vardef

Documentation

Index

• Constants
• Variables
• func GetDDLErrorCountLimit() int64
• func GetDDLFlashbackConcurrency() int32
• func GetDDLReorgBatchSize() int32
• func GetDDLReorgRowFormat() int64
• func GetDDLReorgWorkerCounter() int32
• func GetMaxDeltaSchemaCount() int64
• func SetDDLErrorCountLimit(cnt int64)
• func SetDDLFlashbackConcurrency(cnt int32)
• func SetDDLReorgBatchSize(cnt int32)
• func SetDDLReorgRowFormat(format int64)
• func SetDDLReorgWorkerCounter(cnt int32)
• func SetMaxDeltaSchemaCount(cnt int64)
• type ClusteredIndexDefMode
  • func TiDBOptEnableClustered(opt string) ClusteredIndexDefMode
• type ExchangeCompressionMode
  • func ToExchangeCompressionMode(name string) (ExchangeCompressionMode, bool)
  • func (t ExchangeCompressionMode) Name() string
  • func (t ExchangeCompressionMode) ToTipbCompressionMode() tipb.CompressionMode
• type ScopeFlag
  • func (s ScopeFlag) String() string
• type TypeFlag

Constants

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"
)

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"
	// 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"
	// 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
	// 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"
	// 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"
)

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"

	// 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.

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"

	// TiDBAccelerateUserCreationUpdate decides whether tidb will load & update the whole user's data in-memory.
	TiDBAccelerateUserCreationUpdate = "tidb_accelerate_user_creation_update"
)

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

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"
	// TiDBCircuitBreakerPDMetadataErrorRateThresholdPct variable is used to set percent of errors to trip the circuit breaker for get region calls to PD
	// https://github.com/tikv/rfcs/blob/master/text/0115-circuit-breaker.md
	TiDBCircuitBreakerPDMetadataErrorRateThresholdPct = "tidb_cb_pd_metadata_error_rate_threshold_pct"
)

TiDB vars that have only global scope

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
)

TiDB intentional limits, can be raised in the future.

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                   = true
	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                    = ExchangeCompressionModeUnspecified
	DefTiDBEnableResourceControl                      = true
	DefTiDBResourceControlStrictMode                  = true
	DefTiDBPessimisticTransactionFairLocking          = false
	DefTiDBEnablePlanCacheForParamLimit               = true
	DefTiDBEnableINLJoinMultiPattern                  = true
	DefTiFlashComputeDispatchPolicy                   = 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                             = 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
	DefTiDBCircuitBreakerPDMetaErrorRatePct           = 0
	DefTiDBAccelerateUserCreationUpdate               = false
)

Default TiDB system variable values.

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"
)

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.

const (
	// AllReplicaStr is the string value of AllReplicas.
	AllReplicaStr = "all_replicas"
	// ClosestAdaptiveStr is the string value of ClosestAdaptive.
	ClosestAdaptiveStr = "closest_adaptive"
	// ClosestReplicasStr is the string value of ClosestReplicas.
	ClosestReplicasStr = "closest_replicas"
)

const (
	// DispatchPolicyRRStr is string value for DispatchPolicyRR.
	DispatchPolicyRRStr = "round_robin"
	// DispatchPolicyConsistentHashStr is string value for DispatchPolicyConsistentHash.
	DispatchPolicyConsistentHashStr = "consistent_hash"
	// DispatchPolicyInvalidStr is string value for DispatchPolicyInvalid.
	DispatchPolicyInvalidStr = "invalid"
)

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"
)

const (
	GlobalConfigEnableTopSQL = "enable_resource_metering"
	GlobalConfigSourceID     = "source_id"
)

Global config name list.

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"
)

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"
)

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

const ConcurrencyUnset = -1

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

Variables

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)
	DDLReorgWorkerCounter   int32 = DefTiDBDDLReorgWorkerCount
	DDLReorgBatchSize       int32 = DefTiDBDDLReorgBatchSize
	DDLFlashbackConcurrency int32 = DefTiDBDDLFlashbackConcurrency
	DDLErrorCountLimit      int64 = DefTiDBDDLErrorCountLimit
	DDLReorgRowFormat       int64 = DefTiDBRowFormatV2
	DDLReorgMaxWriteSpeed         = atomic.NewInt64(DefTiDBDDLReorgMaxWriteSpeed)
	MaxDeltaSchemaCount     int64 = DefTiDBMaxDeltaSchemaCount
	// 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))
	AccelerateUserCreationUpdate = atomic.NewBool(DefTiDBAccelerateUserCreationUpdate)
)

Process global variables.

var SetCharsetVariables = []string{
	CharacterSetClient,
	CharacterSetResults,
}

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

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

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

Functions

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 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 SetMaxDeltaSchemaCount

func SetMaxDeltaSchemaCount(cnt int64)

SetMaxDeltaSchemaCount sets MaxDeltaSchemaCount size.

Types

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 ExchangeCompressionMode

type ExchangeCompressionMode int

ExchangeCompressionMode means the compress method used in exchange operator

const (
	// ExchangeCompressionModeNONE indicates no compression
	ExchangeCompressionModeNONE ExchangeCompressionMode = iota
	// ExchangeCompressionModeFast indicates fast compression/decompression speed, compression ratio is lower than HC mode
	ExchangeCompressionModeFast
	// ExchangeCompressionModeHC indicates high compression (HC) ratio mode
	ExchangeCompressionModeHC
	// ExchangeCompressionModeUnspecified indicates unspecified compress method, let TiDB choose one
	ExchangeCompressionModeUnspecified

	// RecommendedExchangeCompressionMode indicates recommended compression mode
	RecommendedExchangeCompressionMode ExchangeCompressionMode = ExchangeCompressionModeFast
)

func ToExchangeCompressionMode

func ToExchangeCompressionMode(name string) (ExchangeCompressionMode, bool)

ToExchangeCompressionMode returns the ExchangeCompressionMode from name

func (ExchangeCompressionMode) Name

func (t ExchangeCompressionMode) Name() string

Name returns the name of ExchangeCompressionMode

func (ExchangeCompressionMode) ToTipbCompressionMode

func (t ExchangeCompressionMode) ToTipbCompressionMode() tipb.CompressionMode

ToTipbCompressionMode returns tipb.CompressionMode from kv.ExchangeCompressionMode

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 TypeFlag

type TypeFlag byte

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