Documentation ¶
Overview ¶
Package opt provides sets of options used by LevelDB.
Index ¶
- Constants
- Variables
- func GetStrict(o *Options, ro *ReadOptions, strict Strict) bool
- type Cacher
- type CacherFunc
- type Compression
- type Options
- func (o *Options) GetAltFilters() []filter.Filter
- func (o *Options) GetBlockCacheCapacity() int
- func (o *Options) GetBlockCacheEvictRemoved() bool
- func (o *Options) GetBlockCacher() Cacher
- func (o *Options) GetBlockRestartInterval() int
- func (o *Options) GetBlockSize() int
- func (o *Options) GetCompactionExpandLimit(level int) int
- func (o *Options) GetCompactionGPOverlaps(level int) int
- func (o *Options) GetCompactionL0Trigger() int
- func (o *Options) GetCompactionSourceLimit(level int) int
- func (o *Options) GetCompactionTableSize(level int) int
- func (o *Options) GetCompactionTotalSize(level int) int64
- func (o *Options) GetComparer() comparer.Comparer
- func (o *Options) GetCompression() Compression
- func (o *Options) GetDisableBlockCache() bool
- func (o *Options) GetDisableBufferPool() bool
- func (o *Options) GetDisableCompactionBackoff() bool
- func (o *Options) GetDisableLargeBatchTransaction() bool
- func (o *Options) GetErrorIfExist() bool
- func (o *Options) GetErrorIfMissing() bool
- func (o *Options) GetFilter() filter.Filter
- func (o *Options) GetIteratorSamplingRate() int
- func (o *Options) GetNoSync() bool
- func (o *Options) GetNoWriteMerge() bool
- func (o *Options) GetOpenFilesCacheCapacity() int
- func (o *Options) GetOpenFilesCacher() Cacher
- func (o *Options) GetReadOnly() bool
- func (o *Options) GetStrict(strict Strict) bool
- func (o *Options) GetWriteBuffer() int
- func (o *Options) GetWriteL0PauseTrigger() int
- func (o *Options) GetWriteL0SlowdownTrigger() int
- type ReadOptions
- type Strict
- type WriteOptions
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 ¶
Types ¶
type CacherFunc ¶
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 // BlockCacheEvictRemoved allows enable forced-eviction on cached block belonging // to removed 'sorted table'. // // The default if false. BlockCacheEvictRemoved bool // 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 (*Options) GetBlockCacheCapacity ¶
func (*Options) GetBlockCacheEvictRemoved ¶
func (*Options) GetBlockCacher ¶
func (*Options) GetBlockRestartInterval ¶
func (*Options) GetBlockSize ¶
func (*Options) GetCompactionExpandLimit ¶
func (*Options) GetCompactionGPOverlaps ¶
func (*Options) GetCompactionL0Trigger ¶
func (*Options) GetCompactionSourceLimit ¶
func (*Options) GetCompactionTableSize ¶
func (*Options) GetCompactionTotalSize ¶
func (*Options) GetComparer ¶
func (*Options) GetCompression ¶
func (o *Options) GetCompression() Compression
func (*Options) GetDisableBlockCache ¶
func (*Options) GetDisableBufferPool ¶
func (*Options) GetDisableCompactionBackoff ¶
func (*Options) GetDisableLargeBatchTransaction ¶
func (*Options) GetErrorIfExist ¶
func (*Options) GetErrorIfMissing ¶
func (*Options) GetIteratorSamplingRate ¶
func (*Options) GetNoWriteMerge ¶
func (*Options) GetOpenFilesCacheCapacity ¶
func (*Options) GetOpenFilesCacher ¶
func (*Options) GetReadOnly ¶
func (*Options) GetWriteBuffer ¶
func (*Options) GetWriteL0PauseTrigger ¶
func (*Options) GetWriteL0SlowdownTrigger ¶
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
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