opt

package
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 Go to latest Published: Sep 25, 2024 License: GPL-3.0, BSD-2-Clause Imports: 4 Imported by: 0

Documentation

Overview

Package opt provides sets of options used by LevelDB.

Index

Constants

View Source 
const (
	KiB = 1024
	MiB = KiB * 1024
	GiB = MiB * 1024
)

Variables

View Source 
var (
	DefaultBlockCacher                   = LRUCacher
	DefaultBlockCacheCapacity            = 8 * MiB
	DefaultBlockRestartInterval          = 16
	DefaultBlockSize                     = 4 * KiB
	DefaultCompactionExpandLimitFactor   = 25
	DefaultCompactionGPOverlapsFactor    = 10
	DefaultCompactionL0Trigger           = 4
	DefaultCompactionSourceLimitFactor   = 1
	DefaultCompactionTableSize           = 2 * MiB
	DefaultCompactionTableSizeMultiplier = 1.0
	DefaultCompactionTotalSize           = 10 * MiB
	DefaultCompactionTotalSizeMultiplier = 10.0
	DefaultCompressionType               = SnappyCompression
	DefaultIteratorSamplingRate          = 1 * MiB
	DefaultOpenFilesCacher               = LRUCacher
	DefaultOpenFilesCacheCapacity        = 500
	DefaultWriteBuffer                   = 4 * MiB
	DefaultWriteL0PauseTrigger           = 12
	DefaultWriteL0SlowdownTrigger        = 8
)
View Source 
var (
	// LRUCacher is the LRU-cache algorithm.
	LRUCacher = &CacherFunc{cache.NewLRU}

	// NoCacher is the value to disable caching algorithm.
	NoCacher = &CacherFunc{}
)

Functions

func GetStrict 

func GetStrict(o *Options, ro *ReadOptions, strict Strict) bool

Types

type Cacher 

type Cacher interface {
	New(capacity int) cache.Cacher
}

Cacher is a caching algorithm.

type CacherFunc 

type CacherFunc struct {
	NewFunc func(capacity int) cache.Cacher
}

func (*CacherFunc) New 

func (f *CacherFunc) New(capacity int) cache.Cacher

type Compression 

type Compression uint

Compression is the 'sorted table' block compression algorithm to use. 

const (
	DefaultCompression Compression = iota
	NoCompression
	SnappyCompression
)

func (Compression) String 

func (c Compression) String() string

type Options 

type Options struct {
	// AltFilters defines one or more 'alternative filters'.
	// 'alternative filters' will be used during reads if a filter block
	// does not match with the 'effective filter'.
	//
	// The default value is nil
	AltFilters []filter.Filter

	// BlockCacher provides cache algorithm for LevelDB 'sorted table' block caching.
	// Specify NoCacher to disable caching algorithm.
	//
	// The default value is LRUCacher.
	BlockCacher Cacher

	// BlockCacheCapacity defines the capacity of the 'sorted table' block caching.
	// Use -1 for zero, this has same effect as specifying NoCacher to BlockCacher.
	//
	// The default value is 8MiB.
	BlockCacheCapacity int

	// BlockRestartInterval is the number of keys between restart points for
	// delta encoding of keys.
	//
	// The default value is 16.
	BlockRestartInterval int

	// BlockSize is the minimum uncompressed size in bytes of each 'sorted table'
	// block.
	//
	// The default value is 4KiB.
	BlockSize int

	// CompactionExpandLimitFactor limits compaction size after expanded.
	// This will be multiplied by table size limit at compaction target level.
	//
	// The default value is 25.
	CompactionExpandLimitFactor int

	// CompactionGPOverlapsFactor limits overlaps in grandparent (Level + 2) that a
	// single 'sorted table' generates.
	// This will be multiplied by table size limit at grandparent level.
	//
	// The default value is 10.
	CompactionGPOverlapsFactor int

	// CompactionL0Trigger defines number of 'sorted table' at level-0 that will
	// trigger compaction.
	//
	// The default value is 4.
	CompactionL0Trigger int

	// CompactionSourceLimitFactor limits compaction source size. This doesn't apply to
	// level-0.
	// This will be multiplied by table size limit at compaction target level.
	//
	// The default value is 1.
	CompactionSourceLimitFactor int

	// CompactionTableSize limits size of 'sorted table' that compaction generates.
	// The limits for each level will be calculated as:
	//   CompactionTableSize * (CompactionTableSizeMultiplier ^ Level)
	// The multiplier for each level can also fine-tuned using CompactionTableSizeMultiplierPerLevel.
	//
	// The default value is 2MiB.
	CompactionTableSize int

	// CompactionTableSizeMultiplier defines multiplier for CompactionTableSize.
	//
	// The default value is 1.
	CompactionTableSizeMultiplier float64

	// CompactionTableSizeMultiplierPerLevel defines per-level multiplier for
	// CompactionTableSize.
	// Use zero to skip a level.
	//
	// The default value is nil.
	CompactionTableSizeMultiplierPerLevel []float64

	// CompactionTotalSize limits total size of 'sorted table' for each level.
	// The limits for each level will be calculated as:
	//   CompactionTotalSize * (CompactionTotalSizeMultiplier ^ Level)
	// The multiplier for each level can also fine-tuned using
	// CompactionTotalSizeMultiplierPerLevel.
	//
	// The default value is 10MiB.
	CompactionTotalSize int

	// CompactionTotalSizeMultiplier defines multiplier for CompactionTotalSize.
	//
	// The default value is 10.
	CompactionTotalSizeMultiplier float64

	// CompactionTotalSizeMultiplierPerLevel defines per-level multiplier for
	// CompactionTotalSize.
	// Use zero to skip a level.
	//
	// The default value is nil.
	CompactionTotalSizeMultiplierPerLevel []float64

	// Comparer defines a total ordering over the space of []byte keys: a 'less
	// than' relationship. The same comparison algorithm must be used for reads
	// and writes over the lifetime of the DB.
	//
	// The default value uses the same ordering as bytes.Compare.
	Comparer comparer.Comparer

	// Compression defines the 'sorted table' block compression to use.
	//
	// The default value (DefaultCompression) uses snappy compression.
	Compression Compression

	// DisableBufferPool allows disable use of util.BufferPool functionality.
	//
	// The default value is false.
	DisableBufferPool bool

	// DisableBlockCache allows disable use of cache.Cache functionality on
	// 'sorted table' block.
	//
	// The default value is false.
	DisableBlockCache bool

	// DisableCompactionBackoff allows disable compaction retry backoff.
	//
	// The default value is false.
	DisableCompactionBackoff bool

	// DisableLargeBatchTransaction allows disabling switch-to-transaction mode
	// on large batch write. If enable batch writes large than WriteBuffer will
	// use transaction.
	//
	// The default is false.
	DisableLargeBatchTransaction bool

	// ErrorIfExist defines whether an error should returned if the DB already
	// exist.
	//
	// The default value is false.
	ErrorIfExist bool

	// ErrorIfMissing defines whether an error should returned if the DB is
	// missing. If false then the database will be created if missing, otherwise
	// an error will be returned.
	//
	// The default value is false.
	ErrorIfMissing bool

	// Filter defines an 'effective filter' to use. An 'effective filter'
	// if defined will be used to generate per-table filter block.
	// The filter name will be stored on disk.
	// During reads LevelDB will try to find matching filter from
	// 'effective filter' and 'alternative filters'.
	//
	// Filter can be changed after a DB has been created. It is recommended
	// to put old filter to the 'alternative filters' to mitigate lack of
	// filter during transition period.
	//
	// A filter is used to reduce disk reads when looking for a specific key.
	//
	// The default value is nil.
	Filter filter.Filter

	// IteratorSamplingRate defines approximate gap (in bytes) between read
	// sampling of an iterator. The samples will be used to determine when
	// compaction should be triggered.
	//
	// The default is 1MiB.
	IteratorSamplingRate int

	// NoSync allows completely disable fsync.
	//
	// The default is false.
	NoSync bool

	// NoWriteMerge allows disabling write merge.
	//
	// The default is false.
	NoWriteMerge bool

	// OpenFilesCacher provides cache algorithm for open files caching.
	// Specify NoCacher to disable caching algorithm.
	//
	// The default value is LRUCacher.
	OpenFilesCacher Cacher

	// OpenFilesCacheCapacity defines the capacity of the open files caching.
	// Use -1 for zero, this has same effect as specifying NoCacher to OpenFilesCacher.
	//
	// The default value is 500.
	OpenFilesCacheCapacity int

	// If true then opens DB in read-only mode.
	//
	// The default value is false.
	ReadOnly bool

	// Strict defines the DB strict level.
	Strict Strict

	// WriteBuffer defines maximum size of a 'memdb' before flushed to
	// 'sorted table'. 'memdb' is an in-memory DB backed by an on-disk
	// unsorted journal.
	//
	// LevelDB may held up to two 'memdb' at the same time.
	//
	// The default value is 4MiB.
	WriteBuffer int

	// WriteL0StopTrigger defines number of 'sorted table' at level-0 that will
	// pause write.
	//
	// The default value is 12.
	WriteL0PauseTrigger int

	// WriteL0SlowdownTrigger defines number of 'sorted table' at level-0 that
	// will trigger write slowdown.
	//
	// The default value is 8.
	WriteL0SlowdownTrigger int
}

Options holds the optional parameters for the DB at large.

func (*Options) GetAltFilters 

func (o *Options) GetAltFilters() []filter.Filter

func (*Options) GetBlockCacheCapacity 

func (o *Options) GetBlockCacheCapacity() int

func (*Options) GetBlockCacher 

func (o *Options) GetBlockCacher() Cacher

func (*Options) GetBlockRestartInterval 

func (o *Options) GetBlockRestartInterval() int

func (*Options) GetBlockSize 

func (o *Options) GetBlockSize() int

func (*Options) GetCompactionExpandLimit 

func (o *Options) GetCompactionExpandLimit(level int) int

func (*Options) GetCompactionGPOverlaps 

func (o *Options) GetCompactionGPOverlaps(level int) int

func (*Options) GetCompactionL0Trigger 

func (o *Options) GetCompactionL0Trigger() int

func (*Options) GetCompactionSourceLimit 

func (o *Options) GetCompactionSourceLimit(level int) int

func (*Options) GetCompactionTableSize 

func (o *Options) GetCompactionTableSize(level int) int

func (*Options) GetCompactionTotalSize 

func (o *Options) GetCompactionTotalSize(level int) int64

func (*Options) GetComparer 

func (o *Options) GetComparer() comparer.Comparer

func (*Options) GetCompression 

func (o *Options) GetCompression() Compression

func (*Options) GetDisableBlockCache 

func (o *Options) GetDisableBlockCache() bool

func (*Options) GetDisableBufferPool 

func (o *Options) GetDisableBufferPool() bool

func (*Options) GetDisableCompactionBackoff 

func (o *Options) GetDisableCompactionBackoff() bool

func (*Options) GetDisableLargeBatchTransaction 

func (o *Options) GetDisableLargeBatchTransaction() bool

func (*Options) GetErrorIfExist 

func (o *Options) GetErrorIfExist() bool

func (*Options) GetErrorIfMissing 

func (o *Options) GetErrorIfMissing() bool

func (*Options) GetFilter 

func (o *Options) GetFilter() filter.Filter

func (*Options) GetIteratorSamplingRate 

func (o *Options) GetIteratorSamplingRate() int

func (*Options) GetNoSync 

func (o *Options) GetNoSync() bool

func (*Options) GetNoWriteMerge 

func (o *Options) GetNoWriteMerge() bool

func (*Options) GetOpenFilesCacheCapacity 

func (o *Options) GetOpenFilesCacheCapacity() int

func (*Options) GetOpenFilesCacher 

func (o *Options) GetOpenFilesCacher() Cacher

func (*Options) GetReadOnly 

func (o *Options) GetReadOnly() bool

func (*Options) GetStrict 

func (o *Options) GetStrict(strict Strict) bool

func (*Options) GetWriteBuffer 

func (o *Options) GetWriteBuffer() int

func (*Options) GetWriteL0PauseTrigger 

func (o *Options) GetWriteL0PauseTrigger() int

func (*Options) GetWriteL0SlowdownTrigger 

func (o *Options) GetWriteL0SlowdownTrigger() int

type ReadOptions 

type ReadOptions struct {
	// DontFillCache defines whether block reads for this 'read operation'
	// should be cached. If false then the block will be cached. This does
	// not affects already cached block.
	//
	// The default value is false.
	DontFillCache bool

	// Strict will be OR'ed with global DB 'strict level' unless StrictOverride
	// is present. Currently only StrictReader that has effect here.
	Strict Strict
}

ReadOptions holds the optional parameters for 'read operation'. The 'read operation' includes Get, Find and NewIterator.

func (*ReadOptions) GetDontFillCache 

func (ro *ReadOptions) GetDontFillCache() bool

func (*ReadOptions) GetStrict 

func (ro *ReadOptions) GetStrict(strict Strict) bool

type Strict 

type Strict uint

Strict is the DB 'strict level'. 

const (
	// If present then a corrupted or invalid chunk or block in manifest
	// journal will cause an error instead of being dropped.
	// This will prevent database with corrupted manifest to be opened.
	StrictManifest Strict = 1 << iota

	// If present then journal chunk checksum will be verified.
	StrictJournalChecksum

	// If present then a corrupted or invalid chunk or block in journal
	// will cause an error instead of being dropped.
	// This will prevent database with corrupted journal to be opened.
	StrictJournal

	// If present then 'sorted table' block checksum will be verified.
	// This has effect on both 'read operation' and compaction.
	StrictBlockChecksum

	// If present then a corrupted 'sorted table' will fails compaction.
	// The database will enter read-only mode.
	StrictCompaction

	// If present then a corrupted 'sorted table' will halts 'read operation'.
	StrictReader

	// If present then leveldb.Recover will drop corrupted 'sorted table'.
	StrictRecovery

	// This only applicable for ReadOptions, if present then this ReadOptions
	// 'strict level' will override global ones.
	StrictOverride

	// StrictAll enables all strict flags.
	StrictAll = StrictManifest | StrictJournalChecksum | StrictJournal | StrictBlockChecksum | StrictCompaction | StrictReader | StrictRecovery

	// DefaultStrict is the default strict flags. Specify any strict flags
	// will override default strict flags as whole (i.e. not OR'ed).
	DefaultStrict = StrictJournalChecksum | StrictBlockChecksum | StrictCompaction | StrictReader

	// NoStrict disables all strict flags. Override default strict flags.
	NoStrict = ^StrictAll
)

type WriteOptions 

type WriteOptions struct {
	// NoWriteMerge allows disabling write merge.
	//
	// The default is false.
	NoWriteMerge bool

	// Sync is whether to sync underlying writes from the OS buffer cache
	// through to actual disk, if applicable. Setting Sync can result in
	// slower writes.
	//
	// If false, and the machine crashes, then some recent writes may be lost.
	// Note that if it is just the process that crashes (and the machine does
	// not) then no writes will be lost.
	//
	// In other words, Sync being false has the same semantics as a write
	// system call. Sync being true means write followed by fsync.
	//
	// The default value is false.
	Sync bool
}

WriteOptions holds the optional parameters for 'write operation'. The 'write operation' includes Write, Put and Delete.

func (*WriteOptions) GetNoWriteMerge 

func (wo *WriteOptions) GetNoWriteMerge() bool

func (*WriteOptions) GetSync 

func (wo *WriteOptions) GetSync() bool

Source Files

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