is hard to estimated accurately, we leave this variable to let us can adjust this
	// part of cost manually.
	TiDBIndexJoinDoubleReadPenaltyCostRate = "tidb_index_join_double_read_penalty_cost_rate"

	// TiDBBatchPendingTiFlashCount indicates the maximum count of non-available TiFlash tables.
	TiDBBatchPendingTiFlashCount = "tidb_batch_pending_tiflash_count"

	// TiDBQueryLogMaxLen is used to set the max length of the query in the log.
	TiDBQueryLogMaxLen = "tidb_query_log_max_len"

	// TiDBEnableNoopVariables is used to indicate if noops appear in SHOW [GLOBAL] VARIABLES
	TiDBEnableNoopVariables = "tidb_enable_noop_variables"

	// TiDBNonTransactionalIgnoreError is used to ignore error in non-transactional DMLs.
	// When set to false, a non-transactional DML returns when it meets the first error.
	// When set to true, a non-transactional DML finishes all batches even if errors are met in some batches.
	TiDBNonTransactionalIgnoreError = "tidb_nontransactional_ignore_error"

	// Fine grained shuffle is disabled when TiFlashFineGrainedShuffleStreamCount is zero.
	TiFlashFineGrainedShuffleStreamCount = "tiflash_fine_grained_shuffle_stream_count"
	TiFlashFineGrainedShuffleBatchSize   = "tiflash_fine_grained_shuffle_batch_size"

	// TiDBSimplifiedMetrics controls whether to unregister some unused metrics.
	TiDBSimplifiedMetrics = "tidb_simplified_metrics"

	// TiDBMemoryDebugModeMinHeapInUse is used to set tidb memory debug mode trigger threshold.
	// When set to 0, the function is disabled.
	// When set to a negative integer, use memory debug mode to detect the issue of frequent allocation and release of memory.
	// We do not actively trigger gc, and check whether the `tracker memory * (1+bias ratio) > heap in use` each 5s.
	// When set to a positive integer, use memory debug mode to detect the issue of memory tracking inaccurate.
	// We trigger runtime.GC() each 5s, and check whether the `tracker memory * (1+bias ratio) > heap in use`.
	TiDBMemoryDebugModeMinHeapInUse = "tidb_memory_debug_mode_min_heap_inuse"
	// TiDBMemoryDebugModeAlarmRatio is used set tidb memory debug mode bias ratio. Treat memory bias less than this ratio as noise.
	TiDBMemoryDebugModeAlarmRatio = "tidb_memory_debug_mode_alarm_ratio"

	// TiDBEnableAnalyzeSnapshot indicates whether to read data on snapshot when collecting statistics.
	// When set to false, ANALYZE reads the latest data.
	// When set to true, ANALYZE reads data on the snapshot at the beginning of ANALYZE.
	TiDBEnableAnalyzeSnapshot = "tidb_enable_analyze_snapshot"

	// TiDBDefaultStrMatchSelectivity controls some special cardinality estimation strategy for string match functions (like and regexp).
	// When set to 0, Selectivity() will try to evaluate those functions with TopN and NULL in the stats to estimate,
	// and the default selectivity and the selectivity for the histogram part will be 0.1.
	// When set to (0, 1], Selectivity() will use the value of this variable as the default selectivity of those
	// functions instead of the selectionFactor (0.8).
	TiDBDefaultStrMatchSelectivity = "tidb_default_string_match_selectivity"

	// TiDBEnablePrepPlanCache indicates whether to enable prepared plan cache
	TiDBEnablePrepPlanCache = "tidb_enable_prepared_plan_cache"
	// TiDBPrepPlanCacheSize indicates the number of cached statements.
	// This variable is deprecated, use tidb_session_plan_cache_size instead.
	TiDBPrepPlanCacheSize = "tidb_prepared_plan_cache_size"
	// TiDBEnablePrepPlanCacheMemoryMonitor indicates whether to enable prepared plan cache monitor
	TiDBEnablePrepPlanCacheMemoryMonitor = "tidb_enable_prepared_plan_cache_memory_monitor"

	// TiDBEnableNonPreparedPlanCache indicates whether to enable non-prepared plan cache.
	TiDBEnableNonPreparedPlanCache = "tidb_enable_non_prepared_plan_cache"
	// TiDBEnableNonPreparedPlanCacheForDML indicates whether to enable non-prepared plan cache for DML statements.
	TiDBEnableNonPreparedPlanCacheForDML = "tidb_enable_non_prepared_plan_cache_for_dml"
	// TiDBNonPreparedPlanCacheSize controls the size of non-prepared plan cache.
	// This variable is deprecated, use tidb_session_plan_cache_size instead.
	TiDBNonPreparedPlanCacheSize = "tidb_non_prepared_plan_cache_size"
	// TiDBPlanCacheMaxPlanSize controls the maximum size of a plan that can be cached.
	TiDBPlanCacheMaxPlanSize = "tidb_plan_cache_max_plan_size"
	// TiDBPlanCacheInvalidationOnFreshStats controls if plan cache will be invalidated automatically when
	// related stats are analyzed after the plan cache is generated.
	TiDBPlanCacheInvalidationOnFreshStats = "tidb_plan_cache_invalidation_on_fresh_stats"
	// TiDBSessionPlanCacheSize controls the size of session plan cache.
	TiDBSessionPlanCacheSize = "tidb_session_plan_cache_size"

	// TiDBEnableInstancePlanCache indicates whether to enable instance plan cache.
	// If this variable is false, session-level plan cache will be used.
	TiDBEnableInstancePlanCache = "tidb_enable_instance_plan_cache"
	// TiDBInstancePlanCacheReservedPercentage indicates the percentage memory to evict.
	TiDBInstancePlanCacheReservedPercentage = "tidb_instance_plan_cache_reserved_percentage"
	// TiDBInstancePlanCacheMaxMemSize indicates the maximum memory size of instance plan cache.
	TiDBInstancePlanCacheMaxMemSize = "tidb_instance_plan_cache_max_size"

	// TiDBConstraintCheckInPlacePessimistic controls whether to skip certain kinds of pessimistic locks.
	TiDBConstraintCheckInPlacePessimistic = "tidb_constraint_check_in_place_pessimistic"

	// TiDBEnableForeignKey indicates whether to enable foreign key feature.
	// TODO(crazycs520): remove this after foreign key GA.
	TiDBEnableForeignKey = "tidb_enable_foreign_key"

	// TiDBOptRangeMaxSize is the max memory limit for ranges. When the optimizer estimates that the memory usage of complete
	// ranges would exceed the limit, it chooses less accurate ranges such as full range. 0 indicates that there is no memory
	// limit for ranges.
	TiDBOptRangeMaxSize = "tidb_opt_range_max_size"

	// TiDBOptAdvancedJoinHint indicates whether the join method hint is compatible with join order hint.
	TiDBOptAdvancedJoinHint = "tidb_opt_advanced_join_hint"
	// TiDBOptUseInvisibleIndexes indicates whether to use invisible indexes.
	TiDBOptUseInvisibleIndexes = "tidb_opt_use_invisible_indexes"
	// TiDBAnalyzePartitionConcurrency is the number of concurrent workers to save statistics to the system tables.
	TiDBAnalyzePartitionConcurrency = "tidb_analyze_partition_concurrency"
	// TiDBMergePartitionStatsConcurrency indicates the concurrency when merge partition stats into global stats
	TiDBMergePartitionStatsConcurrency = "tidb_merge_partition_stats_concurrency"
	// TiDBEnableAsyncMergeGlobalStats indicates whether to enable async merge global stats
	TiDBEnableAsyncMergeGlobalStats = "tidb_enable_async_merge_global_stats"
	// TiDBOptPrefixIndexSingleScan indicates whether to do some optimizations to avoid double scan for prefix index.
	// When set to true, `col is (not) null`(`col` is index prefix column) is regarded as index filter rather than table filter.
	TiDBOptPrefixIndexSingleScan = "tidb_opt_prefix_index_single_scan"

	// TiDBEnableExternalTSRead indicates whether to enable read through an external ts
	TiDBEnableExternalTSRead = "tidb_enable_external_ts_read"

	// TiDBEnablePlanReplayerCapture indicates whether to enable plan replayer capture
	TiDBEnablePlanReplayerCapture = "tidb_enable_plan_replayer_capture"

	// TiDBEnablePlanReplayerContinuousCapture indicates whether to enable continuous capture
	TiDBEnablePlanReplayerContinuousCapture = "tidb_enable_plan_replayer_continuous_capture"
	// TiDBEnableReusechunk indicates whether to enable chunk alloc
	TiDBEnableReusechunk = "tidb_enable_reuse_chunk"

	// TiDBStoreBatchSize indicates the batch size of coprocessor in the same store.
	TiDBStoreBatchSize = "tidb_store_batch_size"

	// MppExchangeCompressionMode indicates the data compression method in mpp exchange operator
	MppExchangeCompressionMode = "mpp_exchange_compression_mode"

	// MppVersion indicates the mpp-version used to build mpp plan
	MppVersion = "mpp_version"

	// TiDBPessimisticTransactionFairLocking controls whether fair locking for pessimistic transaction
	// is enabled.
	TiDBPessimisticTransactionFairLocking = "tidb_pessimistic_txn_fair_locking"

	// TiDBEnablePlanCacheForParamLimit controls whether prepare statement with parameterized limit can be cached
	TiDBEnablePlanCacheForParamLimit = "tidb_enable_plan_cache_for_param_limit"

	// TiDBEnableINLJoinInnerMultiPattern indicates whether enable multi pattern for inner side of inl join
	TiDBEnableINLJoinInnerMultiPattern = "tidb_enable_inl_join_inner_multi_pattern"

	// TiFlashComputeDispatchPolicy indicates how to dispatch task to tiflash_compute nodes.
	TiFlashComputeDispatchPolicy = "tiflash_compute_dispatch_policy"

	// TiDBEnablePlanCacheForSubquery controls whether prepare statement with subquery can be cached
	TiDBEnablePlanCacheForSubquery = "tidb_enable_plan_cache_for_subquery"

	// TiDBOptEnableLateMaterialization indicates whether to enable late materialization
	TiDBOptEnableLateMaterialization = "tidb_opt_enable_late_materialization"
	// TiDBLoadBasedReplicaReadThreshold is the wait duration threshold to enable replica read automatically.
	TiDBLoadBasedReplicaReadThreshold = "tidb_load_based_replica_read_threshold"

	// TiDBOptOrderingIdxSelThresh is the threshold for optimizer to consider the ordering index.
	TiDBOptOrderingIdxSelThresh = "tidb_opt_ordering_index_selectivity_threshold"

	// TiDBOptOrderingIdxSelRatio is the ratio the optimizer will assume applies when non indexed filtering rows are found
	// via the ordering index.
	TiDBOptOrderingIdxSelRatio = "tidb_opt_ordering_index_selectivity_ratio"

	// TiDBOptEnableMPPSharedCTEExecution indicates whether the optimizer try to build shared CTE scan during MPP execution.
	TiDBOptEnableMPPSharedCTEExecution = "tidb_opt_enable_mpp_shared_cte_execution"
	// TiDBOptFixControl makes the user able to control some details of the optimizer behavior.
	TiDBOptFixControl = "tidb_opt_fix_control"

	// TiFlashReplicaRead is used to set the policy of TiFlash replica read when the query needs the TiFlash engine.
	TiFlashReplicaRead = "tiflash_replica_read"

	// TiDBLockUnchangedKeys indicates whether to lock duplicate keys in INSERT IGNORE and REPLACE statements,
	// or unchanged unique keys in UPDATE statements, see PR #42210 and #42713
	TiDBLockUnchangedKeys = "tidb_lock_unchanged_keys"

	// TiDBFastCheckTable enables fast check table.
	TiDBFastCheckTable = "tidb_enable_fast_table_check"

	// TiDBAnalyzeSkipColumnTypes indicates the column types whose statistics would not be collected when executing the ANALYZE command.
	TiDBAnalyzeSkipColumnTypes = "tidb_analyze_skip_column_types"

	// TiDBEnableCheckConstraint indicates whether to enable check constraint feature.
	TiDBEnableCheckConstraint = "tidb_enable_check_constraint"

	// TiDBOptEnableHashJoin indicates whether to enable hash join.
	TiDBOptEnableHashJoin = "tidb_opt_enable_hash_join"

	// TiDBHashJoinVersion indicates whether to use hash join implementation v2.
	TiDBHashJoinVersion = "tidb_hash_join_version"

	// TiDBOptObjective indicates whether the optimizer should be more stable, predictable or more aggressive.
	// Please see comments of SessionVars.OptObjective for details.
	TiDBOptObjective = "tidb_opt_objective"

	// TiDBEnableParallelHashaggSpill is the name of the `tidb_enable_parallel_hashagg_spill` system variable
	TiDBEnableParallelHashaggSpill = "tidb_enable_parallel_hashagg_spill"

	// TiDBTxnEntrySizeLimit indicates the max size of a entry in membuf.
	TiDBTxnEntrySizeLimit = "tidb_txn_entry_size_limit"

	// TiDBSchemaCacheSize indicates the size of infoschema meta data which are cached in V2 implementation.
	TiDBSchemaCacheSize = "tidb_schema_cache_size"

	// DivPrecisionIncrement indicates the number of digits by which to increase the scale of the result of
	// division operations performed with the / operator.
	DivPrecisionIncrement = "div_precision_increment"

	// TiDBEnableSharedLockPromotion indicates whether the `select for share` statement would be executed
	// as `select for update` statements which do acquire pessimistic locks.
	TiDBEnableSharedLockPromotion = "tidb_enable_shared_lock_promotion"
)

TiDB system variable names that both in session and global scope.

View Source 
const (
	// TiDBGCEnable turns garbage collection on or OFF
	TiDBGCEnable = "tidb_gc_enable"
	// TiDBGCRunInterval sets the interval that GC runs
	TiDBGCRunInterval = "tidb_gc_run_interval"
	// TiDBGCLifetime sets the retention window of older versions
	TiDBGCLifetime = "tidb_gc_life_time"
	// TiDBGCConcurrency sets the concurrency of garbage collection. -1 = AUTO value
	TiDBGCConcurrency = "tidb_gc_concurrency"
	// TiDBGCScanLockMode enables the green GC feature (deprecated)
	TiDBGCScanLockMode = "tidb_gc_scan_lock_mode"
	// TiDBGCMaxWaitTime sets max time for gc advances the safepoint delayed by active transactions
	TiDBGCMaxWaitTime = "tidb_gc_max_wait_time"
	// TiDBEnableEnhancedSecurity restricts SUPER users from certain operations.
	TiDBEnableEnhancedSecurity = "tidb_enable_enhanced_security"
	// TiDBEnableHistoricalStats enables the historical statistics feature (default off)
	TiDBEnableHistoricalStats = "tidb_enable_historical_stats"
	// TiDBPersistAnalyzeOptions persists analyze options for later analyze and auto-analyze
	TiDBPersistAnalyzeOptions = "tidb_persist_analyze_options"
	// TiDBEnableColumnTracking enables collecting predicate columns.
	// DEPRECATED: This variable is deprecated, please do not use this variable.
	TiDBEnableColumnTracking = "tidb_enable_column_tracking"
	// TiDBAnalyzeColumnOptions specifies the default column selection strategy for both manual and automatic analyze operations.
	// It accepts two values:
	// `PREDICATE`: Analyze only the columns that are used in the predicates of the query.
	// `ALL`: Analyze all columns in the table.
	TiDBAnalyzeColumnOptions = "tidb_analyze_column_options"
	// TiDBDisableColumnTrackingTime records the last time TiDBEnableColumnTracking is set off.
	// It is used to invalidate the collected predicate columns after turning off TiDBEnableColumnTracking, which avoids physical deletion.
	// It doesn't have cache in memory, and we directly get/set the variable value from/to mysql.tidb.
	// DEPRECATED: This variable is deprecated, please do not use this variable.
	TiDBDisableColumnTrackingTime = "tidb_disable_column_tracking_time"
	// TiDBStatsLoadPseudoTimeout indicates whether to fallback to pseudo stats after load timeout.
	TiDBStatsLoadPseudoTimeout = "tidb_stats_load_pseudo_timeout"
	// TiDBMemQuotaBindingCache indicates the memory quota for the bind cache.
	TiDBMemQuotaBindingCache = "tidb_mem_quota_binding_cache"
	// TiDBRCReadCheckTS indicates the tso optimization for read-consistency read is enabled.
	TiDBRCReadCheckTS = "tidb_rc_read_check_ts"
	// TiDBRCWriteCheckTs indicates whether some special write statements don't get latest tso from PD at RC
	TiDBRCWriteCheckTs = "tidb_rc_write_check_ts"
	// TiDBCommitterConcurrency controls the number of running concurrent requests in the commit phase.
	TiDBCommitterConcurrency = "tidb_committer_concurrency"
	// TiDBEnableBatchDML enables batch dml.
	TiDBEnableBatchDML = "tidb_enable_batch_dml"
	// TiDBStatsCacheMemQuota records stats cache quota
	TiDBStatsCacheMemQuota = "tidb_stats_cache_mem_quota"
	// TiDBMemQuotaAnalyze indicates the memory quota for all analyze jobs.
	TiDBMemQuotaAnalyze = "tidb_mem_quota_analyze"
	// TiDBEnableAutoAnalyze determines whether TiDB executes automatic analysis.
	// In test, we disable it by default. See GlobalSystemVariableInitialValue for details.
	TiDBEnableAutoAnalyze = "tidb_enable_auto_analyze"
	// TiDBEnableAutoAnalyzePriorityQueue determines whether TiDB executes automatic analysis with priority queue.
	TiDBEnableAutoAnalyzePriorityQueue = "tidb_enable_auto_analyze_priority_queue"
	// TiDBMemOOMAction indicates what operation TiDB perform when a single SQL statement exceeds
	// the memory quota specified by tidb_mem_quota_query and cannot be spilled to disk.
	TiDBMemOOMAction = "tidb_mem_oom_action"
	// TiDBPrepPlanCacheMemoryGuardRatio is used to prevent [performance.max-memory] from being exceeded
	TiDBPrepPlanCacheMemoryGuardRatio = "tidb_prepared_plan_cache_memory_guard_ratio"
	// TiDBMaxAutoAnalyzeTime is the max time that auto analyze can run. If auto analyze runs longer than the value, it
	// will be killed. 0 indicates that there is no time limit.
	TiDBMaxAutoAnalyzeTime = "tidb_max_auto_analyze_time"
	// TiDBAutoAnalyzeConcurrency is the concurrency of the auto analyze
	TiDBAutoAnalyzeConcurrency = "tidb_auto_analyze_concurrency"
	// TiDBEnableDistTask indicates whether to enable the distributed execute background tasks(For example DDL, Import etc).
	TiDBEnableDistTask = "tidb_enable_dist_task"
	// TiDBEnableFastCreateTable indicates whether to enable the fast create table feature.
	TiDBEnableFastCreateTable = "tidb_enable_fast_create_table"
	// TiDBGenerateBinaryPlan indicates whether binary plan should be generated in slow log and statements summary.
	TiDBGenerateBinaryPlan = "tidb_generate_binary_plan"
	// TiDBEnableGCAwareMemoryTrack indicates whether to turn-on GC-aware memory track.
	TiDBEnableGCAwareMemoryTrack = "tidb_enable_gc_aware_memory_track"
	// TiDBEnableTmpStorageOnOOM controls whether to enable the temporary storage for some operators
	// when a single SQL statement exceeds the memory quota specified by the memory quota.
	TiDBEnableTmpStorageOnOOM = "tidb_enable_tmp_storage_on_oom"
	// TiDBDDLEnableFastReorg indicates whether to use lighting backfill process for adding index.
	TiDBDDLEnableFastReorg = "tidb_ddl_enable_fast_reorg"
	// TiDBDDLDiskQuota used to set disk quota for lightning add index.
	TiDBDDLDiskQuota = "tidb_ddl_disk_quota"
	// TiDBCloudStorageURI used to set a cloud storage uri for ddl add index and import into.
	TiDBCloudStorageURI = "tidb_cloud_storage_uri"
	// TiDBAutoBuildStatsConcurrency is the number of concurrent workers to automatically analyze tables or partitions.
	// It is very similar to the `tidb_build_stats_concurrency` variable, but it is used for the auto analyze feature.
	TiDBAutoBuildStatsConcurrency = "tidb_auto_build_stats_concurrency"
	// TiDBSysProcScanConcurrency is used to set the scan concurrency of for backend system processes, like auto-analyze.
	// For now, it controls the number of concurrent workers to scan regions to collect statistics (FMSketch, Samples).
	TiDBSysProcScanConcurrency = "tidb_sysproc_scan_concurrency"
	// TiDBServerMemoryLimit indicates the memory limit of the tidb-server instance.
	TiDBServerMemoryLimit = "tidb_server_memory_limit"
	// TiDBServerMemoryLimitSessMinSize indicates the minimal memory used of a session, that becomes a candidate for session kill.
	TiDBServerMemoryLimitSessMinSize = "tidb_server_memory_limit_sess_min_size"
	// TiDBServerMemoryLimitGCTrigger indicates the gc percentage of the TiDBServerMemoryLimit.
	TiDBServerMemoryLimitGCTrigger = "tidb_server_memory_limit_gc_trigger"
	// TiDBEnableGOGCTuner is to enable GOGC tuner. it can tuner GOGC
	TiDBEnableGOGCTuner = "tidb_enable_gogc_tuner"
	// TiDBGOGCTunerThreshold is to control the threshold of GOGC tuner.
	TiDBGOGCTunerThreshold = "tidb_gogc_tuner_threshold"
	// TiDBGOGCTunerMaxValue is the max value of GOGC that GOGC tuner can change to.
	TiDBGOGCTunerMaxValue = "tidb_gogc_tuner_max_value"
	// TiDBGOGCTunerMinValue is the min value of GOGC that GOGC tuner can change to.
	TiDBGOGCTunerMinValue = "tidb_gogc_tuner_min_value"
	// TiDBExternalTS is the ts to read through when the `TiDBEnableExternalTsRead` is on
	TiDBExternalTS = "tidb_external_ts"
	// TiDBTTLJobEnable is used to enable/disable scheduling ttl job
	TiDBTTLJobEnable = "tidb_ttl_job_enable"
	// TiDBTTLScanBatchSize is used to control the batch size in the SELECT statement for TTL jobs
	TiDBTTLScanBatchSize = "tidb_ttl_scan_batch_size"
	// TiDBTTLDeleteBatchSize is used to control the batch size in the DELETE statement for TTL jobs
	TiDBTTLDeleteBatchSize = "tidb_ttl_delete_batch_size"
	// TiDBTTLDeleteRateLimit is used to control the delete rate limit for TTL jobs in each node
	TiDBTTLDeleteRateLimit = "tidb_ttl_delete_rate_limit"
	// TiDBTTLJobScheduleWindowStartTime is used to restrict the start time of the time window of scheduling the ttl jobs.
	TiDBTTLJobScheduleWindowStartTime = "tidb_ttl_job_schedule_window_start_time"
	// TiDBTTLJobScheduleWindowEndTime is used to restrict the end time of the time window of scheduling the ttl jobs.
	TiDBTTLJobScheduleWindowEndTime = "tidb_ttl_job_schedule_window_end_time"
	// TiDBTTLScanWorkerCount indicates the count of the scan workers in each TiDB node
	TiDBTTLScanWorkerCount = "tidb_ttl_scan_worker_count"
	// TiDBTTLDeleteWorkerCount indicates the count of the delete workers in each TiDB node
	TiDBTTLDeleteWorkerCount = "tidb_ttl_delete_worker_count"
	// PasswordReuseHistory limit a few passwords to reuse.
	PasswordReuseHistory = "password_history"
	// PasswordReuseTime limit how long passwords can be reused.
	PasswordReuseTime = "password_reuse_interval"
	// TiDBHistoricalStatsDuration indicates the duration to remain tidb historical stats
	TiDBHistoricalStatsDuration = "tidb_historical_stats_duration"
	// TiDBEnableHistoricalStatsForCapture indicates whether use historical stats in plan replayer capture
	TiDBEnableHistoricalStatsForCapture = "tidb_enable_historical_stats_for_capture"
	// TiDBEnableResourceControl indicates whether resource control feature is enabled
	TiDBEnableResourceControl = "tidb_enable_resource_control"
	// TiDBResourceControlStrictMode indicates whether resource control strict mode is enabled.
	// When strict mode is enabled, user need certain privilege to change session or statement resource group.
	TiDBResourceControlStrictMode = "tidb_resource_control_strict_mode"
	// TiDBStmtSummaryEnablePersistent indicates whether to enable file persistence for stmtsummary.
	TiDBStmtSummaryEnablePersistent = "tidb_stmt_summary_enable_persistent"
	// TiDBStmtSummaryFilename indicates the file name written by stmtsummary.
	TiDBStmtSummaryFilename = "tidb_stmt_summary_filename"
	// TiDBStmtSummaryFileMaxDays indicates how many days the files written by stmtsummary will be kept.
	TiDBStmtSummaryFileMaxDays = "tidb_stmt_summary_file_max_days"
	// TiDBStmtSummaryFileMaxSize indicates the maximum size (in mb) of a single file written by stmtsummary.
	TiDBStmtSummaryFileMaxSize = "tidb_stmt_summary_file_max_size"
	// TiDBStmtSummaryFileMaxBackups indicates the maximum number of files written by stmtsummary.
	TiDBStmtSummaryFileMaxBackups = "tidb_stmt_summary_file_max_backups"
	// TiDBTTLRunningTasks limits the count of running ttl tasks. Default to 0, means 3 times the count of TiKV (or no
	// limitation, if the storage is not TiKV).
	TiDBTTLRunningTasks = "tidb_ttl_running_tasks"
	// AuthenticationLDAPSASLAuthMethodName defines the authentication method used by LDAP SASL authentication plugin
	AuthenticationLDAPSASLAuthMethodName = "authentication_ldap_sasl_auth_method_name"
	// AuthenticationLDAPSASLCAPath defines the ca certificate to verify LDAP connection in LDAP SASL authentication plugin
	AuthenticationLDAPSASLCAPath = "authentication_ldap_sasl_ca_path"
	// AuthenticationLDAPSASLTLS defines whether to use TLS connection in LDAP SASL authentication plugin
	AuthenticationLDAPSASLTLS = "authentication_ldap_sasl_tls"
	// AuthenticationLDAPSASLServerHost defines the server host of LDAP server for LDAP SASL authentication plugin
	AuthenticationLDAPSASLServerHost = "authentication_ldap_sasl_server_host"
	// AuthenticationLDAPSASLServerPort defines the port of LDAP server for LDAP SASL authentication plugin
	AuthenticationLDAPSASLServerPort = "authentication_ldap_sasl_server_port"
	// AuthenticationLDAPSASLReferral defines whether to enable LDAP referral for LDAP SASL authentication plugin
	AuthenticationLDAPSASLReferral = "authentication_ldap_sasl_referral"
	// AuthenticationLDAPSASLUserSearchAttr defines the attribute of username in LDAP server
	AuthenticationLDAPSASLUserSearchAttr = "authentication_ldap_sasl_user_search_attr"
	// AuthenticationLDAPSASLBindBaseDN defines the `dn` to search the users in. It's used to limit the search scope of TiDB.
	AuthenticationLDAPSASLBindBaseDN = "authentication_ldap_sasl_bind_base_dn"
	// AuthenticationLDAPSASLBindRootDN defines the `dn` of the user to login the LDAP server and perform search.
	AuthenticationLDAPSASLBindRootDN = "authentication_ldap_sasl_bind_root_dn"
	// AuthenticationLDAPSASLBindRootPWD defines the password of the user to login the LDAP server and perform search.
	AuthenticationLDAPSASLBindRootPWD = "authentication_ldap_sasl_bind_root_pwd"
	// AuthenticationLDAPSASLInitPoolSize defines the init size of connection pool to LDAP server for SASL plugin.
	AuthenticationLDAPSASLInitPoolSize = "authentication_ldap_sasl_init_pool_size"
	// AuthenticationLDAPSASLMaxPoolSize defines the max size of connection pool to LDAP server for SASL plugin.
	AuthenticationLDAPSASLMaxPoolSize = "authentication_ldap_sasl_max_pool_size"
	// AuthenticationLDAPSimpleAuthMethodName defines the authentication method used by LDAP Simple authentication plugin
	AuthenticationLDAPSimpleAuthMethodName = "authentication_ldap_simple_auth_method_name"
	// AuthenticationLDAPSimpleCAPath defines the ca certificate to verify LDAP connection in LDAP Simple authentication plugin
	AuthenticationLDAPSimpleCAPath = "authentication_ldap_simple_ca_path"
	// AuthenticationLDAPSimpleTLS defines whether to use TLS connection in LDAP Simple authentication plugin
	AuthenticationLDAPSimpleTLS = "authentication_ldap_simple_tls"
	// AuthenticationLDAPSimpleServerHost defines the server host of LDAP server for LDAP Simple authentication plugin
	AuthenticationLDAPSimpleServerHost = "authentication_ldap_simple_server_host"
	// AuthenticationLDAPSimpleServerPort defines the port of LDAP server for LDAP Simple authentication plugin
	AuthenticationLDAPSimpleServerPort = "authentication_ldap_simple_server_port"
	// AuthenticationLDAPSimpleReferral defines whether to enable LDAP referral for LDAP Simple authentication plugin
	AuthenticationLDAPSimpleReferral = "authentication_ldap_simple_referral"
	// AuthenticationLDAPSimpleUserSearchAttr defines the attribute of username in LDAP server
	AuthenticationLDAPSimpleUserSearchAttr = "authentication_ldap_simple_user_search_attr"
	// AuthenticationLDAPSimpleBindBaseDN defines the `dn` to search the users in. It's used to limit the search scope of TiDB.
	AuthenticationLDAPSimpleBindBaseDN = "authentication_ldap_simple_bind_base_dn"
	// AuthenticationLDAPSimpleBindRootDN defines the `dn` of the user to login the LDAP server and perform search.
	AuthenticationLDAPSimpleBindRootDN = "authentication_ldap_simple_bind_root_dn"
	// AuthenticationLDAPSimpleBindRootPWD defines the password of the user to login the LDAP server and perform search.
	AuthenticationLDAPSimpleBindRootPWD = "authentication_ldap_simple_bind_root_pwd"
	// AuthenticationLDAPSimpleInitPoolSize defines the init size of connection pool to LDAP server for SASL plugin.
	AuthenticationLDAPSimpleInitPoolSize = "authentication_ldap_simple_init_pool_size"
	// AuthenticationLDAPSimpleMaxPoolSize defines the max size of connection pool to LDAP server for SASL plugin.
	AuthenticationLDAPSimpleMaxPoolSize = "authentication_ldap_simple_max_pool_size"
	// TiDBRuntimeFilterTypeName the value of is string, a runtime filter type list split by ",", such as: "IN,MIN_MAX"
	TiDBRuntimeFilterTypeName = "tidb_runtime_filter_type"
	// TiDBRuntimeFilterModeName the mode of runtime filter, such as "OFF", "LOCAL"
	TiDBRuntimeFilterModeName = "tidb_runtime_filter_mode"
	// TiDBSkipMissingPartitionStats controls how to handle missing partition stats when merging partition stats to global stats.
	// When set to true, skip missing partition stats and continue to merge other partition stats to global stats.
	// When set to false, give up merging partition stats to global stats.
	TiDBSkipMissingPartitionStats = "tidb_skip_missing_partition_stats"
	// TiDBSessionAlias indicates the alias of a session which is used for tracing.
	TiDBSessionAlias = "tidb_session_alias"
	// TiDBServiceScope indicates the role for tidb for distributed task framework.
	TiDBServiceScope = "tidb_service_scope"
	// TiDBSchemaVersionCacheLimit defines the capacity size of domain infoSchema cache.
	TiDBSchemaVersionCacheLimit = "tidb_schema_version_cache_limit"
	// TiDBEnableTiFlashPipelineMode means if we should use pipeline model to execute query or not in tiflash.
	// It's deprecated and setting it will not have any effect.
	TiDBEnableTiFlashPipelineMode = "tidb_enable_tiflash_pipeline_model"
	// TiDBIdleTransactionTimeout indicates the maximum time duration a transaction could be idle, unit is second.
	// Any idle transaction will be killed after being idle for `tidb_idle_transaction_timeout` seconds.
	// This is similar to https://docs.percona.com/percona-server/5.7/management/innodb_kill_idle_trx.html and https://mariadb.com/kb/en/transaction-timeouts/
	TiDBIdleTransactionTimeout = "tidb_idle_transaction_timeout"
	// TiDBLowResolutionTSOUpdateInterval defines how often to refresh low resolution timestamps.
	TiDBLowResolutionTSOUpdateInterval = "tidb_low_resolution_tso_update_interval"
	// TiDBDMLType indicates the execution type of DML in TiDB.
	// The value can be STANDARD, BULK.
	// Currently, the BULK mode only affects auto-committed DML.
	TiDBDMLType = "tidb_dml_type"
	// TiFlashHashAggPreAggMode indicates the policy of 1st hashagg.
	TiFlashHashAggPreAggMode = "tiflash_hashagg_preaggregation_mode"
	// TiDBEnableLazyCursorFetch defines whether to enable the lazy cursor fetch. If it's `OFF`, all results of
	// of a cursor will be stored in the tidb node in `EXECUTE` command.
	TiDBEnableLazyCursorFetch = "tidb_enable_lazy_cursor_fetch"
	// TiDBTSOClientRPCMode controls how the TSO client performs the TSO RPC requests. It internally controls the
	// concurrency of the RPC. This variable provides an approach to tune the latency of getting timestamps from PD.
	TiDBTSOClientRPCMode = "tidb_tso_client_rpc_mode"
)
View Source 
const (
	// MaxConfigurableConcurrency is the maximum number of "threads" (goroutines) that can be specified
	// for any type of configuration item that has concurrent workers.
	MaxConfigurableConcurrency = 256

	// MaxShardRowIDBits is the maximum number of bits that can be used for row-id sharding.
	MaxShardRowIDBits = 15

	// MaxPreSplitRegions is the maximum number of regions that can be pre-split.
	MaxPreSplitRegions = 15
)
View Source 
const (
	DefHostname                             = "localhost"
	DefIndexLookupConcurrency               = ConcurrencyUnset
	DefIndexLookupJoinConcurrency           = ConcurrencyUnset
	DefIndexSerialScanConcurrency           = 1
	DefIndexJoinBatchSize                   = 25000
	DefIndexLookupSize                      = 20000
	DefDistSQLScanConcurrency               = 15
	DefAnalyzeDistSQLScanConcurrency        = 4
	DefBuildStatsConcurrency                = 2
	DefBuildSamplingStatsConcurrency        = 2
	DefAutoAnalyzeRatio                     = 0.5
	DefAutoAnalyzeStartTime                 = "00:00 +0000"
	DefAutoAnalyzeEndTime                   = "23:59 +0000"
	DefAutoIncrementIncrement               = 1
	DefAutoIncrementOffset                  = 1
	DefChecksumTableConcurrency             = 4
	DefSkipUTF8Check                        = false
	DefSkipASCIICheck                       = false
	DefOptAggPushDown                       = false
	DefOptDeriveTopN                        = false
	DefOptCartesianBCJ                      = 1
	DefOptMPPOuterJoinFixedBuildSide        = false
	DefOptWriteRowID                        = false
	DefOptEnableCorrelationAdjustment       = true
	DefOptLimitPushDownThreshold            = 100
	DefOptCorrelationThreshold              = 0.9
	DefOptCorrelationExpFactor              = 1
	DefOptCPUFactor                         = 3.0
	DefOptCopCPUFactor                      = 3.0
	DefOptTiFlashConcurrencyFactor          = 24.0
	DefOptNetworkFactor                     = 1.0
	DefOptScanFactor                        = 1.5
	DefOptDescScanFactor                    = 3.0
	DefOptSeekFactor                        = 20.0
	DefOptMemoryFactor                      = 0.001
	DefOptDiskFactor                        = 1.5
	DefOptConcurrencyFactor                 = 3.0
	DefOptForceInlineCTE                    = false
	DefOptInSubqToJoinAndAgg                = true
	DefOptPreferRangeScan                   = true
	DefBatchInsert                          = false
	DefBatchDelete                          = false
	DefBatchCommit                          = false
	DefCurretTS                             = 0
	DefInitChunkSize                        = 32
	DefMinPagingSize                        = int(paging.MinPagingSize)
	DefMaxPagingSize                        = int(paging.MaxPagingSize)
	DefMaxChunkSize                         = 1024
	DefDMLBatchSize                         = 0
	DefMaxPreparedStmtCount                 = -1
	DefWaitTimeout                          = 28800
	DefTiDBMemQuotaApplyCache               = 32 << 20 // 32MB.
	DefTiDBMemQuotaBindingCache             = 64 << 20 // 64MB.
	DefTiDBGeneralLog                       = false
	DefTiDBPProfSQLCPU                      = 0
	DefTiDBRetryLimit                       = 10
	DefTiDBDisableTxnAutoRetry              = true
	DefTiDBConstraintCheckInPlace           = false
	DefTiDBHashJoinConcurrency              = ConcurrencyUnset
	DefTiDBProjectionConcurrency            = ConcurrencyUnset
	DefBroadcastJoinThresholdSize           = 100 * 1024 * 1024
	DefBroadcastJoinThresholdCount          = 10 * 1024
	DefPreferBCJByExchangeDataSize          = false
	DefTiDBOptimizerSelectivityLevel        = 0
	DefTiDBOptimizerEnableNewOFGB           = false
	DefTiDBEnableOuterJoinReorder           = true
	DefTiDBEnableNAAJ                       = true
	DefTiDBAllowBatchCop                    = 1
	DefShardRowIDBits                       = 0
	DefPreSplitRegions                      = 0
	DefBlockEncryptionMode                  = "aes-128-ecb"
	DefTiDBAllowMPPExecution                = true
	DefTiDBAllowTiFlashCop                  = false
	DefTiDBHashExchangeWithNewCollation     = true
	DefTiDBEnforceMPPExecution              = false
	DefTiFlashMaxThreads                    = -1
	DefTiFlashMaxBytesBeforeExternalJoin    = -1
	DefTiFlashMaxBytesBeforeExternalGroupBy = -1
	DefTiFlashMaxBytesBeforeExternalSort    = -1
	DefTiFlashMemQuotaQueryPerNode          = 0
	DefTiFlashQuerySpillRatio               = 0.7
	DefTiDBEnableTiFlashPipelineMode        = true
	DefTiDBMPPStoreFailTTL                  = "60s"
	DefTiDBTxnMode                          = PessimisticTxnMode
	DefTiDBRowFormatV1                      = 1
	DefTiDBRowFormatV2                      = 2
	DefTiDBDDLReorgWorkerCount              = 4
	DefTiDBDDLReorgBatchSize                = 256
	DefTiDBDDLFlashbackConcurrency          = 64
	DefTiDBDDLErrorCountLimit               = 512
	DefTiDBDDLReorgMaxWriteSpeed            = 0
	DefTiDBMaxDeltaSchemaCount              = 1024
	DefTiDBPlacementMode                    = PlacementModeStrict
	DefTiDBEnableAutoIncrementInGenerated   = false
	DefTiDBHashAggPartialConcurrency        = ConcurrencyUnset
	DefTiDBHashAggFinalConcurrency          = ConcurrencyUnset
	DefTiDBWindowConcurrency                = ConcurrencyUnset
	DefTiDBMergeJoinConcurrency             = 1 // disable optimization by default
	DefTiDBStreamAggConcurrency             = 1
	DefTiDBForcePriority                    = mysql.NoPriority
	DefEnableWindowFunction                 = true
	DefEnablePipelinedWindowFunction        = true
	DefEnableStrictDoubleTypeCheck          = true
	DefEnableVectorizedExpression           = true
	DefTiDBOptJoinReorderThreshold          = 0
	DefTiDBDDLSlowOprThreshold              = 300
	DefTiDBUseFastAnalyze                   = false
	DefTiDBSkipIsolationLevelCheck          = false
	DefTiDBExpensiveQueryTimeThreshold      = 60      // 60s
	DefTiDBExpensiveTxnTimeThreshold        = 60 * 10 // 10 minutes
	DefTiDBScatterRegion                    = ScatterOff
	DefTiDBWaitSplitRegionFinish            = true
	DefWaitSplitRegionTimeout               = 300 // 300s
	DefTiDBEnableNoopFuncs                  = Off
	DefTiDBEnableNoopVariables              = true
	DefTiDBAllowRemoveAutoInc               = false
	DefTiDBUsePlanBaselines                 = true
	DefTiDBEvolvePlanBaselines              = false
	DefTiDBEvolvePlanTaskMaxTime            = 600 // 600s
	DefTiDBEvolvePlanTaskStartTime          = "00:00 +0000"
	DefTiDBEvolvePlanTaskEndTime            = "23:59 +0000"
	DefInnodbLockWaitTimeout                = 50 // 50s
	DefTiDBStoreLimit                       = 0
	DefTiDBMetricSchemaStep                 = 60 // 60s
	DefTiDBMetricSchemaRangeDuration        = 60 // 60s
	DefTiDBFoundInPlanCache                 = false
	DefTiDBFoundInBinding                   = false
	DefTiDBEnableCollectExecutionInfo       = true
	DefTiDBAllowAutoRandExplicitInsert      = false
	DefTiDBEnableClusteredIndex             = ClusteredIndexDefModeOn
	DefTiDBRedactLog                        = Off
	DefTiDBRestrictedReadOnly               = false
	DefTiDBSuperReadOnly                    = false
	DefTiDBShardAllocateStep                = math.MaxInt64
	DefTiDBEnableTelemetry                  = false
	DefTiDBEnableParallelApply              = false
	DefTiDBPartitionPruneMode               = "dynamic"
	DefTiDBEnableRateLimitAction            = false
	DefTiDBEnableAsyncCommit                = false
	DefTiDBEnable1PC                        = false
	DefTiDBGuaranteeLinearizability         = true
	DefTiDBAnalyzeVersion                   = 2
	// Deprecated: This variable is deprecated, please do not use this variable.
	DefTiDBAutoAnalyzePartitionBatchSize              = mysql.PartitionCountLimit
	DefTiDBEnableIndexMergeJoin                       = false
	DefTiDBTrackAggregateMemoryUsage                  = true
	DefCTEMaxRecursionDepth                           = 1000
	DefTiDBTmpTableMaxSize                            = 64 << 20 // 64MB.
	DefTiDBEnableLocalTxn                             = false
	DefTiDBTSOClientBatchMaxWaitTime                  = 0.0 // 0ms
	DefTiDBEnableTSOFollowerProxy                     = false
	DefPDEnableFollowerHandleRegion                   = false
	DefTiDBEnableOrderedResultMode                    = false
	DefTiDBEnablePseudoForOutdatedStats               = false
	DefTiDBRegardNULLAsPoint                          = true
	DefEnablePlacementCheck                           = true
	DefTimestamp                                      = "0"
	DefTimestampFloat                                 = 0.0
	DefTiDBEnableStmtSummary                          = true
	DefTiDBStmtSummaryInternalQuery                   = false
	DefTiDBStmtSummaryRefreshInterval                 = 1800
	DefTiDBStmtSummaryHistorySize                     = 24
	DefTiDBStmtSummaryMaxStmtCount                    = 3000
	DefTiDBStmtSummaryMaxSQLLength                    = 4096
	DefTiDBCapturePlanBaseline                        = Off
	DefTiDBIgnoreInlistPlanDigest                     = false
	DefTiDBEnableIndexMerge                           = true
	DefEnableLegacyInstanceScope                      = true
	DefTiDBTableCacheLease                            = 3 // 3s
	DefTiDBPersistAnalyzeOptions                      = true
	DefTiDBStatsLoadSyncWait                          = 100
	DefTiDBStatsLoadPseudoTimeout                     = true
	DefSysdateIsNow                                   = false
	DefTiDBEnableParallelHashaggSpill                 = true
	DefTiDBEnableMutationChecker                      = false
	DefTiDBTxnAssertionLevel                          = AssertionOffStr
	DefTiDBIgnorePreparedCacheCloseStmt               = false
	DefTiDBBatchPendingTiFlashCount                   = 4000
	DefRCReadCheckTS                                  = false
	DefTiDBRemoveOrderbyInSubquery                    = true
	DefTiDBSkewDistinctAgg                            = false
	DefTiDB3StageDistinctAgg                          = true
	DefTiDB3StageMultiDistinctAgg                     = false
	DefTiDBOptExplainEvaledSubquery                   = false
	DefTiDBReadStaleness                              = 0
	DefTiDBGCMaxWaitTime                              = 24 * 60 * 60
	DefMaxAllowedPacket                        uint64 = 67108864
	DefTiDBEnableBatchDML                             = false
	DefTiDBMemQuotaQuery                              = memory.DefMemQuotaQuery // 1GB
	DefTiDBStatsCacheMemQuota                         = 0
	MaxTiDBStatsCacheMemQuota                         = 1024 * 1024 * 1024 * 1024 // 1TB
	DefTiDBQueryLogMaxLen                             = 4096
	DefRequireSecureTransport                         = false
	DefTiDBCommitterConcurrency                       = 128
	DefTiDBBatchDMLIgnoreError                        = false
	DefTiDBMemQuotaAnalyze                            = -1
	DefTiDBEnableAutoAnalyze                          = true
	DefTiDBEnableAutoAnalyzePriorityQueue             = true
	DefTiDBAnalyzeColumnOptions                       = "PREDICATE"
	DefTiDBMemOOMAction                               = "CANCEL"
	DefTiDBMaxAutoAnalyzeTime                         = 12 * 60 * 60
	DefTiDBAutoAnalyzeConcurrency                     = 1
	DefTiDBEnablePrepPlanCache                        = true
	DefTiDBPrepPlanCacheSize                          = 100
	DefTiDBSessionPlanCacheSize                       = 100
	DefTiDBEnablePrepPlanCacheMemoryMonitor           = true
	DefTiDBPrepPlanCacheMemoryGuardRatio              = 0.1
	DefTiDBEnableWorkloadBasedLearning                = false
	DefTiDBWorkloadBasedLearningInterval              = 24 * time.Hour
	DefTiDBEnableDistTask                             = true
	DefTiDBEnableFastCreateTable                      = true
	DefTiDBSimplifiedMetrics                          = false
	DefTiDBEnablePaging                               = true
	DefTiFlashFineGrainedShuffleStreamCount           = 0
	DefStreamCountWhenMaxThreadsNotSet                = 8
	DefTiFlashFineGrainedShuffleBatchSize             = 8192
	DefAdaptiveClosestReadThreshold                   = 4096
	DefTiDBEnableAnalyzeSnapshot                      = false
	DefTiDBGenerateBinaryPlan                         = true
	DefEnableTiDBGCAwareMemoryTrack                   = false
	DefTiDBDefaultStrMatchSelectivity                 = 0.8
	DefTiDBEnableTmpStorageOnOOM                      = true
	DefTiDBEnableMDL                                  = true
	DefTiFlashFastScan                                = false
	DefMemoryUsageAlarmRatio                          = 0.7
	DefMemoryUsageAlarmKeepRecordNum                  = 5
	DefTiDBEnableFastReorg                            = true
	DefTiDBDDLDiskQuota                               = 100 * 1024 * 1024 * 1024 // 100GB
	DefExecutorConcurrency                            = 5
	DefTiDBEnableNonPreparedPlanCache                 = false
	DefTiDBEnableNonPreparedPlanCacheForDML           = false
	DefTiDBNonPreparedPlanCacheSize                   = 100
	DefTiDBPlanCacheMaxPlanSize                       = 2 * size.MB
	DefTiDBInstancePlanCacheMaxMemSize                = 100 * size.MB
	MinTiDBInstancePlanCacheMemSize                   = 100 * size.MB
	DefTiDBInstancePlanCacheReservedPercentage        = 0.1
	// MaxDDLReorgBatchSize is exported for testing.
	MaxDDLReorgBatchSize                  int32  = 10240
	MinDDLReorgBatchSize                  int32  = 32
	MinExpensiveQueryTimeThreshold        uint64 = 10 // 10s
	MinExpensiveTxnTimeThreshold          uint64 = 60 // 60s
	DefTiDBAutoBuildStatsConcurrency             = 1
	DefTiDBSysProcScanConcurrency                = 1
	DefTiDBRcWriteCheckTs                        = false
	DefTiDBForeignKeyChecks                      = true
	DefTiDBOptAdvancedJoinHint                   = true
	DefTiDBAnalyzePartitionConcurrency           = 2
	DefTiDBOptRangeMaxSize                       = 64 * int64(size.MB) // 64 MB
	DefTiDBCostModelVer                          = 2
	DefTiDBServerMemoryLimitSessMinSize          = 128 << 20
	DefTiDBMergePartitionStatsConcurrency        = 1
	DefTiDBServerMemoryLimitGCTrigger            = 0.7
	DefTiDBEnableGOGCTuner                       = true
	// DefTiDBGOGCTunerThreshold is to limit TiDBGOGCTunerThreshold.
	DefTiDBGOGCTunerThreshold                 float64 = 0.6
	DefTiDBGOGCMaxValue                               = 500
	DefTiDBGOGCMinValue                               = 100
	DefTiDBOptPrefixIndexSingleScan                   = true
	DefTiDBEnableAsyncMergeGlobalStats                = true
	DefTiDBExternalTS                                 = 0
	DefTiDBEnableExternalTSRead                       = false
	DefTiDBEnableReusechunk                           = true
	DefTiDBUseAlloc                                   = false
	DefTiDBEnablePlanReplayerCapture                  = true
	DefTiDBIndexMergeIntersectionConcurrency          = ConcurrencyUnset
	DefTiDBTTLJobEnable                               = true
	DefTiDBTTLScanBatchSize                           = 500
	DefTiDBTTLScanBatchMaxSize                        = 10240
	DefTiDBTTLScanBatchMinSize                        = 1
	DefTiDBTTLDeleteBatchSize                         = 100
	DefTiDBTTLDeleteBatchMaxSize                      = 10240
	DefTiDBTTLDeleteBatchMinSize                      = 1
	DefTiDBTTLDeleteRateLimit                         = 0
	DefTiDBTTLRunningTasks                            = -1
	DefPasswordReuseHistory                           = 0
	DefPasswordReuseTime                              = 0
	DefTiDBStoreBatchSize                             = 4
	DefTiDBHistoricalStatsDuration                    = 7 * 24 * time.Hour
	DefTiDBEnableHistoricalStatsForCapture            = false
	DefTiDBTTLJobScheduleWindowStartTime              = "00:00 +0000"
	DefTiDBTTLJobScheduleWindowEndTime                = "23:59 +0000"
	DefTiDBTTLScanWorkerCount                         = 4
	DefTiDBTTLDeleteWorkerCount                       = 4
	DefaultExchangeCompressionMode                    = kv.ExchangeCompressionModeUnspecified
	DefTiDBEnableResourceControl                      = true
	DefTiDBResourceControlStrictMode                  = true
	DefTiDBPessimisticTransactionFairLocking          = false
	DefTiDBEnablePlanCacheForParamLimit               = true
	DefTiDBEnableINLJoinMultiPattern                  = true
	DefTiFlashComputeDispatchPolicy                   = tiflashcompute.DispatchPolicyConsistentHashStr
	DefTiDBEnablePlanCacheForSubquery                 = true
	DefTiDBLoadBasedReplicaReadThreshold              = time.Second
	DefTiDBOptEnableLateMaterialization               = true
	DefTiDBOptOrderingIdxSelThresh                    = 0.0
	DefTiDBOptOrderingIdxSelRatio                     = -1
	DefTiDBOptEnableMPPSharedCTEExecution             = false
	DefTiDBPlanCacheInvalidationOnFreshStats          = true
	DefTiDBEnableRowLevelChecksum                     = false
	DefAuthenticationLDAPSASLAuthMethodName           = "SCRAM-SHA-1"
	DefAuthenticationLDAPSASLServerPort               = 389
	DefAuthenticationLDAPSASLTLS                      = false
	DefAuthenticationLDAPSASLUserSearchAttr           = "uid"
	DefAuthenticationLDAPSASLInitPoolSize             = 10
	DefAuthenticationLDAPSASLMaxPoolSize              = 1000
	DefAuthenticationLDAPSimpleAuthMethodName         = "SIMPLE"
	DefAuthenticationLDAPSimpleServerPort             = 389
	DefAuthenticationLDAPSimpleTLS                    = false
	DefAuthenticationLDAPSimpleUserSearchAttr         = "uid"
	DefAuthenticationLDAPSimpleInitPoolSize           = 10
	DefAuthenticationLDAPSimpleMaxPoolSize            = 1000
	DefTiFlashReplicaRead                             = tiflash.AllReplicaStr
	DefTiDBEnableFastCheckTable                       = true
	DefRuntimeFilterType                              = "IN"
	DefRuntimeFilterMode                              = "OFF"
	DefTiDBLockUnchangedKeys                          = true
	DefTiDBEnableCheckConstraint                      = false
	DefTiDBSkipMissingPartitionStats                  = true
	DefTiDBOptEnableHashJoin                          = true
	DefTiDBHashJoinVersion                            = joinversion.HashJoinVersionOptimized
	DefTiDBOptObjective                               = OptObjectiveModerate
	DefTiDBSchemaVersionCacheLimit                    = 16
	DefTiDBIdleTransactionTimeout                     = 0
	DefTiDBTxnEntrySizeLimit                          = 0
	DefTiDBSchemaCacheSize                            = 512 * 1024 * 1024
	DefTiDBLowResolutionTSOUpdateInterval             = 2000
	DefDivPrecisionIncrement                          = 4
	DefTiDBDMLType                                    = "STANDARD"
	DefGroupConcatMaxLen                              = uint64(1024)
	DefDefaultWeekFormat                              = "0"
	DefTiFlashPreAggMode                              = ForcePreAggStr
	DefTiDBEnableLazyCursorFetch                      = false
	DefOptEnableProjectionPushDown                    = true
	DefTiDBEnableSharedLockPromotion                  = false
	DefTiDBTSOClientRPCMode                           = TSOClientRPCModeDefault
)

Default TiDB system variable values.

View Source 
const (
	// ScopeNone means the system variable can not be changed dynamically.
	ScopeNone ScopeFlag = 0
	// ScopeGlobal means the system variable can be changed globally.
	ScopeGlobal ScopeFlag = 1 << 0
	// ScopeSession means the system variable can only be changed in current session.
	ScopeSession ScopeFlag = 1 << 1
	// ScopeInstance means it is similar to global but doesn't propagate to other TiDB servers.
	ScopeInstance ScopeFlag = 1 << 2

	// TypeStr is the default
	TypeStr TypeFlag = iota
	// TypeBool for boolean
	TypeBool
	// TypeInt for integer
	TypeInt
	// TypeEnum for Enum
	TypeEnum
	// TypeFloat for Double
	TypeFloat
	// TypeUnsigned for Unsigned integer
	TypeUnsigned
	// TypeTime for time of day (a TiDB extension)
	TypeTime
	// TypeDuration for a golang duration (a TiDB extension)
	TypeDuration

	// On is the canonical string for ON
	On = "ON"
	// Off is the canonical string for OFF
	Off = "OFF"
	// Warn means return warnings
	Warn = "WARN"
	// IntOnly means enable for int type
	IntOnly = "INT_ONLY"
	// Marker is a special log redact behavior
	Marker = "MARKER"

	// AssertionStrictStr is a choice of variable TiDBTxnAssertionLevel that means full assertions should be performed,
	// even if the performance might be slowed down.
	AssertionStrictStr = "STRICT"
	// AssertionFastStr is a choice of variable TiDBTxnAssertionLevel that means assertions that doesn't affect
	// performance should be performed.
	AssertionFastStr = "FAST"
	// AssertionOffStr is a choice of variable TiDBTxnAssertionLevel that means no assertion should be performed.
	AssertionOffStr = "OFF"
	// OOMActionCancel constants represents the valid action configurations for OOMAction "CANCEL".
	OOMActionCancel = "CANCEL"
	// OOMActionLog constants represents the valid action configurations for OOMAction "LOG".
	OOMActionLog = "LOG"

	// TSOClientRPCModeDefault is a choice of variable TiDBTSOClientRPCMode. In this mode, the TSO client sends batched
	// TSO requests serially.
	TSOClientRPCModeDefault = "DEFAULT"
	// TSOClientRPCModeParallel is a choice of variable TiDBTSOClientRPCMode. In this mode, the TSO client tries to
	// keep approximately 2 batched TSO requests running in parallel. This option tries to reduce the batch-waiting time
	// by half, at the expense of about twice the amount of TSO RPC calls.
	TSOClientRPCModeParallel = "PARALLEL"
	// TSOClientRPCModeParallelFast is a choice of variable TiDBTSOClientRPCMode. In this mode, the TSO client tries to
	// keep approximately 4 batched TSO requests running in parallel. This option tries to reduce the batch-waiting time
	// by 3/4, at the expense of about 4 times the amount of TSO RPC calls.
	TSOClientRPCModeParallelFast = "PARALLEL-FAST"
)
View Source 
const (
	GlobalConfigEnableTopSQL = "enable_resource_metering"
	GlobalConfigSourceID     = "source_id"
)

Global config name list.

View Source 
const (
	// OffInt is used by TiDBOptOnOffWarn
	OffInt = 0
	// OnInt is used TiDBOptOnOffWarn
	OnInt = 1
	// WarnInt is used by TiDBOptOnOffWarn
	WarnInt = 2
)
View Source 
const ConcurrencyUnset = -1

ConcurrencyUnset means the value the of the concurrency related variable is unset.

View Source 
const ConnStatusShutdown int32 = 2

ConnStatusShutdown indicates that the connection status is closed by server. This code is put here because of package imports, and this value is the original server.connStatusShutdown.

View Source 
const (

	// FullDayTimeFormat is the full format of analyze start time and end time.
	FullDayTimeFormat = "15:04 -0700"
)

Variables

View Source 
var (
	ErrSnapshotTooOld              = dbterror.ClassVariable.NewStd(mysql.ErrSnapshotTooOld)
	ErrUnsupportedValueForVar      = dbterror.ClassVariable.NewStd(mysql.ErrUnsupportedValueForVar)
	ErrUnknownSystemVar            = dbterror.ClassVariable.NewStd(mysql.ErrUnknownSystemVariable)
	ErrIncorrectScope              = dbterror.ClassVariable.NewStd(mysql.ErrIncorrectGlobalLocalVar)
	ErrUnknownTimeZone             = dbterror.ClassVariable.NewStd(mysql.ErrUnknownTimeZone)
	ErrReadOnly                    = dbterror.ClassVariable.NewStd(mysql.ErrVariableIsReadonly)
	ErrWrongValueForVar            = dbterror.ClassVariable.NewStd(mysql.ErrWrongValueForVar)
	ErrWrongTypeForVar             = dbterror.ClassVariable.NewStd(mysql.ErrWrongTypeForVar)
	ErrTruncatedWrongValue         = dbterror.ClassVariable.NewStd(mysql.ErrTruncatedWrongValue)
	ErrMaxPreparedStmtCountReached = dbterror.ClassVariable.NewStd(mysql.ErrMaxPreparedStmtCountReached)
	ErrUnsupportedIsolationLevel   = dbterror.ClassVariable.NewStd(mysql.ErrUnsupportedIsolationLevel)

	ErrNotValidPassword = dbterror.ClassExecutor.NewStd(mysql.ErrNotValidPassword)
	// ErrFunctionsNoopImpl is an error to say the behavior is protected by the tidb_enable_noop_functions sysvar.
	// This is copied from expression.ErrFunctionsNoopImpl to prevent circular dependencies.
	// It needs to be public for tests.
	ErrFunctionsNoopImpl                 = dbterror.ClassVariable.NewStdErr(mysql.ErrNotSupportedYet, pmysql.Message("function %s has only noop implementation in tidb now, use tidb_enable_noop_functions to enable these functions", nil))
	ErrVariableNoLongerSupported         = dbterror.ClassVariable.NewStd(mysql.ErrVariableNoLongerSupported)
	ErrInvalidDefaultUTF8MB4Collation    = dbterror.ClassVariable.NewStd(mysql.ErrInvalidDefaultUTF8MB4Collation)
	ErrWarnDeprecatedSyntaxNoReplacement = dbterror.ClassVariable.NewStdErr(mysql.ErrWarnDeprecatedSyntaxNoReplacement, pmysql.Message("Updating '%s' is deprecated. It will be made read-only in a future release.", nil))
	ErrWarnDeprecatedSyntaxSimpleMsg     = dbterror.ClassVariable.NewStdErr(mysql.ErrWarnDeprecatedSyntaxNoReplacement, pmysql.Message("%s is deprecated and will be removed in a future release.", nil))
)

Error instances.

View Source 
var (
	ProcessGeneralLog              = atomic.NewBool(false)
	RunAutoAnalyze                 = atomic.NewBool(DefTiDBEnableAutoAnalyze)
	EnableAutoAnalyzePriorityQueue = atomic.NewBool(DefTiDBEnableAutoAnalyzePriorityQueue)
	// AnalyzeColumnOptions is a global variable that indicates the default column choice for ANALYZE.
	// The value of this variable is a string that can be one of the following values:
	// "PREDICATE", "ALL".
	// The behavior of the analyze operation depends on the value of `tidb_persist_analyze_options`:
	// 1. If `tidb_persist_analyze_options` is enabled and the column choice from the analyze options record is set to `default`,
	//    the value of `tidb_analyze_column_options` determines the behavior of the analyze operation.
	// 2. If `tidb_persist_analyze_options` is disabled, `tidb_analyze_column_options` is used directly to decide
	//    whether to analyze all columns or just the predicate columns.
	AnalyzeColumnOptions  = atomic.NewString(DefTiDBAnalyzeColumnOptions)
	GlobalLogMaxDays      = atomic.NewInt32(int32(config.GetGlobalConfig().Log.File.MaxDays))
	QueryLogMaxLen        = atomic.NewInt32(DefTiDBQueryLogMaxLen)
	EnablePProfSQLCPU     = atomic.NewBool(false)
	EnableBatchDML        = atomic.NewBool(false)
	EnableTmpStorageOnOOM = atomic.NewBool(DefTiDBEnableTmpStorageOnOOM)

	DDLReorgMaxWriteSpeed = atomic.NewInt64(DefTiDBDDLReorgMaxWriteSpeed)

	// DDLSlowOprThreshold is the threshold for ddl slow operations, uint is millisecond.
	DDLSlowOprThreshold                  = config.GetGlobalConfig().Instance.DDLSlowOprThreshold
	ForcePriority                        = int32(DefTiDBForcePriority)
	MaxOfMaxAllowedPacket         uint64 = 1073741824
	ExpensiveQueryTimeThreshold   uint64 = DefTiDBExpensiveQueryTimeThreshold
	ExpensiveTxnTimeThreshold     uint64 = DefTiDBExpensiveTxnTimeThreshold
	MemoryUsageAlarmRatio                = atomic.NewFloat64(DefMemoryUsageAlarmRatio)
	MemoryUsageAlarmKeepRecordNum        = atomic.NewInt64(DefMemoryUsageAlarmKeepRecordNum)
	EnableLocalTxn                       = atomic.NewBool(DefTiDBEnableLocalTxn)
	MaxTSOBatchWaitInterval              = atomic.NewFloat64(DefTiDBTSOClientBatchMaxWaitTime)
	EnableTSOFollowerProxy               = atomic.NewBool(DefTiDBEnableTSOFollowerProxy)
	EnablePDFollowerHandleRegion         = atomic.NewBool(DefPDEnableFollowerHandleRegion)
	RestrictedReadOnly                   = atomic.NewBool(DefTiDBRestrictedReadOnly)
	VarTiDBSuperReadOnly                 = atomic.NewBool(DefTiDBSuperReadOnly)
	PersistAnalyzeOptions                = atomic.NewBool(DefTiDBPersistAnalyzeOptions)
	TableCacheLease                      = atomic.NewInt64(DefTiDBTableCacheLease)
	StatsLoadSyncWait                    = atomic.NewInt64(DefTiDBStatsLoadSyncWait)
	StatsLoadPseudoTimeout               = atomic.NewBool(DefTiDBStatsLoadPseudoTimeout)
	MemQuotaBindingCache                 = atomic.NewInt64(DefTiDBMemQuotaBindingCache)
	GCMaxWaitTime                        = atomic.NewInt64(DefTiDBGCMaxWaitTime)
	StatsCacheMemQuota                   = atomic.NewInt64(DefTiDBStatsCacheMemQuota)
	OOMAction                            = atomic.NewString(DefTiDBMemOOMAction)
	MaxAutoAnalyzeTime                   = atomic.NewInt64(DefTiDBMaxAutoAnalyzeTime)
	// variables for plan cache
	PreparedPlanCacheMemoryGuardRatio   = atomic.NewFloat64(DefTiDBPrepPlanCacheMemoryGuardRatio)
	EnableInstancePlanCache             = atomic.NewBool(false)
	InstancePlanCacheReservedPercentage = atomic.NewFloat64(0.1)
	InstancePlanCacheMaxMemSize         = atomic.NewInt64(int64(DefTiDBInstancePlanCacheMaxMemSize))
	EnableDistTask                      = atomic.NewBool(DefTiDBEnableDistTask)
	EnableFastCreateTable               = atomic.NewBool(DefTiDBEnableFastCreateTable)
	EnableNoopVariables                 = atomic.NewBool(DefTiDBEnableNoopVariables)
	EnableMDL                           = atomic.NewBool(false)
	AutoAnalyzePartitionBatchSize       = atomic.NewInt64(DefTiDBAutoAnalyzePartitionBatchSize)
	AutoAnalyzeConcurrency              = atomic.NewInt32(DefTiDBAutoAnalyzeConcurrency)
	// TODO: set value by session variable
	EnableWorkloadBasedLearning   = atomic.NewBool(DefTiDBEnableWorkloadBasedLearning)
	WorkloadBasedLearningInterval = atomic.NewDuration(DefTiDBWorkloadBasedLearningInterval)
	// EnableFastReorg indicates whether to use lightning to enhance DDL reorg performance.
	EnableFastReorg = atomic.NewBool(DefTiDBEnableFastReorg)
	// DDLDiskQuota is the temporary variable for set disk quota for lightning
	DDLDiskQuota = atomic.NewUint64(DefTiDBDDLDiskQuota)
	// EnableForeignKey indicates whether to enable foreign key feature.
	EnableForeignKey    = atomic.NewBool(true)
	EnableRCReadCheckTS = atomic.NewBool(false)
	// EnableRowLevelChecksum indicates whether to append checksum to row values.
	EnableRowLevelChecksum         = atomic.NewBool(DefTiDBEnableRowLevelChecksum)
	LowResolutionTSOUpdateInterval = atomic.NewUint32(DefTiDBLowResolutionTSOUpdateInterval)

	// DefTiDBServerMemoryLimit indicates the default value of TiDBServerMemoryLimit(TotalMem * 80%).
	// It should be a const and shouldn't be modified after tidb is started.
	DefTiDBServerMemoryLimit           = serverMemoryLimitDefaultValue()
	GOGCTunerThreshold                 = atomic.NewFloat64(DefTiDBGOGCTunerThreshold)
	PasswordValidationLength           = atomic.NewInt32(8)
	PasswordValidationMixedCaseCount   = atomic.NewInt32(1)
	PasswordValidtaionNumberCount      = atomic.NewInt32(1)
	PasswordValidationSpecialCharCount = atomic.NewInt32(1)
	EnableTTLJob                       = atomic.NewBool(DefTiDBTTLJobEnable)
	TTLScanBatchSize                   = atomic.NewInt64(DefTiDBTTLScanBatchSize)
	TTLDeleteBatchSize                 = atomic.NewInt64(DefTiDBTTLDeleteBatchSize)
	TTLDeleteRateLimit                 = atomic.NewInt64(DefTiDBTTLDeleteRateLimit)
	TTLJobScheduleWindowStartTime      = atomic.NewTime(
		mustParseTime(
			FullDayTimeFormat,
			DefTiDBTTLJobScheduleWindowStartTime,
		),
	)
	TTLJobScheduleWindowEndTime = atomic.NewTime(
		mustParseTime(
			FullDayTimeFormat,
			DefTiDBTTLJobScheduleWindowEndTime,
		),
	)
	TTLScanWorkerCount              = atomic.NewInt32(DefTiDBTTLScanWorkerCount)
	TTLDeleteWorkerCount            = atomic.NewInt32(DefTiDBTTLDeleteWorkerCount)
	PasswordHistory                 = atomic.NewInt64(DefPasswordReuseHistory)
	PasswordReuseInterval           = atomic.NewInt64(DefPasswordReuseTime)
	IsSandBoxModeEnabled            = atomic.NewBool(false)
	MaxPreparedStmtCountValue       = atomic.NewInt64(DefMaxPreparedStmtCount)
	HistoricalStatsDuration         = atomic.NewDuration(DefTiDBHistoricalStatsDuration)
	EnableHistoricalStatsForCapture = atomic.NewBool(DefTiDBEnableHistoricalStatsForCapture)
	TTLRunningTasks                 = atomic.NewInt32(DefTiDBTTLRunningTasks)
	// always set the default value to false because the resource control in kv-client is not inited
	// It will be initialized to the right value after the first call of `rebuildSysVarCache`
	EnableResourceControl           = atomic.NewBool(false)
	EnableResourceControlStrictMode = atomic.NewBool(true)
	EnableCheckConstraint           = atomic.NewBool(DefTiDBEnableCheckConstraint)
	SkipMissingPartitionStats       = atomic.NewBool(DefTiDBSkipMissingPartitionStats)
	TiFlashEnablePipelineMode       = atomic.NewBool(DefTiDBEnableTiFlashPipelineMode)
	ServiceScope                    = atomic.NewString("")
	SchemaVersionCacheLimit         = atomic.NewInt64(DefTiDBSchemaVersionCacheLimit)
	CloudStorageURI                 = atomic.NewString("")
	IgnoreInlistPlanDigest          = atomic.NewBool(DefTiDBIgnoreInlistPlanDigest)
	TxnEntrySizeLimit               = atomic.NewUint64(DefTiDBTxnEntrySizeLimit)

	SchemaCacheSize           = atomic.NewUint64(DefTiDBSchemaCacheSize)
	SchemaCacheSizeOriginText = atomic.NewString(strconv.Itoa(DefTiDBSchemaCacheSize))
)

Process global variables.

View Source 
var (
	// SetMemQuotaAnalyze is the func registered by global/subglobal tracker to set memory quota.
	SetMemQuotaAnalyze func(quota int64) = nil
	// GetMemQuotaAnalyze is the func registered by global/subglobal tracker to get memory quota.
	GetMemQuotaAnalyze func() int64 = nil
	// SetStatsCacheCapacity is the func registered by domain to set statsCache memory quota.
	SetStatsCacheCapacity atomic.Pointer[func(int64)]
	// SetPDClientDynamicOption is the func registered by domain
	SetPDClientDynamicOption atomic.Pointer[func(string, string) error]
	// SwitchMDL is the func registered by DDL to switch MDL.
	SwitchMDL func(bool2 bool) error = nil
	// EnableDDL is the func registered by ddl to enable running ddl in this instance.
	EnableDDL func() error = nil
	// DisableDDL is the func registered by ddl to disable running ddl in this instance.
	DisableDDL func() error = nil
	// SwitchFastCreateTable is the func registered by DDL to switch fast create table.
	SwitchFastCreateTable func(val bool) error
	// SetExternalTimestamp is the func registered by staleread to set externaltimestamp in pd
	SetExternalTimestamp func(ctx context.Context, ts uint64) error
	// GetExternalTimestamp is the func registered by staleread to get externaltimestamp from pd
	GetExternalTimestamp func(ctx context.Context) (uint64, error)
	// SetGlobalResourceControl is the func registered by domain to set cluster resource control.
	SetGlobalResourceControl atomic.Pointer[func(bool)]
	// ValidateCloudStorageURI validates the cloud storage URI.
	ValidateCloudStorageURI func(ctx context.Context, uri string) error
	// SetLowResolutionTSOUpdateInterval is the func registered by domain to set slow resolution tso update interval.
	SetLowResolutionTSOUpdateInterval func(interval time.Duration) error = nil
	// ChangeSchemaCacheSize is called when tidb_schema_cache_size is changed.
	ChangeSchemaCacheSize func(ctx context.Context, size uint64) error
	// EnableStatsOwner is the func registered by stats to enable running stats in this instance.
	EnableStatsOwner func() error = nil
	// DisableStatsOwner is the func registered by stats to disable running stats in this instance.
	DisableStatsOwner func() error = nil
)
View Source 
var (
	// EnableGlobalResourceControlFunc is the function registered by tikv_driver to set cluster resource control.
	EnableGlobalResourceControlFunc = func() {}
	// DisableGlobalResourceControlFunc is the function registered by tikv_driver to unset cluster resource control.
	DisableGlobalResourceControlFunc = func() {}
)

Hooks functions for Cluster Resource Control.

View Source 
var (
	// SchemaCacheSizeLowerBound will adjust the schema cache size to this value if
	// it is lower than this value.
	SchemaCacheSizeLowerBound uint64 = 64 * units.MiB
	// SchemaCacheSizeLowerBoundStr is the string representation of
	// SchemaCacheSizeLowerBound.
	SchemaCacheSizeLowerBoundStr = "64MB"
)
View Source 
var DefaultStatusVarScopeFlag = ScopeGlobal | ScopeSession

DefaultStatusVarScopeFlag is the default scope of status variables.

View Source 
var GAFunction4ExpressionIndex = map[string]struct{}{
	ast.Lower:      {},
	ast.Upper:      {},
	ast.MD5:        {},
	ast.Reverse:    {},
	ast.VitessHash: {},
	ast.TiDBShard:  {},

	ast.JSONType:          {},
	ast.JSONExtract:       {},
	ast.JSONUnquote:       {},
	ast.JSONArray:         {},
	ast.JSONObject:        {},
	ast.JSONSet:           {},
	ast.JSONInsert:        {},
	ast.JSONReplace:       {},
	ast.JSONRemove:        {},
	ast.JSONContains:      {},
	ast.JSONContainsPath:  {},
	ast.JSONValid:         {},
	ast.JSONArrayAppend:   {},
	ast.JSONArrayInsert:   {},
	ast.JSONMergePatch:    {},
	ast.JSONMergePreserve: {},
	ast.JSONPretty:        {},
	ast.JSONQuote:         {},
	ast.JSONSchemaValid:   {},
	ast.JSONSearch:        {},
	ast.JSONStorageSize:   {},
	ast.JSONDepth:         {},
	ast.JSONKeys:          {},
	ast.JSONLength:        {},
}

GAFunction4ExpressionIndex stores functions GA for expression index.

View Source 
var GenerateBinaryPlan atomic2.Bool

GenerateBinaryPlan decides whether we should record binary plan in slow log and stmt summary. It's controlled by the global variable `tidb_generate_binary_plan`.

View Source 
var (
	// PreparedStmtCount is exported for test.
	PreparedStmtCount int64
)
View Source 
var SetCharsetVariables = []string{
	CharacterSetClient,
	CharacterSetResults,
}

SetCharsetVariables is the system variable names related to set charset statements.

View Source 
var SetNamesVariables = []string{
	CharacterSetClient,
	CharacterSetConnection,
	CharacterSetResults,
}

SetNamesVariables is the system variable names related to set names statements.

Functions

func BoolToOnOff 

func BoolToOnOff(b bool) string

BoolToOnOff returns the string representation of a bool, i.e. "ON/OFF"

func CheckSysVarIsRemoved 

func CheckSysVarIsRemoved(varName string) error

CheckSysVarIsRemoved returns an error if the sysvar has been removed

func GetDDLErrorCountLimit 

func GetDDLErrorCountLimit() int64

GetDDLErrorCountLimit gets ddlErrorCountlimit size.

func GetDDLFlashbackConcurrency 

func GetDDLFlashbackConcurrency() int32

GetDDLFlashbackConcurrency gets ddlFlashbackConcurrency count.

func GetDDLReorgBatchSize 

func GetDDLReorgBatchSize() int32

GetDDLReorgBatchSize gets ddlReorgBatchSize.

func GetDDLReorgRowFormat 

func GetDDLReorgRowFormat() int64

GetDDLReorgRowFormat gets ddlReorgRowFormat version.

func GetDDLReorgWorkerCounter 

func GetDDLReorgWorkerCounter() int32

GetDDLReorgWorkerCounter gets ddlReorgWorkerCounter.

func GetMaxDeltaSchemaCount 

func GetMaxDeltaSchemaCount() int64

GetMaxDeltaSchemaCount gets maxDeltaSchemaCount size.

func GetStatusVars 

func GetStatusVars(vars *SessionVars) (map[string]*StatusVal, error)

GetStatusVars gets registered statistics status variables. TODO: Refactor this function to avoid repeated memory allocation / dealloc

func GetSysVars 

func GetSysVars() map[string]*SysVar

GetSysVars deep copies the sysVars list under a RWLock

func GlobalSystemVariableInitialValue 

func GlobalSystemVariableInitialValue(varName, varVal string) string

GlobalSystemVariableInitialValue gets the default value for a system variable including ones that are dynamically set (e.g. based on the store)

func IsAdaptiveReplicaReadEnabled 

func IsAdaptiveReplicaReadEnabled() bool

IsAdaptiveReplicaReadEnabled returns whether adaptive closest replica read can be enabled.

func IsRemovedSysVar 

func IsRemovedSysVar(varName string) bool

IsRemovedSysVar returns true if the sysvar has been removed

func OnOffToTrueFalse 

func OnOffToTrueFalse(str string) string

OnOffToTrueFalse convert "ON"/"OFF" to "true"/"false". In mysql.tidb the convention has been to store the string value "true"/"false", but sysvars use the convention ON/OFF.

func OrderByDependency 

func OrderByDependency(names map[string]string) []string

OrderByDependency orders the vars by dependency. The depended sys vars are in the front. Unknown sys vars are treated as not depended.

func ParseAnalyzeSkipColumnTypes 

func ParseAnalyzeSkipColumnTypes(val string) map[string]struct{}

ParseAnalyzeSkipColumnTypes converts tidb_analyze_skip_column_types to the map form.

func RegisterStatistics 

func RegisterStatistics(s Statistics)

RegisterStatistics registers statistics.

func RegisterSysVar 

func RegisterSysVar(sv *SysVar)

RegisterSysVar adds a sysvar to the SysVars list

func SetDDLErrorCountLimit 

func SetDDLErrorCountLimit(cnt int64)

SetDDLErrorCountLimit sets ddlErrorCountlimit size.

func SetDDLFlashbackConcurrency 

func SetDDLFlashbackConcurrency(cnt int32)

SetDDLFlashbackConcurrency sets ddlFlashbackConcurrency count. Sysvar validation enforces the range to already be correct.

func SetDDLReorgBatchSize 

func SetDDLReorgBatchSize(cnt int32)

SetDDLReorgBatchSize sets ddlReorgBatchSize size. Sysvar validation enforces the range to already be correct.

func SetDDLReorgRowFormat 

func SetDDLReorgRowFormat(format int64)

SetDDLReorgRowFormat sets ddlReorgRowFormat version.

func SetDDLReorgWorkerCounter 

func SetDDLReorgWorkerCounter(cnt int32)

SetDDLReorgWorkerCounter sets ddlReorgWorkerCounter count. Sysvar validation enforces the range to already be correct.

func SetEnableAdaptiveReplicaRead 

func SetEnableAdaptiveReplicaRead(enabled bool) bool

SetEnableAdaptiveReplicaRead set `enableAdaptiveReplicaRead` with given value. return true if the value is changed.

func SetMaxDeltaSchemaCount 

func SetMaxDeltaSchemaCount(cnt int64)

SetMaxDeltaSchemaCount sets maxDeltaSchemaCount size.

func SetSysVar 

func SetSysVar(name string, value string)

SetSysVar sets a sysvar. In fact, SysVar is immutable. SetSysVar is implemented by register a new SysVar with the same name again. This will not propagate to the cluster, so it should only be used for instance scoped AUTO variables such as system_time_zone.

func TiDBOptOn 

func TiDBOptOn(opt string) bool

TiDBOptOn could be used for all tidb session variable options, we use "ON"/1 to turn on those options.

func TiDBOptOnOffWarn 

func TiDBOptOnOffWarn(opt string) int

TiDBOptOnOffWarn converts On/Off/Warn to an int. It is used for MultiStmtMode and NoopFunctionsMode

func TidbOptInt 

func TidbOptInt(opt string, defaultVal int) int

TidbOptInt converts a string to an int

func TidbOptInt64 

func TidbOptInt64(opt string, defaultVal int64) int64

TidbOptInt64 converts a string to an int64

func TidbOptUint64 

func TidbOptUint64(opt string, defaultVal uint64) uint64

TidbOptUint64 converts a string to an uint64.

func ToTiPBTiFlashPreAggMode 

func ToTiPBTiFlashPreAggMode(mode string) (tipb.TiFlashPreAggMode, bool)

ToTiPBTiFlashPreAggMode return the corresponding tipb value of preaggregation mode.

func UnregisterStatistics 

func UnregisterStatistics(s Statistics)

UnregisterStatistics unregisters statistics.

func UnregisterSysVar 

func UnregisterSysVar(name string)

UnregisterSysVar removes a sysvar from the SysVars list currently only used in tests.

func ValidAnalyzeSkipColumnTypes 

func ValidAnalyzeSkipColumnTypes(val string) (string, error)

ValidAnalyzeSkipColumnTypes makes validation for tidb_analyze_skip_column_types.

func ValidTiFlashPreAggMode 

func ValidTiFlashPreAggMode() string

ValidTiFlashPreAggMode returns all valid modes.

Types

type AssertionLevel 

type AssertionLevel int

AssertionLevel controls the assertion that will be performed during transactions. 

const (
	// AssertionLevelOff indicates no assertion should be performed.
	AssertionLevelOff AssertionLevel = iota
	// AssertionLevelFast indicates assertions that doesn't affect performance should be performed.
	AssertionLevelFast
	// AssertionLevelStrict indicates full assertions should be performed, even if the performance might be slowed down.
	AssertionLevelStrict
)

type BatchSize 

type BatchSize struct {
	// IndexJoinBatchSize is the batch size of a index lookup join.
	IndexJoinBatchSize int

	// IndexLookupSize is the number of handles for an index lookup task in index double read executor.
	IndexLookupSize int

	// InitChunkSize defines init row count of a Chunk during query execution.
	InitChunkSize int

	// MaxChunkSize defines max row count of a Chunk during query execution.
	MaxChunkSize int

	// MinPagingSize defines the min size used by the coprocessor paging protocol.
	MinPagingSize int

	// MinPagingSize defines the max size used by the coprocessor paging protocol.
	MaxPagingSize int
}

BatchSize defines batch size values.

type ClusteredIndexDefMode 

type ClusteredIndexDefMode int

ClusteredIndexDefMode controls the default clustered property for primary key. 

const (
	// ClusteredIndexDefModeIntOnly indicates only single int primary key will default be clustered.
	ClusteredIndexDefModeIntOnly ClusteredIndexDefMode = 0
	// ClusteredIndexDefModeOn indicates primary key will default be clustered.
	ClusteredIndexDefModeOn ClusteredIndexDefMode = 1
	// ClusteredIndexDefModeOff indicates primary key will default be non-clustered.
	ClusteredIndexDefModeOff ClusteredIndexDefMode = 2
)

func TiDBOptEnableClustered 

func TiDBOptEnableClustered(opt string) ClusteredIndexDefMode

TiDBOptEnableClustered converts enable clustered options to ClusteredIndexDefMode.

type ColSize 

type ColSize struct {
	ColID int64
	Size  int64
}

ColSize is a data struct to store the delta information for a table.

type Concurrency 

type Concurrency struct {

	// ExecutorConcurrency is the number of concurrent worker for all executors.
	ExecutorConcurrency int

	// SourceAddr is the source address of request. Available in coprocessor ONLY.
	SourceAddr net.TCPAddr

	// IdleTransactionTimeout indicates the maximum time duration a transaction could be idle, unit is second.
	IdleTransactionTimeout int

	// BulkDMLEnabled indicates whether to enable bulk DML in pipelined mode.
	BulkDMLEnabled bool
	// contains filtered or unexported fields
}

Concurrency defines concurrency values.

func (*Concurrency) AnalyzeDistSQLScanConcurrency 

func (c *Concurrency) AnalyzeDistSQLScanConcurrency() int

AnalyzeDistSQLScanConcurrency return the number of concurrent dist SQL scan worker when to analyze.

func (*Concurrency) DistSQLScanConcurrency 

func (c *Concurrency) DistSQLScanConcurrency() int

DistSQLScanConcurrency return the number of concurrent dist SQL scan worker.

func (*Concurrency) HashAggFinalConcurrency 

func (c *Concurrency) HashAggFinalConcurrency() int

HashAggFinalConcurrency return the number of concurrent hash aggregation final worker.

func (*Concurrency) HashAggPartialConcurrency 

func (c *Concurrency) HashAggPartialConcurrency() int

HashAggPartialConcurrency return the number of concurrent hash aggregation partial worker.

func (*Concurrency) HashJoinConcurrency 

func (c *Concurrency) HashJoinConcurrency() int

HashJoinConcurrency return the number of concurrent hash join outer worker.

func (*Concurrency) IndexLookupConcurrency 

func (c *Concurrency) IndexLookupConcurrency() int

IndexLookupConcurrency return the number of concurrent index lookup worker.

func (*Concurrency) IndexLookupJoinConcurrency 

func (c *Concurrency) IndexLookupJoinConcurrency() int

IndexLookupJoinConcurrency return the number of concurrent index lookup join inner worker.

func (*Concurrency) IndexMergeIntersectionConcurrency 

func (c *Concurrency) IndexMergeIntersectionConcurrency() int

IndexMergeIntersectionConcurrency return the number of concurrent process worker.

func (*Concurrency) IndexSerialScanConcurrency 

func (c *Concurrency) IndexSerialScanConcurrency() int

IndexSerialScanConcurrency return the number of concurrent index serial scan worker. This option is not sync with ExecutorConcurrency since it's used by Analyze table.

func (*Concurrency) MergeJoinConcurrency 

func (c *Concurrency) MergeJoinConcurrency() int

MergeJoinConcurrency return the number of concurrent merge join worker.

func (*Concurrency) ProjectionConcurrency 

func (c *Concurrency) ProjectionConcurrency() int

ProjectionConcurrency return the number of concurrent projection worker.

func (*Concurrency) SetAnalyzeDistSQLScanConcurrency 

func (c *Concurrency) SetAnalyzeDistSQLScanConcurrency(n int)

SetAnalyzeDistSQLScanConcurrency set the number of concurrent dist SQL scan worker when to analyze.

func (*Concurrency) SetDistSQLScanConcurrency 

func (c *Concurrency) SetDistSQLScanConcurrency(n int)

SetDistSQLScanConcurrency set the number of concurrent dist SQL scan worker.

func (*Concurrency) SetHashAggFinalConcurrency 

func (c *Concurrency) SetHashAggFinalConcurrency(n int)

SetHashAggFinalConcurrency set the number of concurrent hash aggregation final worker.

func (*Concurrency) SetHashAggPartialConcurrency 

func (c *Concurrency) SetHashAggPartialConcurrency(n int)

SetHashAggPartialConcurrency set the number of concurrent hash aggregation partial worker.

func (*Concurrency) SetHashJoinConcurrency 

func (c *Concurrency) SetHashJoinConcurrency(n int)

SetHashJoinConcurrency set the number of concurrent hash join outer worker.

func (*Concurrency) SetIndexLookupConcurrency 

func (c *Concurrency) SetIndexLookupConcurrency(n int)

SetIndexLookupConcurrency set the number of concurrent index lookup worker.

func (*Concurrency) SetIndexLookupJoinConcurrency 

func (c *Concurrency) SetIndexLookupJoinConcurrency(n int)

SetIndexLookupJoinConcurrency set the number of concurrent index lookup join inner worker.

func (*Concurrency) SetIndexMergeIntersectionConcurrency 

func (c *Concurrency) SetIndexMergeIntersectionConcurrency(n int)

SetIndexMergeIntersectionConcurrency set the number of concurrent intersection process worker.

func (*Concurrency) SetIndexSerialScanConcurrency 

func (c *Concurrency) SetIndexSerialScanConcurrency(n int)

SetIndexSerialScanConcurrency set the number of concurrent index serial scan worker.

func (*Concurrency) SetMergeJoinConcurrency 

func (c *Concurrency) SetMergeJoinConcurrency(n int)

SetMergeJoinConcurrency set the number of concurrent merge join worker.

func (*Concurrency) SetProjectionConcurrency 

func (c *Concurrency) SetProjectionConcurrency(n int)

SetProjectionConcurrency set the number of concurrent projection worker.

func (*Concurrency) SetStreamAggConcurrency 

func (c *Concurrency) SetStreamAggConcurrency(n int)

SetStreamAggConcurrency set the number of concurrent stream aggregation worker.

func (*Concurrency) SetWindowConcurrency 

func (c *Concurrency) SetWindowConcurrency(n int)

SetWindowConcurrency set the number of concurrent window worker.

func (*Concurrency) StreamAggConcurrency 

func (c *Concurrency) StreamAggConcurrency() int

StreamAggConcurrency return the number of concurrent stream aggregation worker.

func (*Concurrency) UnionConcurrency 

func (c *Concurrency) UnionConcurrency() int

UnionConcurrency return the num of concurrent union worker.

func (*Concurrency) WindowConcurrency 

func (c *Concurrency) WindowConcurrency() int

WindowConcurrency return the number of concurrent window worker.

type ConnectionInfo 

type ConnectionInfo struct {
	ConnectionID      uint64
	ConnectionType    string
	Host              string
	ClientIP          string
	ClientPort        string
	ServerID          int
	ServerIP          string
	ServerPort        int
	Duration          float64
	User              string
	ServerOSLoginUser string
	OSVersion         string
	ClientVersion     string
	ServerVersion     string
	SSLVersion        string
	PID               int
	DB                string
	AuthMethod        string
	Attributes        map[string]string
}

ConnectionInfo presents the connection information, which is mainly used by audit logs.

func (*ConnectionInfo) IsSecureTransport 

func (connInfo *ConnectionInfo) IsSecureTransport() bool

IsSecureTransport checks whether the connection is secure.

type DeltaCols 

type DeltaCols interface {
	// UpdateColSizeMap is used to update delta map for cols.
	UpdateColSizeMap(m map[int64]int64) map[int64]int64
}

DeltaCols is used to update the delta size for cols.

type DeltaColsMap 

type DeltaColsMap map[int64]int64

DeltaColsMap implements DeltaCols

func (DeltaColsMap) UpdateColSizeMap 

func (cols DeltaColsMap) UpdateColSizeMap(m map[int64]int64) map[int64]int64

UpdateColSizeMap implements DeltaCols

type GlobalVarAccessor 

type GlobalVarAccessor interface {
	// GetGlobalSysVar gets the global system variable value for name.
	GetGlobalSysVar(name string) (string, error)
	// SetGlobalSysVar sets the global system variable name to value.
	SetGlobalSysVar(ctx context.Context, name string, value string) error
	// SetGlobalSysVarOnly sets the global system variable without calling the validation function or updating aliases.
	SetGlobalSysVarOnly(ctx context.Context, name string, value string, updateLocal bool) error
	// GetTiDBTableValue gets a value from mysql.tidb for the key 'name'
	GetTiDBTableValue(name string) (string, error)
	// SetTiDBTableValue sets a value+comment for the mysql.tidb key 'name'
	SetTiDBTableValue(name, value, comment string) error
}

GlobalVarAccessor is the interface for accessing global scope system and status variables.

type HookContext 

type HookContext interface {
	GetStore() kv.Storage
}

HookContext contains the necessary variables for executing set/get hook

type JSONSQLWarnForSlowLog 

type JSONSQLWarnForSlowLog struct {
	Level   string
	Message string
	// IsExtra means this SQL Warn is expected to be recorded only under some conditions (like in EXPLAIN) and should
	// haven't been recorded as a warning now, but we recorded it anyway to help diagnostics.
	IsExtra bool `json:",omitempty"`
}

JSONSQLWarnForSlowLog helps to print the SQLWarn through the slow log in JSON format.

type LazyStmtText 

type LazyStmtText struct {
	SQL    string
	Redact string
	Params PlanCacheParamList
	Format func(string) string
	// contains filtered or unexported fields
}

LazyStmtText represents the sql text of a stmt that used in log. It's lazily evaluated to reduce the mem allocs.

func (*LazyStmtText) SetText 

func (s *LazyStmtText) SetText(text string)

SetText sets the text directly.

func (*LazyStmtText) String 

func (s *LazyStmtText) String() string

String implements fmt.Stringer.

func (*LazyStmtText) Update 

func (s *LazyStmtText) Update(redact string, sql string, params *PlanCacheParamList)

Update resets the lazy text and leads to re-eval for next `s.String()`. It copies params so it's safe to use `SessionVars.PlanCacheParams` directly without worrying about the params get reset later.

type MemQuota 

type MemQuota struct {
	// MemQuotaQuery defines the memory quota for a query.
	MemQuotaQuery int64
	// MemQuotaApplyCache defines the memory capacity for apply cache.
	MemQuotaApplyCache int64
}

MemQuota defines memory quota values.

type MockGlobalAccessor 

type MockGlobalAccessor struct {
	SessionVars *SessionVars // can be overwritten if needed for correctness.
	// contains filtered or unexported fields
}

MockGlobalAccessor implements GlobalVarAccessor interface. it's used in tests

func NewMockGlobalAccessor 

func NewMockGlobalAccessor() *MockGlobalAccessor

NewMockGlobalAccessor implements GlobalVarAccessor interface.

func NewMockGlobalAccessor4Tests 

func NewMockGlobalAccessor4Tests() *MockGlobalAccessor

NewMockGlobalAccessor4Tests creates a new MockGlobalAccessor for use in the testsuite. It behaves like the real GlobalVarAccessor and has a list of sessionvars. Because we use the real GlobalVarAccessor outside of tests, this is unsafe to use by default (performance regression).

func (*MockGlobalAccessor) GetGlobalSysVar 

func (m *MockGlobalAccessor) GetGlobalSysVar(name string) (string, error)

GetGlobalSysVar implements GlobalVarAccessor.GetGlobalSysVar interface.

func (*MockGlobalAccessor) GetTiDBTableValue 

func (m *MockGlobalAccessor) GetTiDBTableValue(name string) (string, error)

GetTiDBTableValue implements GlobalVarAccessor.GetTiDBTableValue interface.

func (*MockGlobalAccessor) SetGlobalSysVar 

func (m *MockGlobalAccessor) SetGlobalSysVar(ctx context.Context, name string, value string) (err error)

SetGlobalSysVar implements GlobalVarAccessor.SetGlobalSysVar interface.

func (*MockGlobalAccessor) SetGlobalSysVarOnly 

func (m *MockGlobalAccessor) SetGlobalSysVarOnly(ctx context.Context, name string, value string, _ bool) error

SetGlobalSysVarOnly implements GlobalVarAccessor.SetGlobalSysVarOnly interface.

func (*MockGlobalAccessor) SetTiDBTableValue 

func (m *MockGlobalAccessor) SetTiDBTableValue(name, value, comment string) error

SetTiDBTableValue implements GlobalVarAccessor.SetTiDBTableValue interface.

type PartitionPruneMode 

type PartitionPruneMode string

PartitionPruneMode presents the prune mode used. 

const (
	// Static indicates only prune at plan phase.
	Static PartitionPruneMode = "static"
	// Dynamic indicates only prune at execute phase.
	Dynamic PartitionPruneMode = "dynamic"

	// StaticOnly is out-of-date.
	StaticOnly PartitionPruneMode = "static-only"
	// DynamicOnly is out-of-date.
	DynamicOnly PartitionPruneMode = "dynamic-only"
	// StaticButPrepareDynamic is out-of-date.
	StaticButPrepareDynamic PartitionPruneMode = "static-collect-dynamic"
)

func (PartitionPruneMode) Update 

func (p PartitionPruneMode) Update() PartitionPruneMode

Update updates out-of-date PruneMode.

func (PartitionPruneMode) Valid 

func (p PartitionPruneMode) Valid() bool

Valid indicate PruneMode is validated.

type PlanCacheParamList 

type PlanCacheParamList struct {
	// contains filtered or unexported fields
}

PlanCacheParamList stores the parameters for plan cache. Use attached methods to access or modify parameter values instead of accessing them directly.

func NewPlanCacheParamList 

func NewPlanCacheParamList() *PlanCacheParamList

NewPlanCacheParamList creates a new PlanCacheParams.

func (*PlanCacheParamList) AllParamValues 

func (p *PlanCacheParamList) AllParamValues() []types.Datum

AllParamValues returns all parameter values.

func (*PlanCacheParamList) Append 

func (p *PlanCacheParamList) Append(vs ...types.Datum)

Append appends a parameter value to the PlanCacheParams.

func (*PlanCacheParamList) GetParamValue 

func (p *PlanCacheParamList) GetParamValue(idx int) types.Datum

GetParamValue returns the value of the parameter at the specified index.

func (*PlanCacheParamList) Reset 

func (p *PlanCacheParamList) Reset()

Reset resets the PlanCacheParams.

func (*PlanCacheParamList) SetForNonPrepCache 

func (p *PlanCacheParamList) SetForNonPrepCache(flag bool)

SetForNonPrepCache sets the flag forNonPrepCache.

func (*PlanCacheParamList) String 

func (p *PlanCacheParamList) String() string

String implements the fmt.Stringer interface.

type ReadConsistencyLevel 

type ReadConsistencyLevel string

ReadConsistencyLevel is the level of read consistency. 

const (
	// ReadConsistencyStrict means read by strict consistency, default value.
	ReadConsistencyStrict ReadConsistencyLevel = "strict"
	// ReadConsistencyWeak means read can be weak consistency.
	ReadConsistencyWeak ReadConsistencyLevel = "weak"
)

func (ReadConsistencyLevel) IsWeak 

func (r ReadConsistencyLevel) IsWeak() bool

IsWeak returns true only if it's a weak-consistency read.

type RetryInfo 

type RetryInfo struct {
	Retrying               bool
	DroppedPreparedStmtIDs []uint32

	LastRcReadTS uint64
	// contains filtered or unexported fields
}

RetryInfo saves retry information.

func (*RetryInfo) AddAutoIncrementID 

func (r *RetryInfo) AddAutoIncrementID(id int64)

AddAutoIncrementID adds id to autoIncrementIDs.

func (*RetryInfo) AddAutoRandomID 

func (r *RetryInfo) AddAutoRandomID(id int64)

AddAutoRandomID adds id to autoRandomIDs.

func (*RetryInfo) Clean 

func (r *RetryInfo) Clean()

Clean does some clean work.

func (*RetryInfo) GetCurrAutoIncrementID 

func (r *RetryInfo) GetCurrAutoIncrementID() (int64, bool)

GetCurrAutoIncrementID gets current autoIncrementID.

func (*RetryInfo) GetCurrAutoRandomID 

func (r *RetryInfo) GetCurrAutoRandomID() (int64, bool)

GetCurrAutoRandomID gets current AutoRandomID.

func (*RetryInfo) ResetOffset 

func (r *RetryInfo) ResetOffset()

ResetOffset resets the current retry offset.

type RewritePhaseInfo 

type RewritePhaseInfo struct {
	// DurationRewrite is the duration of rewriting the SQL.
	DurationRewrite time.Duration

	// DurationPreprocessSubQuery is the duration of pre-processing sub-queries.
	DurationPreprocessSubQuery time.Duration

	// PreprocessSubQueries is the number of pre-processed sub-queries.
	PreprocessSubQueries int
}

RewritePhaseInfo records some information about the rewrite phase

func (*RewritePhaseInfo) Reset 

func (r *RewritePhaseInfo) Reset()

Reset resets all fields in RewritePhaseInfo.

type RowIDShardGenerator 

type RowIDShardGenerator struct {
	// contains filtered or unexported fields
}

RowIDShardGenerator is used to generate shard for row id.

func NewRowIDShardGenerator 

func NewRowIDShardGenerator(shardRand *rand.Rand, step int) *RowIDShardGenerator

NewRowIDShardGenerator creates a new RowIDShardGenerator.

func (*RowIDShardGenerator) GetCurrentShard 

func (s *RowIDShardGenerator) GetCurrentShard(count int) int64

GetCurrentShard returns the shard for the next `count` IDs.

func (*RowIDShardGenerator) GetShardStep 

func (s *RowIDShardGenerator) GetShardStep() int

GetShardStep returns the shard step

func (*RowIDShardGenerator) SetShardStep 

func (s *RowIDShardGenerator) SetShardStep(step int)

SetShardStep sets the step of shard

type RuntimeFilterMode 

type RuntimeFilterMode int64

RuntimeFilterMode the mode of runtime filter "OFF", "LOCAL" 

const (
	RFOff RuntimeFilterMode = iota + 1
	RFLocal
	RFGlobal
)

RFOff disable runtime filter RFLocal enable local runtime filter RFGlobal enable local and global runtime filter

func RuntimeFilterModeStringToMode 

func RuntimeFilterModeStringToMode(name string) (RuntimeFilterMode, bool)

RuntimeFilterModeStringToMode convert RuntimeFilterModeString to RuntimeFilterMode If name is legal, it will return Runtime Filter Mode and true Else, it will return -1 and false The second param means the convert is ok or not. True is ok, false means it is illegal name At present, we only support one name: "OFF", "LOCAL"

func (RuntimeFilterMode) String 

func (rfMode RuntimeFilterMode) String() string

String convert Runtime Filter Mode to String name

type RuntimeFilterType 

type RuntimeFilterType int64

RuntimeFilterType type of runtime filter "IN" 

const (
	In RuntimeFilterType = iota
	MinMax
)

In type of runtime filter, like "t.k1 in (?)" MinMax type of runtime filter, like "t.k1 < ? and t.k1 > ?"

func RuntimeFilterTypeStringToType 

func RuntimeFilterTypeStringToType(name string) (RuntimeFilterType, bool)

RuntimeFilterTypeStringToType convert RuntimeFilterTypeNameString to RuntimeFilterType If name is legal, it will return Runtime Filter Type and true Else, it will return -1 and false The second param means the convert is ok or not. True is ok, false means it is illegal name At present, we only support two names: "IN" and "MIN_MAX"

func ToRuntimeFilterType 

func ToRuntimeFilterType(sessionVarValue string) ([]RuntimeFilterType, bool)

ToRuntimeFilterType convert session var value to RuntimeFilterType list If sessionVarValue is legal, it will return RuntimeFilterType list and true The second param means the convert is ok or not. True is ok, false means it is illegal value The legal value should be comma-separated, eg: "IN,MIN_MAX"

func (RuntimeFilterType) String 

func (rfType RuntimeFilterType) String() string

String convert Runtime Filter Type to String name

type SavepointRecord 

type SavepointRecord struct {
	// name is the name of the savepoint
	Name string
	// MemDBCheckpoint is the transaction's memdb checkpoint.
	MemDBCheckpoint *tikv.MemDBCheckpoint
	// TxnCtxSavepoint is the savepoint of TransactionContext
	TxnCtxSavepoint TxnCtxNeedToRestore
}

SavepointRecord indicates a transaction's savepoint record.

type ScopeFlag 

type ScopeFlag uint8

ScopeFlag is for system variable whether can be changed in global/session dynamically or not.

func (ScopeFlag) String 

func (s ScopeFlag) String() string

type SequenceState 

type SequenceState struct {
	// contains filtered or unexported fields
}

SequenceState cache all sequence's latest value accessed by lastval() builtins. It's a session scoped variable, and all public methods of SequenceState are currently-safe.

func NewSequenceState 

func NewSequenceState() *SequenceState

NewSequenceState creates a SequenceState.

func (*SequenceState) GetAllStates 

func (ss *SequenceState) GetAllStates() map[int64]int64

GetAllStates returns a copied latestValueMap.

func (*SequenceState) GetLastValue 

func (ss *SequenceState) GetLastValue(sequenceID int64) (int64, bool, error)

GetLastValue will return last value of the specified sequenceID, bool(true) indicates the sequenceID is not in the cache map and NULL will be returned.

func (*SequenceState) SetAllStates 

func (ss *SequenceState) SetAllStates(latestValueMap map[int64]int64)

SetAllStates sets latestValueMap as a whole.

func (*SequenceState) UpdateState 

func (ss *SequenceState) UpdateState(sequenceID, value int64)

UpdateState will update the last value of specified sequenceID in a session.

type SessionVars 

type SessionVars struct {
	Concurrency
	MemQuota
	BatchSize
	// DMLBatchSize indicates the number of rows batch-committed for a statement.
	// It will be used when using LOAD DATA or BatchInsert or BatchDelete is on.
	DMLBatchSize        int
	RetryLimit          int64
	DisableTxnAutoRetry bool
	*UserVars

	// SysWarningCount is the system variable "warning_count", because it is on the hot path, so we extract it from the systems
	SysWarningCount int
	// SysErrorCount is the system variable "error_count", because it is on the hot path, so we extract it from the systems
	SysErrorCount uint16

	// PreparedStmts stores prepared statement.
	PreparedStmts        map[uint32]any
	PreparedStmtNameToID map[string]uint32

	// Parameter values for plan cache.
	PlanCacheParams   *PlanCacheParamList
	LastUpdateTime4PC types.Time

	// The Cached Plan for this execution, it should be *plannercore.PlanCacheValue.
	PlanCacheValue any

	// ActiveRoles stores active roles for current user
	ActiveRoles []*auth.RoleIdentity

	RetryInfo *RetryInfo
	// TxnCtx Should be reset on transaction finished.
	TxnCtx *TransactionContext
	// TxnCtxMu is used to protect TxnCtx.
	TxnCtxMu sync.Mutex

	// TxnManager is used to manage txn context in session
	TxnManager any

	// KVVars is the variables for KV storage.
	KVVars *tikvstore.Variables

	// ShardRowIDBits is the number of shard bits for user table row ID.
	ShardRowIDBits uint64

	// PreSplitRegions is the number of regions that should be pre-split for the table.
	PreSplitRegions uint64

	// ClientCapability is client's capability.
	ClientCapability uint32

	// TLSConnectionState is the TLS connection state (nil if not using TLS).
	TLSConnectionState *tls.ConnectionState

	// ConnectionID is the connection id of the current session.
	ConnectionID uint64

	// SQLCPUUsages records tidb/tikv cpu usages for current sql
	SQLCPUUsages ppcpuusage.SQLCPUUsages

	// PlanID is the unique id of logical and physical plan.
	PlanID atomic.Int32

	// PlanColumnID is the unique id for column when building plan.
	PlanColumnID atomic.Int64

	// MapScalarSubQ maps the scalar sub queries from its ID to its struct.
	MapScalarSubQ []any

	// MapHashCode2UniqueID4ExtendedCol map the expr's hash code to specified unique ID.
	MapHashCode2UniqueID4ExtendedCol map[string]int

	// User is the user identity with which the session login.
	User *auth.UserIdentity

	// Port is the port of the connected socket
	Port string

	// CurrentDB is the default database of this session.
	CurrentDB string

	// CurrentDBChanged indicates if the CurrentDB has been updated, and if it is we should print it into
	// the slow log to make it be compatible with MySQL, https://github.com/pingcap/tidb/issues/17846.
	CurrentDBChanged bool

	// CommonGlobalLoaded indicates if common global variable has been loaded for this session.
	CommonGlobalLoaded bool

	// InRestrictedSQL indicates if the session is handling restricted SQL execution.
	InRestrictedSQL bool

	// SnapshotTS is used for reading history data. For simplicity, SnapshotTS only supports distsql request.
	SnapshotTS uint64

	// TxnReadTS is used for staleness transaction, it provides next staleness transaction startTS.
	TxnReadTS *TxnReadTS

	// SnapshotInfoschema is used with SnapshotTS, when the schema version at snapshotTS less than current schema
	// version, we load an old version schema for query.
	SnapshotInfoschema any

	// GlobalVarsAccessor is used to set and get global variables.
	GlobalVarsAccessor GlobalVarAccessor

	// LastFoundRows is the number of found rows of last query statement
	LastFoundRows uint64

	// StmtCtx holds variables for current executing statement.
	StmtCtx *stmtctx.StatementContext

	// RefCountOfStmtCtx indicates the reference count of StmtCtx. When the
	// StmtCtx is accessed by other sessions, e.g. oom-alarm-handler/expensive-query-handler, add one first.
	// Note: this variable should be accessed and updated by atomic operations.
	RefCountOfStmtCtx stmtctx.ReferenceCount

	// AllowAggPushDown can be set to false to forbid aggregation push down.
	AllowAggPushDown bool

	// AllowDeriveTopN is used to enable/disable derived TopN optimization.
	AllowDeriveTopN bool

	// AllowCartesianBCJ means allow broadcast CARTESIAN join, 0 means not allow, 1 means allow broadcast CARTESIAN join
	// but the table size should under the broadcast threshold, 2 means allow broadcast CARTESIAN join even if the table
	// size exceeds the broadcast threshold
	AllowCartesianBCJ int

	// MPPOuterJoinFixedBuildSide means in MPP plan, always use right(left) table as build side for left(right) out join
	MPPOuterJoinFixedBuildSide bool

	// AllowDistinctAggPushDown can be set true to allow agg with distinct push down to tikv/tiflash.
	AllowDistinctAggPushDown bool

	// EnableSkewDistinctAgg can be set true to allow skew distinct aggregate rewrite
	EnableSkewDistinctAgg bool

	// Enable3StageDistinctAgg indicates whether to allow 3 stage distinct aggregate
	Enable3StageDistinctAgg bool

	// Enable3StageMultiDistinctAgg indicates whether to allow 3 stage multi distinct aggregate
	Enable3StageMultiDistinctAgg bool

	ExplainNonEvaledSubQuery bool

	// MultiStatementMode permits incorrect client library usage. Not recommended to be turned on.
	MultiStatementMode int

	// InMultiStmts indicates whether the statement is a multi-statement like `update t set a=1; update t set b=2;`.
	InMultiStmts bool

	// AllowWriteRowID variable is currently not recommended to be turned on.
	AllowWriteRowID bool

	// AllowBatchCop means if we should send batch coprocessor to TiFlash. Default value is 1, means to use batch cop in case of aggregation and join.
	// Value set to 2 means to force to send batch cop for any query. Value set to 0 means never use batch cop.
	AllowBatchCop int

	// HashExchangeWithNewCollation means if we support hash exchange when new collation is enabled.
	// Default value is `true`, means support hash exchange when new collation is enabled.
	// Value set to `false` means not use hash exchange when new collation is enabled.
	HashExchangeWithNewCollation bool

	// TiFlashMaxThreads is the maximum number of threads to execute the request which is pushed down to tiflash.
	// Default value is -1, means it will not be pushed down to tiflash.
	// If the value is bigger than -1, it will be pushed down to tiflash and used to create db context in tiflash.
	TiFlashMaxThreads int64

	// TiFlashMaxBytesBeforeExternalJoin is the maximum bytes used by a TiFlash join before spill to disk
	// Default value is -1, means it will not be pushed down to TiFlash
	// If the value is bigger than -1, it will be pushed down to TiFlash, and if the value is 0, it means
	// not limit and spill will never happen
	TiFlashMaxBytesBeforeExternalJoin int64

	// TiFlashMaxBytesBeforeExternalGroupBy is the maximum bytes used by a TiFlash hash aggregation before spill to disk
	// Default value is -1, means it will not be pushed down to TiFlash
	// If the value is bigger than -1, it will be pushed down to TiFlash, and if the value is 0, it means
	// not limit and spill will never happen
	TiFlashMaxBytesBeforeExternalGroupBy int64

	// TiFlashMaxBytesBeforeExternalSort is the maximum bytes used by a TiFlash sort/TopN before spill to disk
	// Default value is -1, means it will not be pushed down to TiFlash
	// If the value is bigger than -1, it will be pushed down to TiFlash, and if the value is 0, it means
	// not limit and spill will never happen
	TiFlashMaxBytesBeforeExternalSort int64

	// TiFlash max query memory per node, -1 and 0 means no limit, and the default value is 0
	// If TiFlashMaxQueryMemoryPerNode > 0 && TiFlashQuerySpillRatio > 0, it will trigger auto spill in TiFlash side, and when auto spill
	// is triggered, per executor's memory usage threshold set by TiFlashMaxBytesBeforeExternalJoin/TiFlashMaxBytesBeforeExternalGroupBy/TiFlashMaxBytesBeforeExternalSort will be ignored.
	TiFlashMaxQueryMemoryPerNode int64

	// TiFlashQuerySpillRatio is the percentage threshold to trigger auto spill in TiFlash if TiFlashMaxQueryMemoryPerNode is set
	TiFlashQuerySpillRatio float64

	// TiDBAllowAutoRandExplicitInsert indicates whether explicit insertion on auto_random column is allowed.
	AllowAutoRandExplicitInsert bool

	// BroadcastJoinThresholdSize is used to limit the size of smaller table.
	// It's unit is bytes, if the size of small table is larger than it, we will not use bcj.
	BroadcastJoinThresholdSize int64

	// BroadcastJoinThresholdCount is used to limit the total count of smaller table.
	// If we can't estimate the size of one side of join child, we will check if its row number exceeds this limitation.
	BroadcastJoinThresholdCount int64

	// PreferBCJByExchangeDataSize indicates the method used to choose mpp broadcast join
	// false: choose mpp broadcast join by `BroadcastJoinThresholdSize` and `BroadcastJoinThresholdCount`
	// true: compare data exchange size of join and choose the smallest one
	PreferBCJByExchangeDataSize bool

	// LimitPushDownThreshold determines if push Limit or TopN down to TiKV forcibly.
	LimitPushDownThreshold int64

	// CorrelationThreshold is the guard to enable row count estimation using column order correlation.
	CorrelationThreshold float64

	// EnableCorrelationAdjustment is used to indicate if correlation adjustment is enabled.
	EnableCorrelationAdjustment bool

	// CorrelationExpFactor is used to control the heuristic approach of row count estimation when CorrelationThreshold is not met.
	CorrelationExpFactor int

	// CopTiFlashConcurrencyFactor is the concurrency number of computation in tiflash coprocessor.
	CopTiFlashConcurrencyFactor float64

	// CurrInsertValues is used to record current ValuesExpr's values.
	// See http://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_values
	CurrInsertValues chunk.Row

	// In https://github.com/pingcap/tidb/issues/14164, we can see that MySQL can enter the column that is not in the insert's SELECT's output.
	// We store the extra columns in this variable.
	CurrInsertBatchExtraCols [][]types.Datum

	// Per-connection time zones. Each client that connects has its own time zone setting, given by the session time_zone variable.
	// See https://dev.mysql.com/doc/refman/5.7/en/time-zone-support.html
	TimeZone *time.Location

	SQLMode mysql.SQLMode

	// AutoIncrementIncrement and AutoIncrementOffset indicates the autoID's start value and increment.
	AutoIncrementIncrement int

	AutoIncrementOffset int

	// SkipASCIICheck check on input value.
	SkipASCIICheck bool

	// SkipUTF8Check check on input value.
	SkipUTF8Check bool

	// DefaultCollationForUTF8MB4 indicates the default collation of UTF8MB4.
	DefaultCollationForUTF8MB4 string

	// BatchInsert indicates if we should split insert data into multiple batches.
	BatchInsert bool

	// BatchDelete indicates if we should split delete data into multiple batches.
	BatchDelete bool

	// BatchCommit indicates if we should split the transaction into multiple batches.
	BatchCommit bool

	// OptimizerSelectivityLevel defines the level of the selectivity estimation in plan.
	OptimizerSelectivityLevel int

	// OptimizerEnableNewOnlyFullGroupByCheck enables the new only_full_group_by check which is implemented by maintaining functional dependency.
	OptimizerEnableNewOnlyFullGroupByCheck bool

	// EnableOuterJoinWithJoinReorder enables TiDB to involve the outer join into the join reorder.
	EnableOuterJoinReorder bool

	// OptimizerEnableNAAJ enables TiDB to use null-aware anti join.
	OptimizerEnableNAAJ bool

	// EnableCascadesPlanner enables the cascades planner.
	EnableCascadesPlanner bool

	// EnableWindowFunction enables the window function.
	EnableWindowFunction bool

	// EnablePipelinedWindowExec enables executing window functions in a pipelined manner.
	EnablePipelinedWindowExec bool

	// AllowProjectionPushDown enables pushdown projection on TiKV.
	AllowProjectionPushDown bool

	// EnableStrictDoubleTypeCheck enables table field double type check.
	EnableStrictDoubleTypeCheck bool

	// EnableVectorizedExpression  enables the vectorized expression evaluation.
	EnableVectorizedExpression bool

	// DDLReorgPriority is the operation priority of adding indices.
	DDLReorgPriority int

	// EnableAutoIncrementInGenerated is used to control whether to allow auto incremented columns in generated columns.
	EnableAutoIncrementInGenerated bool

	// EnablePointGetCache is used to cache value for point get for read only scenario.
	EnablePointGetCache bool

	// PlacementMode the placement mode we use
	//   strict: Check placement settings strictly in ddl operations
	//   ignore: Ignore all placement settings in ddl operations
	PlacementMode string

	// WaitSplitRegionFinish defines the split region behaviour is sync or async.
	WaitSplitRegionFinish bool

	// WaitSplitRegionTimeout defines the split region timeout.
	WaitSplitRegionTimeout uint64

	// EnableChunkRPC indicates whether the coprocessor request can use chunk API.
	EnableChunkRPC bool

	// ConstraintCheckInPlace indicates whether to check the constraint when the SQL executing.
	ConstraintCheckInPlace bool

	// CommandValue indicates which command current session is doing.
	CommandValue uint32

	// TiDBOptJoinReorderThreshold defines the minimal number of join nodes
	// to use the greedy join reorder algorithm.
	TiDBOptJoinReorderThreshold int

	// SlowQueryFile indicates which slow query log file for SLOW_QUERY table to parse.
	SlowQueryFile string

	// EnableFastAnalyze indicates whether to take fast analyze.
	EnableFastAnalyze bool

	// TxnMode indicates should be pessimistic or optimistic.
	TxnMode string

	// MaxExecutionTime is the timeout for select statement, in milliseconds.
	// If the value is 0, timeouts are not enabled.
	// See https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_max_execution_time
	MaxExecutionTime uint64

	// LoadBindingTimeout is the timeout for loading the bind info.
	LoadBindingTimeout uint64

	// TiKVClientReadTimeout is the timeout for readonly kv request in milliseconds, 0 means using default value
	// See https://github.com/pingcap/tidb/blob/7105505a78fc886c33258caa5813baf197b15247/docs/design/2023-06-30-configurable-kv-timeout.md?plain=1#L14-L15
	TiKVClientReadTimeout uint64

	// SQLKiller is a flag to indicate that this query is killed.
	SQLKiller sqlkiller.SQLKiller

	// ConnectionStatus indicates current connection status.
	ConnectionStatus int32

	// ConnectionInfo indicates current connection info used by current session.
	ConnectionInfo *ConnectionInfo

	// NoopFuncsMode allows OFF/ON/WARN values as 0/1/2.
	NoopFuncsMode int

	// StartTime is the start time of the last query. It's set after the query is parsed and before the query is compiled.
	StartTime time.Time

	// DurationParse is the duration of parsing SQL string to AST of the last query.
	DurationParse time.Duration

	// DurationCompile is the duration of compiling AST to execution plan of the last query.
	DurationCompile time.Duration

	// RewritePhaseInfo records all information about the rewriting phase.
	RewritePhaseInfo

	// DurationOptimization is the duration of optimizing a query.
	DurationOptimization time.Duration

	// DurationWaitTS is the duration of waiting for a snapshot TS
	DurationWaitTS time.Duration

	// PrevStmt is used to store the previous executed statement in the current session.
	PrevStmt *LazyStmtText

	// AllowRemoveAutoInc indicates whether a user can drop the auto_increment column attribute or not.
	AllowRemoveAutoInc bool

	// UsePlanBaselines indicates whether we will use plan baselines to adjust plan.
	UsePlanBaselines bool

	// EvolvePlanBaselines indicates whether we will evolve the plan baselines.
	EvolvePlanBaselines bool

	// EnableExtendedStats indicates whether we enable the extended statistics feature.
	EnableExtendedStats bool

	// ReplicaClosestReadThreshold is the minimum response body size that a cop request should be sent to the closest replica.
	// this variable only take effect when `tidb_follower_read` = 'closest-adaptive'
	ReplicaClosestReadThreshold int64

	// IsolationReadEngines is used to isolation read, tidb only read from the stores whose engine type is in the engines.
	IsolationReadEngines map[kv.StoreType]struct{}

	PlannerSelectBlockAsName atomic.Pointer[[]ast.HintTable]

	// LockWaitTimeout is the duration waiting for pessimistic lock in milliseconds
	LockWaitTimeout int64

	// MetricSchemaStep indicates the step when query metric schema.
	MetricSchemaStep int64

	// CDCWriteSource indicates the following data is written by TiCDC if it is not 0.
	CDCWriteSource uint64

	// MetricSchemaRangeDuration indicates the step when query metric schema.
	MetricSchemaRangeDuration int64

	// Some data of cluster-level memory tables will be retrieved many times in different inspection rules,
	// and the cost of retrieving some data is expensive. We use the `TableSnapshot` to cache those data
	// and obtain them lazily, and provide a consistent view of inspection tables for each inspection rules.
	// All cached snapshots will be released at the end of retrieving
	InspectionTableCache map[string]TableSnapshot

	// RowEncoder is reused in session for encode row data.
	RowEncoder rowcodec.Encoder

	// SequenceState cache all sequence's latest value accessed by lastval() builtins. It's a session scoped
	// variable, and all public methods of SequenceState are currently-safe.
	SequenceState *SequenceState

	// WindowingUseHighPrecision determines whether to compute window operations without loss of precision.
	// see https://dev.mysql.com/doc/refman/8.0/en/window-function-optimization.html for more details.
	WindowingUseHighPrecision bool

	// FoundInPlanCache indicates whether this statement was found in plan cache.
	FoundInPlanCache bool
	// PrevFoundInPlanCache indicates whether the last statement was found in plan cache.
	PrevFoundInPlanCache bool

	// FoundInBinding indicates whether the execution plan is matched with the hints in the binding.
	FoundInBinding bool
	// PrevFoundInBinding indicates whether the last execution plan is matched with the hints in the binding.
	PrevFoundInBinding bool

	// OptimizerUseInvisibleIndexes indicates whether optimizer can use invisible index
	OptimizerUseInvisibleIndexes bool

	// SelectLimit limits the max counts of select statement's output
	SelectLimit uint64

	// EnableClusteredIndex indicates whether to enable clustered index when creating a new table.
	EnableClusteredIndex ClusteredIndexDefMode

	// EnableParallelApply indicates that whether to use parallel apply.
	EnableParallelApply bool

	// EnableRedactLog indicates that whether redact log. Possible values are 'OFF', 'ON', 'MARKER'.
	EnableRedactLog string

	// ShardAllocateStep indicates the max size of continuous rowid shard in one transaction.
	ShardAllocateStep int64

	// LastTxnInfo keeps track the info of last committed transaction.
	LastTxnInfo string

	// LastQueryInfo keeps track the info of last query.
	LastQueryInfo sessionstates.QueryInfo

	// LastDDLInfo keeps track the info of last DDL.
	LastDDLInfo sessionstates.LastDDLInfo

	// PartitionPruneMode indicates how and when to prune partitions.
	PartitionPruneMode atomic2.String

	// TxnScope indicates the scope of the transactions. It should be `global` or equal to the value of key `zone` in config.Labels.
	TxnScope kv.TxnScopeVar

	// EnabledRateLimitAction indicates whether enabled ratelimit action during coprocessor
	EnabledRateLimitAction bool

	// EnableAsyncCommit indicates whether to enable the async commit feature.
	EnableAsyncCommit bool

	// Enable1PC indicates whether to enable the one-phase commit feature.
	Enable1PC bool

	// GuaranteeLinearizability indicates whether to guarantee linearizability
	GuaranteeLinearizability bool

	// AnalyzeVersion indicates how TiDB collect and use analyzed statistics.
	AnalyzeVersion int

	// DisableHashJoin indicates whether to disable hash join.
	DisableHashJoin bool

	// UseHashJoinV2 indicates whether to use hash join v2.
	UseHashJoinV2 bool

	// EnableHistoricalStats indicates whether to enable historical statistics.
	EnableHistoricalStats bool

	// EnableIndexMergeJoin indicates whether to enable index merge join.
	EnableIndexMergeJoin bool

	// TrackAggregateMemoryUsage indicates whether to track the memory usage of aggregate function.
	TrackAggregateMemoryUsage bool

	// TiDBEnableExchangePartition indicates whether to enable exchange partition
	TiDBEnableExchangePartition bool

	// AllowFallbackToTiKV indicates the engine types whose unavailability triggers fallback to TiKV.
	// Now we only support TiFlash.
	AllowFallbackToTiKV map[kv.StoreType]struct{}

	// CTEMaxRecursionDepth indicates The common table expression (CTE) maximum recursion depth.
	// see https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_cte_max_recursion_depth
	CTEMaxRecursionDepth int

	// The temporary table size threshold, which is different from MySQL. See https://github.com/pingcap/tidb/issues/28691.
	TMPTableSize int64

	// EnableStableResultMode if stabilize query results.
	EnableStableResultMode bool

	// EnablePseudoForOutdatedStats if using pseudo for outdated stats
	EnablePseudoForOutdatedStats bool

	// RegardNULLAsPoint if regard NULL as Point
	RegardNULLAsPoint bool

	// LocalTemporaryTables is *infoschema.LocalTemporaryTables, use interface to avoid circle dependency.
	// It's nil if there is no local temporary table.
	LocalTemporaryTables any

	// TemporaryTableData stores committed kv values for temporary table for current session.
	TemporaryTableData TemporaryTableData

	// MPPStoreFailTTL indicates the duration that protect TiDB from sending task to a new recovered TiFlash.
	MPPStoreFailTTL string

	// ReadStaleness indicates the staleness duration for the following query
	ReadStaleness time.Duration

	// Rng stores the rand_seed1 and rand_seed2 for Rand() function
	Rng *mathutil.MysqlRng

	// EnablePaging indicates whether enable paging in coprocessor requests.
	EnablePaging bool

	// EnableLegacyInstanceScope says if SET SESSION can be used to set an instance
	// scope variable. The default is TRUE.
	EnableLegacyInstanceScope bool

	// ReadConsistency indicates the read consistency requirement.
	ReadConsistency ReadConsistencyLevel

	// StatsLoadSyncWait indicates how long to wait for stats load before timeout.
	StatsLoadSyncWait atomic.Int64

	// EnableParallelHashaggSpill indicates if parallel hash agg could spill.
	EnableParallelHashaggSpill bool

	// SysdateIsNow indicates whether Sysdate is an alias of Now function
	SysdateIsNow bool
	// EnableMutationChecker indicates whether to check data consistency for mutations
	EnableMutationChecker bool
	// AssertionLevel controls how strict the assertions on data mutations should be.
	AssertionLevel AssertionLevel
	// IgnorePreparedCacheCloseStmt controls if ignore the close-stmt command for prepared statement.
	IgnorePreparedCacheCloseStmt bool
	// EnableNewCostInterface is a internal switch to indicates whether to use the new cost calculation interface.
	EnableNewCostInterface bool
	// CostModelVersion is a internal switch to indicates the Cost Model Version.
	CostModelVersion int
	// IndexJoinDoubleReadPenaltyCostRate indicates whether to add some penalty cost to IndexJoin and how much of it.
	IndexJoinDoubleReadPenaltyCostRate float64

	// BatchPendingTiFlashCount shows the threshold of pending TiFlash tables when batch adding.
	BatchPendingTiFlashCount int
	// RcWriteCheckTS indicates whether some special write statements don't get latest tso from PD at RC
	RcWriteCheckTS bool
	// RemoveOrderbyInSubquery indicates whether to remove ORDER BY in subquery.
	RemoveOrderbyInSubquery bool
	// NonTransactionalIgnoreError indicates whether to ignore error in non-transactional statements.
	// When set to false, returns immediately when it meets the first error.
	NonTransactionalIgnoreError bool

	// MaxAllowedPacket indicates the maximum size of a packet for the MySQL protocol.
	MaxAllowedPacket uint64

	// TiFlash related optimization, only for MPP.
	TiFlashFineGrainedShuffleStreamCount int64
	TiFlashFineGrainedShuffleBatchSize   uint64

	// RequestSourceType is the type of inner request.
	RequestSourceType string
	// ExplicitRequestSourceType is the type of origin external request.
	ExplicitRequestSourceType string

	// MemoryDebugModeMinHeapInUse indicated the minimum heapInUse threshold that triggers the memoryDebugMode.
	MemoryDebugModeMinHeapInUse int64
	// MemoryDebugModeAlarmRatio indicated the allowable bias ratio of memory tracking accuracy check.
	// When `(memory trakced by tidb) * (1+MemoryDebugModeAlarmRatio) < actual heapInUse`, an alarm log will be recorded.
	MemoryDebugModeAlarmRatio int64

	// EnableAnalyzeSnapshot indicates whether to read data on snapshot when collecting statistics.
	// When it is false, ANALYZE reads the latest data.
	// When it is true, ANALYZE reads data on the snapshot at the beginning of ANALYZE.
	EnableAnalyzeSnapshot bool

	// DefaultStrMatchSelectivity adjust the estimation strategy for string matching expressions that can't be estimated by building into range.
	// when > 0: it's the selectivity for the expression.
	// when = 0: try to use TopN to evaluate the like expression to estimate the selectivity.
	DefaultStrMatchSelectivity float64

	// TiFlashFastScan indicates whether use fast scan in TiFlash
	TiFlashFastScan bool

	// PrimaryKeyRequired indicates if sql_require_primary_key sysvar is set
	PrimaryKeyRequired bool

	// EnablePreparedPlanCache indicates whether to enable prepared plan cache.
	EnablePreparedPlanCache bool

	// PreparedPlanCacheSize controls the size of prepared plan cache.
	PreparedPlanCacheSize uint64

	// PreparedPlanCacheMonitor indicates whether to enable prepared plan cache monitor.
	EnablePreparedPlanCacheMemoryMonitor bool

	// EnablePlanCacheForParamLimit controls whether the prepare statement with parameterized limit can be cached
	EnablePlanCacheForParamLimit bool

	// EnablePlanCacheForSubquery controls whether the prepare statement with sub query can be cached
	EnablePlanCacheForSubquery bool

	// EnableNonPreparedPlanCache indicates whether to enable non-prepared plan cache.
	EnableNonPreparedPlanCache bool

	// EnableNonPreparedPlanCacheForDML indicates whether to enable non-prepared plan cache for DML statements.
	EnableNonPreparedPlanCacheForDML bool

	// EnableFuzzyBinding indicates whether to enable fuzzy binding.
	EnableFuzzyBinding bool

	// PlanCacheInvalidationOnFreshStats controls if plan cache will be invalidated automatically when
	// related stats are analyzed after the plan cache is generated.
	PlanCacheInvalidationOnFreshStats bool

	// NonPreparedPlanCacheSize controls the size of non-prepared plan cache.
	NonPreparedPlanCacheSize uint64

	// PlanCacheMaxPlanSize controls the maximum size of a plan that can be cached.
	PlanCacheMaxPlanSize uint64

	// SessionPlanCacheSize controls the size of session plan cache.
	SessionPlanCacheSize uint64

	// ConstraintCheckInPlacePessimistic controls whether to skip the locking of some keys in pessimistic transactions.
	// Postpone the conflict check and constraint check to prewrite or later pessimistic locking requests.
	ConstraintCheckInPlacePessimistic bool

	// EnableTiFlashReadForWriteStmt indicates whether to enable TiFlash to read for write statements.
	EnableTiFlashReadForWriteStmt bool

	// EnableUnsafeSubstitute indicates whether to enable generate column takes unsafe substitute.
	EnableUnsafeSubstitute bool

	// ForeignKeyChecks indicates whether to enable foreign key constraint check.
	ForeignKeyChecks bool

	// RangeMaxSize is the max memory limit for ranges. When the optimizer estimates that the memory usage of complete
	// ranges would exceed the limit, it chooses less accurate ranges such as full range. 0 indicates that there is no
	// memory limit for ranges.
	RangeMaxSize int64

	// LastPlanReplayerToken indicates the last plan replayer token
	LastPlanReplayerToken string

	// InPlanReplayer means we are now executing a statement for a PLAN REPLAYER SQL.
	// Note that PLAN REPLAYER CAPTURE is not included here.
	InPlanReplayer bool

	// AnalyzePartitionConcurrency indicates concurrency for partitions in Analyze
	AnalyzePartitionConcurrency int
	// AnalyzePartitionMergeConcurrency indicates concurrency for merging partition stats
	AnalyzePartitionMergeConcurrency int

	// EnableAsyncMergeGlobalStats indicates whether to enable async merge global stats
	EnableAsyncMergeGlobalStats bool

	// EnableExternalTSRead indicates whether to enable read through external ts
	EnableExternalTSRead bool

	HookContext

	// MemTracker indicates the memory tracker of current session.
	MemTracker *memory.Tracker
	// MemDBDBFootprint tracks the memory footprint of memdb, and is attached to `MemTracker`
	MemDBFootprint *memory.Tracker
	DiskTracker    *memory.Tracker

	// OptPrefixIndexSingleScan indicates whether to do some optimizations to avoid double scan for prefix index.
	// When set to true, `col is (not) null`(`col` is index prefix column) is regarded as index filter rather than table filter.
	OptPrefixIndexSingleScan bool

	// EnableReuseChunk indicates  request chunk whether use chunk alloc
	EnableReuseChunk bool

	// EnableAdvancedJoinHint indicates whether the join method hint is compatible with join order hint.
	EnableAdvancedJoinHint bool

	// EnablePlanReplayerCapture indicates whether enabled plan replayer capture
	EnablePlanReplayerCapture bool

	// EnablePlanReplayedContinuesCapture indicates whether enabled plan replayer continues capture
	EnablePlanReplayedContinuesCapture bool

	// PlanReplayerFinishedTaskKey used to record the finished plan replayer task key in order not to record the
	// duplicate task in plan replayer continues capture
	PlanReplayerFinishedTaskKey map[replayer.PlanReplayerTaskKey]struct{}

	// StoreBatchSize indicates the batch size limit of store batch, set this field to 0 to disable store batch.
	StoreBatchSize int

	// Resource group name
	// NOTE: all statement relate operation should use StmtCtx.ResourceGroupName instead.
	// NOTE: please don't change it directly. Use `SetResourceGroupName`, because it'll need to inc/dec the metrics
	ResourceGroupName string

	// PessimisticTransactionFairLocking controls whether fair locking for pessimistic transaction
	// is enabled.
	PessimisticTransactionFairLocking bool

	// EnableINLJoinInnerMultiPattern indicates whether enable multi pattern for index join inner side
	// For now it is not public to user
	EnableINLJoinInnerMultiPattern bool

	// Enable late materialization: push down some selection condition to tablescan.
	EnableLateMaterialization bool

	// EnableRowLevelChecksum indicates whether row level checksum is enabled.
	EnableRowLevelChecksum bool

	// TiFlashComputeDispatchPolicy indicates how to dipatch task to tiflash_compute nodes.
	// Only for disaggregated-tiflash mode.
	TiFlashComputeDispatchPolicy tiflashcompute.DispatchPolicy

	// SlowTxnThreshold is the threshold of slow transaction logs
	SlowTxnThreshold uint64

	// LoadBasedReplicaReadThreshold is the threshold for the estimated wait duration of a store.
	// If exceeding the threshold, try other stores using replica read.
	LoadBasedReplicaReadThreshold time.Duration

	// OptOrderingIdxSelThresh is the threshold for optimizer to consider the ordering index.
	// If there exists an index whose estimated selectivity is smaller than this threshold, the optimizer won't
	// use the ExpectedCnt to adjust the estimated row count for index scan.
	OptOrderingIdxSelThresh float64

	// OptOrderingIdxSelRatio is the ratio for optimizer to determine when qualified rows from filtering outside
	// of the index will be found during the scan of an ordering index.
	// If all filtering is applied as matching on the ordering index, this ratio will have no impact.
	// Value < 0 disables this enhancement.
	// Value 0 will estimate row(s) found immediately.
	// 0 > value <= 1 applies that percentage as the estimate when rows are found. For example 0.1 = 10%.
	OptOrderingIdxSelRatio float64

	// EnableMPPSharedCTEExecution indicates whether we enable the shared CTE execution strategy on MPP side.
	EnableMPPSharedCTEExecution bool

	// OptimizerFixControl control some details of the optimizer behavior through the tidb_opt_fix_control variable.
	OptimizerFixControl map[uint64]string

	// FastCheckTable is used to control whether fast check table is enabled.
	FastCheckTable bool

	// HypoIndexes are for the Index Advisor.
	HypoIndexes map[string]map[string]map[string]*model.IndexInfo // dbName -> tblName -> idxName -> idxInfo

	// TiFlashReplicaRead indicates the policy of TiFlash node selection when the query needs the TiFlash engine.
	TiFlashReplicaRead tiflash.ReplicaRead

	// HypoTiFlashReplicas are for the Index Advisor.
	HypoTiFlashReplicas map[string]map[string]struct{} // dbName -> tblName -> whether to have replicas

	// Whether to lock duplicate keys in INSERT IGNORE and REPLACE statements,
	// or unchanged unique keys in UPDATE statements, see PR #42210 and #42713
	LockUnchangedKeys bool

	// AnalyzeSkipColumnTypes indicates the column types whose statistics would not be collected when executing the ANALYZE command.
	AnalyzeSkipColumnTypes map[string]struct{}

	// SkipMissingPartitionStats controls how to handle missing partition stats when merging partition stats to global stats.
	// When set to true, skip missing partition stats and continue to merge other partition stats to global stats.
	// When set to false, give up merging partition stats to global stats.
	SkipMissingPartitionStats bool

	// SessionAlias is the identifier of the session
	SessionAlias string

	// OptObjective indicates whether the optimizer should be more stable, predictable or more aggressive.
	// For now, the possible values and corresponding behaviors are:
	// OptObjectiveModerate: The default value. The optimizer considers the real-time stats (real-time row count, modify count).
	// OptObjectiveDeterminate: The optimizer doesn't consider the real-time stats.
	OptObjective string

	CompressionAlgorithm int
	CompressionLevel     int

	// TxnEntrySizeLimit indicates indicates the max size of a entry in membuf. The default limit (from config) will be
	// overwritten if this value is not 0.
	TxnEntrySizeLimit uint64

	// DivPrecisionIncrement indicates the number of digits by which to increase the scale of the result
	// of division operations performed with the / operator.
	DivPrecisionIncrement int

	// allowed when tikv disk full happened.
	DiskFullOpt kvrpcpb.DiskFullOpt

	// GroupConcatMaxLen represents the maximum length of the result of GROUP_CONCAT.
	GroupConcatMaxLen uint64

	// TiFlashPreAggMode indicates the policy of pre aggregation.
	TiFlashPreAggMode string

	// EnableLazyCursorFetch defines whether to enable the lazy cursor fetch.
	EnableLazyCursorFetch bool

	// SharedLockPromotion indicates whether the `select for lock` statements would be executed as the
	// `select for update` statements which do acquire pessimsitic locks.
	SharedLockPromotion bool

	// ScatterRegion will scatter the regions for DDLs when it is "table" or "global", "" indicates not trigger scatter.
	ScatterRegion string

	// CacheStmtExecInfo is a cache for the statement execution information, used to reduce the overhead of memory allocation.
	CacheStmtExecInfo *stmtsummary.StmtExecInfo
	// contains filtered or unexported fields
}

SessionVars is to handle user-defined or global variables in the current session.

func NewSessionVars 

func NewSessionVars(hctx HookContext) *SessionVars

NewSessionVars creates a session vars object.

func (*SessionVars) AddNonPreparedPlanCacheStmt 

func (s *SessionVars) AddNonPreparedPlanCacheStmt(sql string, stmt any)

AddNonPreparedPlanCacheStmt adds this PlanCacheStmt into non-preapred plan-cache stmt cache

func (*SessionVars) AddPlanReplayerFinishedTaskKey 

func (s *SessionVars) AddPlanReplayerFinishedTaskKey(key replayer.PlanReplayerTaskKey)

AddPlanReplayerFinishedTaskKey record finished task key in session

func (*SessionVars) AddPreparedStmt 

func (s *SessionVars) AddPreparedStmt(stmtID uint32, stmt any) error

AddPreparedStmt adds prepareStmt to current session and count in global.

func (*SessionVars) AllocNewPlanID 

func (s *SessionVars) AllocNewPlanID() int

AllocNewPlanID alloc new ID

func (*SessionVars) AllocPlanColumnID 

func (s *SessionVars) AllocPlanColumnID() int64

AllocPlanColumnID allocates column id for plan.

func (*SessionVars) BuildParserConfig 

func (s *SessionVars) BuildParserConfig() parser.ParserConfig

BuildParserConfig generate parser.ParserConfig for initial parser

func (*SessionVars) CheckAndGetTxnScope 

func (s *SessionVars) CheckAndGetTxnScope() string

CheckAndGetTxnScope will return the transaction scope we should use in the current session.

func (*SessionVars) CheckPlanReplayerFinishedTaskKey 

func (s *SessionVars) CheckPlanReplayerFinishedTaskKey(key replayer.PlanReplayerTaskKey) bool

CheckPlanReplayerFinishedTaskKey check whether the key exists

func (*SessionVars) ChooseMppExchangeCompressionMode 

func (s *SessionVars) ChooseMppExchangeCompressionMode() kv.ExchangeCompressionMode

ChooseMppExchangeCompressionMode indicates the data compression method in mpp exchange operator

func (*SessionVars) ChooseMppVersion 

func (s *SessionVars) ChooseMppVersion() kv.MppVersion

ChooseMppVersion indicates the mpp-version used to build mpp plan, if mpp-version is unspecified, use the latest version.

func (*SessionVars) CleanBuffers 

func (s *SessionVars) CleanBuffers()

CleanBuffers cleans the temporary bufs

func (*SessionVars) CleanupTxnReadTSIfUsed 

func (s *SessionVars) CleanupTxnReadTSIfUsed()

CleanupTxnReadTSIfUsed cleans txnReadTS if used

func (*SessionVars) ClearAlloc 

func (s *SessionVars) ClearAlloc(alloc *chunk.Allocator, hasErr bool)

ClearAlloc indicates stop reuse chunk. If `hasErr` is true, it'll also recreate the `alloc` in parameter.

func (*SessionVars) ClearDiskFullOpt 

func (s *SessionVars) ClearDiskFullOpt()

ClearDiskFullOpt resets the session variable DiskFullOpt to DiskFullOpt_NotAllowedOnFull.

func (*SessionVars) ClearRelatedTableForMDL 

func (s *SessionVars) ClearRelatedTableForMDL()

ClearRelatedTableForMDL clears the related table for MDL. related tables for MDL is filled during build logical plan or Preprocess for all DataSources, even for queries inside DDLs like `create view as select xxx` and `create table as select xxx`. it should be cleared before we execute the DDL statement.

func (*SessionVars) DecodeSessionStates 

func (s *SessionVars) DecodeSessionStates(_ context.Context, sessionStates *sessionstates.SessionStates) (err error)

DecodeSessionStates restores session states from SessionStates.

func (*SessionVars) EnableEvalTopNEstimationForStrMatch 

func (s *SessionVars) EnableEvalTopNEstimationForStrMatch() bool

EnableEvalTopNEstimationForStrMatch means if we need to evaluate expression with TopN to improve estimation. Currently, it's only for string matching functions (like and regexp).

func (*SessionVars) EnableForceInlineCTE 

func (s *SessionVars) EnableForceInlineCTE() bool

EnableForceInlineCTE returns the session variable enableForceInlineCTE

func (*SessionVars) EncodeSessionStates 

func (s *SessionVars) EncodeSessionStates(_ context.Context, sessionStates *sessionstates.SessionStates) (err error)

EncodeSessionStates saves session states into SessionStates.

func (*SessionVars) ExchangeChunkStatus 

func (s *SessionVars) ExchangeChunkStatus()

ExchangeChunkStatus give the status to preUseChunkAlloc

func (*SessionVars) GetAllowInSubqToJoinAndAgg 

func (s *SessionVars) GetAllowInSubqToJoinAndAgg() bool

GetAllowInSubqToJoinAndAgg get AllowInSubqToJoinAndAgg from sql hints and SessionVars.allowInSubqToJoinAndAgg.

func (*SessionVars) GetAllowPreferRangeScan 

func (s *SessionVars) GetAllowPreferRangeScan() bool

GetAllowPreferRangeScan get preferRangeScan from SessionVars.preferRangeScan.

func (*SessionVars) GetCPUFactor 

func (s *SessionVars) GetCPUFactor() float64

GetCPUFactor returns the session variable cpuFactor

func (*SessionVars) GetCharsetInfo 

func (s *SessionVars) GetCharsetInfo() (charset, collation string)

GetCharsetInfo gets charset and collation for current context. What character set should the server translate a statement to after receiving it? For this, the server uses the character_set_connection and collation_connection system variables. It converts statements sent by the client from character_set_client to character_set_connection (except for string literals that have an introducer such as _latin1 or _utf8). collation_connection is important for comparisons of literal strings. For comparisons of strings with column values, collation_connection does not matter because columns have their own collation, which has a higher collation precedence. See https://dev.mysql.com/doc/refman/5.7/en/charset-connection.html

func (*SessionVars) GetChunkAllocator 

func (s *SessionVars) GetChunkAllocator() chunk.Allocator

GetChunkAllocator returns a valid chunk allocator.

func (*SessionVars) GetConcurrencyFactor 

func (s *SessionVars) GetConcurrencyFactor() float64

GetConcurrencyFactor returns the session variable concurrencyFactor

func (*SessionVars) GetCopCPUFactor 

func (s *SessionVars) GetCopCPUFactor() float64

GetCopCPUFactor returns the session variable copCPUFactor

func (*SessionVars) GetDescScanFactor 

func (s *SessionVars) GetDescScanFactor(tbl *model.TableInfo) float64

GetDescScanFactor returns the session variable descScanFactor returns 0 when tbl is a temporary table.

func (*SessionVars) GetDiskFactor 

func (s *SessionVars) GetDiskFactor() float64

GetDiskFactor returns the session variable diskFactor

func (*SessionVars) GetDiskFullOpt 

func (s *SessionVars) GetDiskFullOpt() kvrpcpb.DiskFullOpt

GetDiskFullOpt returns the value of DiskFullOpt in the current session.

func (*SessionVars) GetDivPrecisionIncrement 

func (s *SessionVars) GetDivPrecisionIncrement() int

GetDivPrecisionIncrement returns the specified value of DivPrecisionIncrement.

func (*SessionVars) GetEnableCascadesPlanner 

func (s *SessionVars) GetEnableCascadesPlanner() bool

GetEnableCascadesPlanner get EnableCascadesPlanner from sql hints and SessionVars.EnableCascadesPlanner.

func (*SessionVars) GetEnableIndexMerge 

func (s *SessionVars) GetEnableIndexMerge() bool

GetEnableIndexMerge get EnableIndexMerge from SessionVars.enableIndexMerge.

func (*SessionVars) GetEnablePseudoForOutdatedStats 

func (s *SessionVars) GetEnablePseudoForOutdatedStats() bool

GetEnablePseudoForOutdatedStats get EnablePseudoForOutdatedStats from SessionVars.EnablePseudoForOutdatedStats.

func (*SessionVars) GetExecuteDuration 

func (s *SessionVars) GetExecuteDuration() time.Duration

GetExecuteDuration returns the execute duration of the last statement in the current session.

func (*SessionVars) GetGlobalSystemVar 

func (s *SessionVars) GetGlobalSystemVar(ctx context.Context, name string) (string, error)

GetGlobalSystemVar gets a global system variable.

func (*SessionVars) GetIsolationReadEngines 

func (s *SessionVars) GetIsolationReadEngines() map[kv.StoreType]struct{}

GetIsolationReadEngines gets isolation read engines.

func (*SessionVars) GetMaxExecutionTime 

func (s *SessionVars) GetMaxExecutionTime() uint64

GetMaxExecutionTime get the max execution timeout value.

func (*SessionVars) GetMemoryFactor 

func (s *SessionVars) GetMemoryFactor() float64

GetMemoryFactor returns the session variable memoryFactor

func (*SessionVars) GetNegateStrMatchDefaultSelectivity 

func (s *SessionVars) GetNegateStrMatchDefaultSelectivity() float64

GetNegateStrMatchDefaultSelectivity means the default selectivity for not like and not regexp. Note: 

  0 is a special value, which means the default selectivity is 0.9 and TopN assisted estimation is enabled.
  0.8 (the default value) is also a special value. For backward compatibility, when the variable is set to 0.8, we
keep the default selectivity of like/regexp and not like/regexp all 0.8.

func (*SessionVars) GetNetworkFactor 

func (s *SessionVars) GetNetworkFactor(tbl *model.TableInfo) float64

GetNetworkFactor returns the session variable networkFactor returns 0 when tbl is a temporary table.

func (*SessionVars) GetNextPreparedStmtID 

func (s *SessionVars) GetNextPreparedStmtID() uint32

GetNextPreparedStmtID generates and returns the next session scope prepared statement id.

func (*SessionVars) GetNonPreparedPlanCacheStmt 

func (s *SessionVars) GetNonPreparedPlanCacheStmt(sql string) any

GetNonPreparedPlanCacheStmt gets the PlanCacheStmt.

func (*SessionVars) GetOptObjective 

func (s *SessionVars) GetOptObjective() string

GetOptObjective return the session variable "tidb_opt_objective". Please see comments of SessionVars.OptObjective for details.

func (*SessionVars) GetOptimizerFixControlMap 

func (s *SessionVars) GetOptimizerFixControlMap() map[uint64]string

GetOptimizerFixControlMap returns the specified value of the optimizer fix control.

func (*SessionVars) GetParseParams 

func (s *SessionVars) GetParseParams() []parser.ParseParam

GetParseParams gets the parse parameters from session variables.

func (*SessionVars) GetPreparedStmtByID 

func (s *SessionVars) GetPreparedStmtByID(stmtID uint32) (any, error)

GetPreparedStmtByID returns the prepared statement specified by stmtID.

func (*SessionVars) GetPreparedStmtByName 

func (s *SessionVars) GetPreparedStmtByName(stmtName string) (any, error)

GetPreparedStmtByName returns the prepared statement specified by stmtName.

func (*SessionVars) GetPrevStmtDigest 

func (s *SessionVars) GetPrevStmtDigest() string

GetPrevStmtDigest returns the digest of the previous statement.

func (*SessionVars) GetReadableTxnMode 

func (s *SessionVars) GetReadableTxnMode() string

GetReadableTxnMode returns the session variable TxnMode but rewrites it to "OPTIMISTIC" when it's empty.

func (*SessionVars) GetRelatedTableForMDL 

func (s *SessionVars) GetRelatedTableForMDL() *sync.Map

GetRelatedTableForMDL gets the related table for metadata lock.

func (*SessionVars) GetReplicaRead 

func (s *SessionVars) GetReplicaRead() kv.ReplicaReadType

GetReplicaRead get ReplicaRead from sql hints and SessionVars.replicaRead.

func (*SessionVars) GetRowIDShardGenerator 

func (s *SessionVars) GetRowIDShardGenerator() *RowIDShardGenerator

GetRowIDShardGenerator shard row id generator

func (*SessionVars) GetRuntimeFilterMode 

func (s *SessionVars) GetRuntimeFilterMode() RuntimeFilterMode

GetRuntimeFilterMode return the session variable runtimeFilterMode

func (*SessionVars) GetRuntimeFilterTypes 

func (s *SessionVars) GetRuntimeFilterTypes() []RuntimeFilterType

GetRuntimeFilterTypes return the session variable runtimeFilterTypes

func (*SessionVars) GetScanFactor 

func (s *SessionVars) GetScanFactor(tbl *model.TableInfo) float64

GetScanFactor returns the session variable scanFactor returns 0 when tbl is a temporary table.

func (*SessionVars) GetSeekFactor 

func (s *SessionVars) GetSeekFactor(tbl *model.TableInfo) float64

GetSeekFactor returns the session variable seekFactor returns 0 when tbl is a temporary table.

func (*SessionVars) GetSessionOrGlobalSystemVar 

func (s *SessionVars) GetSessionOrGlobalSystemVar(ctx context.Context, name string) (string, error)

GetSessionOrGlobalSystemVar gets a system variable. If it is a session only variable, use the default value defined in code. Returns error if there is no such variable.

func (*SessionVars) GetSessionStatesSystemVar 

func (s *SessionVars) GetSessionStatesSystemVar(name string) (string, bool, error)

GetSessionStatesSystemVar gets the session variable value for session states. It's only used for encoding session states when migrating a session. The returned boolean indicates whether to keep this value in the session states.

func (*SessionVars) GetSessionVars 

func (s *SessionVars) GetSessionVars() *SessionVars

GetSessionVars implements the `SessionVarsProvider` interface.

func (*SessionVars) GetSplitRegionTimeout 

func (s *SessionVars) GetSplitRegionTimeout() time.Duration

GetSplitRegionTimeout gets split region timeout.

func (*SessionVars) GetStrMatchDefaultSelectivity 

func (s *SessionVars) GetStrMatchDefaultSelectivity() float64

GetStrMatchDefaultSelectivity means the default selectivity for like and regexp. Note: 0 is a special value, which means the default selectivity is 0.1 and TopN assisted estimation is enabled.

func (*SessionVars) GetSystemVar 

func (s *SessionVars) GetSystemVar(name string) (string, bool)

GetSystemVar gets the string value of a system variable.

func (*SessionVars) GetTemporaryTable 

func (s *SessionVars) GetTemporaryTable(tblInfo *model.TableInfo) tableutil.TempTable

GetTemporaryTable returns a TempTable by tableInfo.

func (*SessionVars) GetTiKVClientReadTimeout 

func (s *SessionVars) GetTiKVClientReadTimeout() uint64

GetTiKVClientReadTimeout returns readonly kv request timeout, prefer query hint over session variable

func (*SessionVars) GetTotalCostDuration 

func (s *SessionVars) GetTotalCostDuration() time.Duration

GetTotalCostDuration returns the total cost duration of the last statement in the current session.

func (*SessionVars) GetUseChunkAlloc 

func (s *SessionVars) GetUseChunkAlloc() bool

GetUseChunkAlloc return useChunkAlloc status

func (*SessionVars) GetWriteStmtBufs 

func (s *SessionVars) GetWriteStmtBufs() *WriteStmtBufs

GetWriteStmtBufs get pointer of SessionVars.writeStmtBufs.

func (*SessionVars) HasStatusFlag 

func (s *SessionVars) HasStatusFlag(flag uint16) bool

HasStatusFlag gets the session server status variable, returns true if it is on.

func (*SessionVars) InTxn 

func (s *SessionVars) InTxn() bool

InTxn returns if the session is in transaction.

func (*SessionVars) InitStatementContext 

func (s *SessionVars) InitStatementContext() *stmtctx.StatementContext

InitStatementContext initializes a StatementContext, the object is reused to reduce allocation.

func (*SessionVars) IsAllocValid 

func (s *SessionVars) IsAllocValid() bool

IsAllocValid check if chunk reuse is enable or chunkPool is inused.

func (*SessionVars) IsAutocommit 

func (s *SessionVars) IsAutocommit() bool

IsAutocommit returns if the session is set to autocommit.

func (*SessionVars) IsDynamicPartitionPruneEnabled 

func (s *SessionVars) IsDynamicPartitionPruneEnabled() bool

IsDynamicPartitionPruneEnabled indicates whether dynamic partition prune enabled Note that: IsDynamicPartitionPruneEnabled only indicates whether dynamic partition prune mode is enabled according to session variable, it isn't guaranteed to be used during query due to other conditions checking.

func (*SessionVars) IsIsolation 

func (s *SessionVars) IsIsolation(isolation string) bool

IsIsolation if true it means the transaction is at that isolation level.

func (*SessionVars) IsMPPAllowed 

func (s *SessionVars) IsMPPAllowed() bool

IsMPPAllowed returns whether mpp execution is allowed.

func (*SessionVars) IsMPPEnforced 

func (s *SessionVars) IsMPPEnforced() bool

IsMPPEnforced returns whether mpp execution is enforced.

func (*SessionVars) IsPessimisticReadConsistency 

func (s *SessionVars) IsPessimisticReadConsistency() bool

IsPessimisticReadConsistency if true it means the statement is in a read consistency pessimistic transaction.

func (*SessionVars) IsPlanReplayerCaptureEnabled 

func (s *SessionVars) IsPlanReplayerCaptureEnabled() bool

IsPlanReplayerCaptureEnabled indicates whether capture or continues capture enabled

func (*SessionVars) IsReplicaReadClosestAdaptive 

func (s *SessionVars) IsReplicaReadClosestAdaptive() bool

IsReplicaReadClosestAdaptive returns whether adaptive closest replica can be enabled.

func (*SessionVars) IsRowLevelChecksumEnabled 

func (s *SessionVars) IsRowLevelChecksumEnabled() bool

IsRowLevelChecksumEnabled indicates whether row level checksum is enabled for current session, that is tidb_enable_row_level_checksum is on and tidb_row_format_version is 2 and it's not a internal session.

func (*SessionVars) IsRuntimeFilterEnabled 

func (s *SessionVars) IsRuntimeFilterEnabled() bool

IsRuntimeFilterEnabled return runtime filter mode whether OFF

func (*SessionVars) IsTiFlashCopBanned 

func (s *SessionVars) IsTiFlashCopBanned() bool

IsTiFlashCopBanned returns whether cop execution is allowed.

func (*SessionVars) IsolationLevelForNewTxn 

func (s *SessionVars) IsolationLevelForNewTxn() (isolation string)

IsolationLevelForNewTxn returns the isolation level if we want to enter a new transaction

func (*SessionVars) Location 

func (s *SessionVars) Location() *time.Location

Location returns the value of time_zone session variable. If it is nil, then return time.Local.

func (*SessionVars) PessimisticLockEligible 

func (s *SessionVars) PessimisticLockEligible() bool

PessimisticLockEligible indicates whether pessimistic lock should not be ignored for the current statement execution. There are cases the `for update` clause should not take effect, like autocommit statements with “pessimistic-auto-commit disabled.

func (*SessionVars) RaiseWarningWhenMPPEnforced 

func (s *SessionVars) RaiseWarningWhenMPPEnforced(warning string)

RaiseWarningWhenMPPEnforced will raise a warning when mpp mode is enforced and executing explain statement. TODO: Confirm whether this function will be inlined and omit the overhead of string construction when calling with false condition.

func (*SessionVars) RegisterScalarSubQ 

func (s *SessionVars) RegisterScalarSubQ(scalarSubQ any)

RegisterScalarSubQ register a scalar sub query into the map. This will be used for EXPLAIN.

func (*SessionVars) RemovePreparedStmt 

func (s *SessionVars) RemovePreparedStmt(stmtID uint32)

RemovePreparedStmt removes preparedStmt from current session and decrease count in global.

func (*SessionVars) SetAlloc 

func (s *SessionVars) SetAlloc(alloc chunk.Allocator)

SetAlloc Attempt to set the buffer pool address

func (*SessionVars) SetAllowInSubqToJoinAndAgg 

func (s *SessionVars) SetAllowInSubqToJoinAndAgg(val bool)

SetAllowInSubqToJoinAndAgg set SessionVars.allowInSubqToJoinAndAgg.

func (*SessionVars) SetAllowPreferRangeScan 

func (s *SessionVars) SetAllowPreferRangeScan(val bool)

SetAllowPreferRangeScan set SessionVars.preferRangeScan.

func (*SessionVars) SetDiskFullOpt 

func (s *SessionVars) SetDiskFullOpt(level kvrpcpb.DiskFullOpt)

SetDiskFullOpt sets the session variable DiskFullOpt

func (*SessionVars) SetEnableCascadesPlanner 

func (s *SessionVars) SetEnableCascadesPlanner(val bool)

SetEnableCascadesPlanner set SessionVars.EnableCascadesPlanner.

func (*SessionVars) SetEnableIndexMerge 

func (s *SessionVars) SetEnableIndexMerge(val bool)

SetEnableIndexMerge set SessionVars.enableIndexMerge.

func (*SessionVars) SetEnablePseudoForOutdatedStats 

func (s *SessionVars) SetEnablePseudoForOutdatedStats(val bool)

SetEnablePseudoForOutdatedStats set SessionVars.EnablePseudoForOutdatedStats.

func (*SessionVars) SetInTxn 

func (s *SessionVars) SetInTxn(val bool)

SetInTxn sets whether the session is in transaction. It also updates the IsExplicit flag in TxnCtx if val is true.

func (*SessionVars) SetLastInsertID 

func (s *SessionVars) SetLastInsertID(insertID uint64)

SetLastInsertID saves the last insert id to the session context. TODO: we may store the result for last_insert_id sys var later.

func (*SessionVars) SetNextPreparedStmtID 

func (s *SessionVars) SetNextPreparedStmtID(preparedStmtID uint32)

SetNextPreparedStmtID sets the next prepared statement id. It's only used in restoring session states.

func (*SessionVars) SetPrevStmtDigest 

func (s *SessionVars) SetPrevStmtDigest(prevStmtDigest string)

SetPrevStmtDigest sets the digest of the previous statement.

func (*SessionVars) SetReplicaRead 

func (s *SessionVars) SetReplicaRead(val kv.ReplicaReadType)

SetReplicaRead set SessionVars.replicaRead.

func (*SessionVars) SetResourceGroupName 

func (s *SessionVars) SetResourceGroupName(groupName string)

SetResourceGroupName changes the resource group name and inc/dec the metrics accordingly.

func (*SessionVars) SetStatusFlag 

func (s *SessionVars) SetStatusFlag(flag uint16, on bool)

SetStatusFlag sets the session server status variable. If on is true sets the flag in session status, otherwise removes the flag.

func (*SessionVars) SetStringUserVar 

func (s *SessionVars) SetStringUserVar(name string, strVal string, collation string)

SetStringUserVar set the value and collation for user defined variable.

func (*SessionVars) SetSystemVar 

func (s *SessionVars) SetSystemVar(name string, val string) error

SetSystemVar sets the value of a system variable for session scope. Values are automatically normalized (i.e. oN / on / 1 => ON) and the validation function is run. To set with less validation, see SetSystemVarWithRelaxedValidation.

func (*SessionVars) SetSystemVarWithOldValAsRet 

func (s *SessionVars) SetSystemVarWithOldValAsRet(name string, val string) (string, error)

SetSystemVarWithOldValAsRet is wrapper of SetSystemVar. Return the old value for later use.

func (*SessionVars) SetSystemVarWithRelaxedValidation 

func (s *SessionVars) SetSystemVarWithRelaxedValidation(name string, val string) error

SetSystemVarWithRelaxedValidation sets the value of a system variable for session scope. Validation functions are called, but scope validation is skipped. Errors are not expected to be returned because this could cause upgrade issues.

func (*SessionVars) SetSystemVarWithoutValidation 

func (s *SessionVars) SetSystemVarWithoutValidation(name string, val string) error

SetSystemVarWithoutValidation sets the value of a system variable for session scope. Deprecated: Values are NOT normalized or Validated.

func (*SessionVars) SetTxnIsolationLevelOneShotStateForNextTxn 

func (s *SessionVars) SetTxnIsolationLevelOneShotStateForNextTxn()

SetTxnIsolationLevelOneShotStateForNextTxn sets the txnIsolationLevelOneShot.state for next transaction.

func (*SessionVars) SlowLogFormat 

func (s *SessionVars) SlowLogFormat(logItems *SlowQueryLogItems) string

SlowLogFormat uses for formatting slow log. The slow log output is like below: # Time: 2019-04-28T15:24:04.309074+08:00 # Txn_start_ts: 406315658548871171 # Keyspace_name: keyspace_a # Keyspace_ID: 1 # User@Host: root[root] @ localhost [127.0.0.1] # Conn_ID: 6 # Query_time: 4.895492 # Process_time: 0.161 Request_count: 1 Total_keys: 100001 Processed_keys: 100000 # DB: test # Index_names: [t1.idx1,t2.idx2] # Is_internal: false # Digest: 42a1c8aae6f133e934d4bf0147491709a8812ea05ff8819ec522780fe657b772 # Stats: t1:1,t2:2 # Num_cop_tasks: 10 # Cop_process: Avg_time: 1s P90_time: 2s Max_time: 3s Max_addr: 10.6.131.78 # Cop_wait: Avg_time: 10ms P90_time: 20ms Max_time: 30ms Max_Addr: 10.6.131.79 # Memory_max: 4096 # Disk_max: 65535 # Succ: true # Prev_stmt: begin; select * from t_slim;

func (*SessionVars) Status 

func (s *SessionVars) Status() uint16

Status returns the server status.

func (*SessionVars) UseLowResolutionTSO 

func (s *SessionVars) UseLowResolutionTSO() bool

UseLowResolutionTSO indicates whether low resolution tso could be used for execution. After `tidb_low_resolution_tso` supports the global scope, this variable is expected to only affect user sessions and not impact internal background sessions and tasks. Currently, one of the problems is that the determination of whether a session is an internal task session within TiDB is quite inconsistent and chaotic, posing risks. Some internal sessions rely on upper-level users correctly using `ExecuteInternal` or `ExecuteRestrictedSQL` for assurance. Additionally, the BR code also contains some session-related encapsulation and usage.

TODO: There needs to be a more comprehensive and unified entry point to ensure that all internal sessions and global user sessions/variables are isolated and do not affect each other.

func (*SessionVars) WithdrawAllPreparedStmt 

func (s *SessionVars) WithdrawAllPreparedStmt()

WithdrawAllPreparedStmt remove all preparedStmt in current session and decrease count in global.

type SessionVarsProvider 

type SessionVarsProvider interface {
	GetSessionVars() *SessionVars
}

SessionVarsProvider provides the session variables.

type SlowQueryLogItems 

type SlowQueryLogItems struct {
	TxnTS             uint64
	KeyspaceName      string
	KeyspaceID        uint32
	SQL               string
	Digest            string
	TimeTotal         time.Duration
	TimeParse         time.Duration
	TimeCompile       time.Duration
	TimeOptimize      time.Duration
	TimeWaitTS        time.Duration
	IndexNames        string
	CopTasks          *execdetails.CopTasksDetails
	ExecDetail        execdetails.ExecDetails
	MemMax            int64
	DiskMax           int64
	Succ              bool
	Prepared          bool
	PlanFromCache     bool
	PlanFromBinding   bool
	HasMoreResults    bool
	PrevStmt          string
	Plan              string
	PlanDigest        string
	BinaryPlan        string
	RewriteInfo       RewritePhaseInfo
	KVTotal           time.Duration
	PDTotal           time.Duration
	BackoffTotal      time.Duration
	WriteSQLRespTotal time.Duration
	ExecRetryCount    uint
	ExecRetryTime     time.Duration
	ResultRows        int64
	IsExplicitTxn     bool
	IsWriteCacheTable bool
	UsedStats         *stmtctx.UsedStatsInfo
	IsSyncStatsFailed bool
	Warnings          []JSONSQLWarnForSlowLog
	ResourceGroupName string
	RRU               float64
	WRU               float64
	WaitRUDuration    time.Duration
	CPUUsages         ppcpuusage.CPUUsages
}

SlowQueryLogItems is a collection of items that should be included in the slow query log.

type Statistics 

type Statistics interface {
	// GetScope gets the status variables scope.
	GetScope(status string) ScopeFlag
	// Stats returns the statistics status variables.
	Stats(*SessionVars) (map[string]any, error)
}

Statistics is the interface of statistics.

type StatusVal 

type StatusVal struct {
	Scope ScopeFlag
	Value any
}

StatusVal is the value of the corresponding status variable.

type SysVar 

type SysVar struct {
	// Scope is for whether can be changed or not
	Scope ScopeFlag
	// Name is the variable name.
	Name string
	// Value is the variable value.
	Value string
	// Type is the MySQL type (optional)
	Type TypeFlag
	// MinValue will automatically be validated when specified (optional)
	MinValue int64
	// MaxValue will automatically be validated when specified (optional)
	MaxValue uint64
	// AutoConvertNegativeBool applies to boolean types (optional)
	AutoConvertNegativeBool bool
	// ReadOnly applies to all types
	ReadOnly bool
	// PossibleValues applies to ENUM type
	PossibleValues []string
	// AllowEmpty is a special TiDB behavior which means "read value from config" (do not use)
	AllowEmpty bool
	// AllowEmptyAll is a special behavior that only applies to TiDBCapturePlanBaseline, TiDBTxnMode (do not use)
	AllowEmptyAll bool
	// AllowAutoValue means that the special value "-1" is permitted, even when outside of range.
	AllowAutoValue bool
	// Validation is a callback after the type validation has been performed, but before the Set function
	Validation func(*SessionVars, string, string, ScopeFlag) (string, error)
	// SetSession is called after validation but before updating systems[]. It also doubles as an Init function
	// and will be called on all variables in builtinGlobalVariable, regardless of their scope.
	SetSession func(*SessionVars, string) error
	// SetGlobal is called after validation
	SetGlobal func(context.Context, *SessionVars, string) error
	// IsHintUpdatableVerified indicate whether we've confirmed that SET_VAR() hint is worked for this hint.
	IsHintUpdatableVerified bool
	// Deprecated: Hidden previously meant that the variable still responds to SET but doesn't show up in SHOW VARIABLES
	// However, this feature is no longer used. All variables are visible.
	Hidden bool
	// Aliases is a list of sysvars that should also be updated when this sysvar is updated.
	// Updating aliases calls the SET function of the aliases, but does not update their aliases (preventing SET recursion)
	Aliases []string
	// GetSession is a getter function for session scope.
	// It can be used by instance-scoped variables to overwrite the previously expected value.
	GetSession func(*SessionVars) (string, error)
	// GetGlobal is a getter function for global scope.
	GetGlobal func(context.Context, *SessionVars) (string, error)
	// GetStateValue gets the value for session states, which is used for migrating sessions.
	// We need a function to override GetSession sometimes, because GetSession may not return the real value.
	GetStateValue func(*SessionVars) (string, bool, error)
	// Depended indicates whether other variables depend on this one. That is, if this one is not correctly set,
	// another variable cannot be set either.
	// This flag is used to decide the order to replay session variables.
	Depended bool

	// IsNoop defines if the sysvar is a noop included for MySQL compatibility
	IsNoop bool
	// GlobalConfigName is the global config name of this global variable.
	// If the global variable has the global config name,
	// it should store the global config into PD(etcd) too when set global variable.
	GlobalConfigName string
	// RequireDynamicPrivileges is a function to return a dynamic privilege list to check the set sysvar privilege
	RequireDynamicPrivileges func(isGlobal bool, sem bool) []string
	// contains filtered or unexported fields
}

SysVar is for system variable. All the fields of SysVar should be READ ONLY after created.

func GetSysVar 

func GetSysVar(name string) *SysVar

GetSysVar returns sys var info for name as key.

func (*SysVar) GetGlobalFromHook 

func (sv *SysVar) GetGlobalFromHook(ctx context.Context, s *SessionVars) (string, error)

GetGlobalFromHook calls the GetSession func if it exists.

func (*SysVar) GetNativeValType 

func (sv *SysVar) GetNativeValType(val string) (types.Datum, byte, uint)

GetNativeValType attempts to convert the val to the approx MySQL non-string type TODO: only return 3 types now, support others like DOUBLE, TIME later

func (*SysVar) GetSessionFromHook 

func (sv *SysVar) GetSessionFromHook(s *SessionVars) (string, error)

GetSessionFromHook calls the GetSession func if it exists.

func (*SysVar) HasGlobalScope 

func (sv *SysVar) HasGlobalScope() bool

HasGlobalScope returns true if the scope for the sysVar includes global.

func (*SysVar) HasInstanceScope 

func (sv *SysVar) HasInstanceScope() bool

HasInstanceScope returns true if the scope for the sysVar includes instance

func (*SysVar) HasNoneScope 

func (sv *SysVar) HasNoneScope() bool

HasNoneScope returns true if the scope for the sysVar is None.

func (*SysVar) HasSessionScope 

func (sv *SysVar) HasSessionScope() bool

HasSessionScope returns true if the scope for the sysVar includes session.

func (*SysVar) SetGlobalFromHook 

func (sv *SysVar) SetGlobalFromHook(ctx context.Context, s *SessionVars, val string, skipAliases bool) error

SetGlobalFromHook calls the SetGlobal func if it exists.

func (*SysVar) SetSessionFromHook 

func (sv *SysVar) SetSessionFromHook(s *SessionVars, val string) error

SetSessionFromHook calls the SetSession func if it exists.

func (*SysVar) SkipInit 

func (sv *SysVar) SkipInit() bool

SkipInit returns true if when a new session is created we should "skip" copying an initial value to it (and call the SetSession func if it exists)

func (*SysVar) SkipSysvarCache 

func (sv *SysVar) SkipSysvarCache() bool

SkipSysvarCache returns true if the sysvar should not re-execute on peers This doesn't make sense for the GC variables because they are based in tikv tables. We'd effectively be reading and writing to the same table, which could be in an unsafe manner. In future these variables might be converted to not use a different table internally, but to do that we need to first fix upgrade/downgrade so we know that older servers won't be in the cluster which update only these values.

func (*SysVar) Validate 

func (sv *SysVar) Validate(vars *SessionVars, value string, scope ScopeFlag) (string, error)

Validate checks if system variable satisfies specific restriction.

func (*SysVar) ValidateFromType 

func (sv *SysVar) ValidateFromType(vars *SessionVars, value string, scope ScopeFlag) (string, error)

ValidateFromType provides automatic validation based on the SysVar's type

func (*SysVar) ValidateWithRelaxedValidation 

func (sv *SysVar) ValidateWithRelaxedValidation(vars *SessionVars, value string, scope ScopeFlag) string

ValidateWithRelaxedValidation normalizes values but can not return errors. Normalization+validation needs to be applied when reading values because older versions of TiDB may be less sophisticated in normalizing values. But errors should be caught and handled, because otherwise there will be upgrade issues.

type TableDelta 

type TableDelta struct {
	Delta    int64
	Count    int64
	ColSize  map[int64]int64
	InitTime time.Time // InitTime is the time that this delta is generated.
	TableID  int64
}

TableDelta stands for the changed count for one table or partition.

func (TableDelta) Clone 

func (td TableDelta) Clone() TableDelta

Clone returns a cloned TableDelta.

type TableSnapshot 

type TableSnapshot struct {
	Rows [][]types.Datum
	Err  error
}

TableSnapshot represents a data snapshot of the table contained in `information_schema`.

type TemporaryTableData 

type TemporaryTableData interface {
	kv.Retriever
	// Staging create a new staging buffer inside the MemBuffer.
	// Subsequent writes will be temporarily stored in this new staging buffer.
	// When you think all modifications looks good, you can call `Release` to public all of them to the upper level buffer.
	Staging() kv.StagingHandle
	// Release publish all modifications in the latest staging buffer to upper level.
	Release(kv.StagingHandle)
	// Cleanup cleanups the resources referenced by the StagingHandle.
	// If the changes are not published by `Release`, they will be discarded.
	Cleanup(kv.StagingHandle)
	// GetTableSize get the size of a table
	GetTableSize(tblID int64) int64
	// DeleteTableKey removes the entry for key k from table
	DeleteTableKey(tblID int64, k kv.Key) error
	// SetTableKey sets the entry for k from table
	SetTableKey(tblID int64, k kv.Key, val []byte) error
}

TemporaryTableData is a interface to maintain temporary data in session

func NewTemporaryTableData 

func NewTemporaryTableData(memBuffer kv.MemBuffer) TemporaryTableData

NewTemporaryTableData creates a new TemporaryTableData

type TransactionContext 

type TransactionContext struct {
	TxnCtxNoNeedToRestore
	TxnCtxNeedToRestore
}

TransactionContext is used to store variables that has transaction scope.

func (*TransactionContext) AddSavepoint 

func (tc *TransactionContext) AddSavepoint(name string, memdbCheckpoint *tikv.MemDBCheckpoint)

AddSavepoint adds a new savepoint.

func (*TransactionContext) AddUnchangedKeyForLock 

func (tc *TransactionContext) AddUnchangedKeyForLock(key []byte)

AddUnchangedKeyForLock adds an unchanged key for pessimistic lock.

func (*TransactionContext) Cleanup 

func (tc *TransactionContext) Cleanup()

Cleanup clears up transaction info that no longer use.

func (*TransactionContext) ClearDelta 

func (tc *TransactionContext) ClearDelta()

ClearDelta clears the delta map.

func (*TransactionContext) CollectUnchangedKeysForLock 

func (tc *TransactionContext) CollectUnchangedKeysForLock(buf []kv.Key) []kv.Key

CollectUnchangedKeysForLock collects unchanged keys for pessimistic lock.

func (*TransactionContext) DeleteSavepoint 

func (tc *TransactionContext) DeleteSavepoint(name string) bool

DeleteSavepoint deletes the savepoint, return false indicate the savepoint name doesn't exists.

func (*TransactionContext) FlushStmtPessimisticLockCache 

func (tc *TransactionContext) FlushStmtPessimisticLockCache()

FlushStmtPessimisticLockCache merges the current statement pessimistic lock cache into transaction pessimistic lock cache. The caller may need to clear the stmt cache itself.

func (*TransactionContext) GetCurrentSavepoint 

func (tc *TransactionContext) GetCurrentSavepoint() TxnCtxNeedToRestore

GetCurrentSavepoint gets TransactionContext's savepoint.

func (*TransactionContext) GetForUpdateTS 

func (tc *TransactionContext) GetForUpdateTS() uint64

GetForUpdateTS returns the ts for update.

func (*TransactionContext) GetKeyInPessimisticLockCache 

func (tc *TransactionContext) GetKeyInPessimisticLockCache(key kv.Key) (val []byte, ok bool)

GetKeyInPessimisticLockCache gets a key in pessimistic lock cache.

func (*TransactionContext) ReleaseSavepoint 

func (tc *TransactionContext) ReleaseSavepoint(name string) bool

ReleaseSavepoint deletes the named savepoint and the later savepoints, return false indicate the named savepoint doesn't exists.

func (*TransactionContext) RestoreBySavepoint 

func (tc *TransactionContext) RestoreBySavepoint(savepoint TxnCtxNeedToRestore)

RestoreBySavepoint restores TransactionContext to the specify savepoint.

func (*TransactionContext) RollbackToSavepoint 

func (tc *TransactionContext) RollbackToSavepoint(name string) *SavepointRecord

RollbackToSavepoint rollbacks to the specified savepoint by name.

func (*TransactionContext) SetForUpdateTS 

func (tc *TransactionContext) SetForUpdateTS(forUpdateTS uint64)

SetForUpdateTS sets the ts for update.

func (*TransactionContext) SetPessimisticLockCache 

func (tc *TransactionContext) SetPessimisticLockCache(key kv.Key, val []byte)

SetPessimisticLockCache sets a key value pair in pessimistic lock cache. The value is buffered in the statement cache until the current statement finishes.

func (*TransactionContext) UpdateDeltaForTable 

func (tc *TransactionContext) UpdateDeltaForTable(
	physicalTableID int64, delta int64,
	count int64, cols DeltaCols,
)

UpdateDeltaForTable updates the delta info for some table. The `cols` argument is used to update the delta size for cols. If `cols` is nil, it means that the delta size for cols is not changed.

type TxnCtxNeedToRestore 

type TxnCtxNeedToRestore struct {
	// TableDeltaMap is used in the schema validator for DDL changes in one table not to block others.
	// It's also used in the statistics updating.
	// Note: for the partitioned table, it stores all the partition IDs.
	TableDeltaMap map[int64]TableDelta

	// CachedTables is not nil if the transaction write on cached table.
	CachedTables map[int64]any

	// InsertTTLRowsCount counts how many rows are inserted in this statement
	InsertTTLRowsCount int
	// contains filtered or unexported fields
}

TxnCtxNeedToRestore stores transaction variables which need to be restored when rolling back to a savepoint.

type TxnCtxNoNeedToRestore 

type TxnCtxNoNeedToRestore struct {
	Binlog      any
	InfoSchema  any
	History     any
	StartTS     uint64
	StaleReadTs uint64

	PessimisticCacheHit int

	// CreateTime For metrics.
	CreateTime     time.Time
	StatementCount int
	CouldRetry     bool
	IsPessimistic  bool
	// IsStaleness indicates whether the txn is read only staleness txn.
	IsStaleness bool
	// IsExplicit indicates whether the txn is an interactive txn, which is typically started with a BEGIN
	// or START TRANSACTION statement, or by setting autocommit to 0.
	IsExplicit bool
	Isolation  string
	LockExpire uint32
	ForUpdate  uint32
	// TxnScope indicates the value of txn_scope
	TxnScope string

	// Savepoints contains all definitions of the savepoint of a transaction at runtime, the order of the SavepointRecord is the same with the SAVEPOINT statements.
	// It is used for a lookup when running `ROLLBACK TO` statement.
	Savepoints []SavepointRecord

	// TemporaryTables is used to store transaction-specific information for global temporary tables.
	// It can also be stored in sessionCtx with local temporary tables, but it's easier to clean this data after transaction ends.
	TemporaryTables map[int64]tableutil.TempTable
	// EnableMDL indicates whether to enable the MDL lock for the transaction.
	EnableMDL bool

	// FairLockingUsed marking whether at least one of the statements in the transaction was executed in
	// fair locking mode.
	FairLockingUsed bool
	// FairLockingEffective marking whether at least one of the statements in the transaction was executed in
	// fair locking mode, and it takes effect (which is determined according to whether lock-with-conflict
	// has occurred during execution of any statement).
	FairLockingEffective bool

	// CurrentStmtPessimisticLockCache is the cache for pessimistic locked keys in the current statement.
	// It is merged into `pessimisticLockCache` after a statement finishes.
	// Read results cannot be directly written into pessimisticLockCache because failed statement need to rollback
	// its pessimistic locks.
	CurrentStmtPessimisticLockCache map[string][]byte
	// contains filtered or unexported fields
}

TxnCtxNoNeedToRestore stores transaction variables which do not need to restored when rolling back to a savepoint.

type TxnReadTS 

type TxnReadTS struct {
	// contains filtered or unexported fields
}

TxnReadTS indicates the value and used situation for tx_read_ts

func NewTxnReadTS 

func NewTxnReadTS(ts uint64) *TxnReadTS

NewTxnReadTS creates TxnReadTS

func (*TxnReadTS) PeakTxnReadTS 

func (t *TxnReadTS) PeakTxnReadTS() uint64

PeakTxnReadTS returns readTS

func (*TxnReadTS) SetTxnReadTS 

func (t *TxnReadTS) SetTxnReadTS(ts uint64)

SetTxnReadTS update readTS, and refresh used

func (*TxnReadTS) UseTxnReadTS 

func (t *TxnReadTS) UseTxnReadTS() uint64

UseTxnReadTS returns readTS, and mark used as true

type TypeFlag 

type TypeFlag byte

TypeFlag is the SysVar type, which doesn't exactly match MySQL types.

type UserVars 

type UserVars struct {
	// contains filtered or unexported fields
}

UserVars is used to provide user variable operations.

func NewUserVars 

func NewUserVars() *UserVars

NewUserVars creates a new user UserVars object

func (*UserVars) Clone 

func (s *UserVars) Clone() UserVarsReader

Clone clones the user vars

func (*UserVars) GetUserVarType 

func (s *UserVars) GetUserVarType(name string) (*types.FieldType, bool)

GetUserVarType get user defined variables' type

func (*UserVars) GetUserVarVal 

func (s *UserVars) GetUserVarVal(name string) (types.Datum, bool)

GetUserVarVal get user defined variables' value

func (*UserVars) SetUserVarType 

func (s *UserVars) SetUserVarType(name string, ft *types.FieldType)

SetUserVarType set user defined variables' type

func (*UserVars) SetUserVarVal 

func (s *UserVars) SetUserVarVal(name string, dt types.Datum)

SetUserVarVal set user defined variables' value

func (*UserVars) UnsetUserVar 

func (s *UserVars) UnsetUserVar(varName string)

UnsetUserVar unset an user defined variable by name.

type UserVarsReader 

type UserVarsReader interface {
	// GetUserVarVal get user defined variables' value
	GetUserVarVal(name string) (types.Datum, bool)
	// GetUserVarType get user defined variables' type
	GetUserVarType(name string) (*types.FieldType, bool)
	// Clone clones the user vars
	Clone() UserVarsReader
}

UserVarsReader is used to read user defined variables.

type WriteStmtBufs 

type WriteStmtBufs struct {
	// RowValBuf is used by tablecodec.EncodeRow, to reduce runtime.growslice.
	RowValBuf []byte
	// AddRowValues use to store temp insert rows value, to reduce memory allocations when importing data.
	AddRowValues []types.Datum

	// IndexValsBuf is used by index.FetchValues
	IndexValsBuf []types.Datum
	// IndexKeyBuf is used by index.GenIndexKey
	IndexKeyBuf []byte
}

WriteStmtBufs can be used by insert/replace/delete/update statement. TODO: use a common memory pool to replace this.

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