store

Documentation

Index

• func MultiGet(kvreader KVReader, keys [][]byte) ([][]byte, error)
• type EmulatedBatch
  • func NewEmulatedBatch(mo MergeOperator) *EmulatedBatch
  • func (b *EmulatedBatch) Close() error
  • func (b *EmulatedBatch) Delete(key []byte)
  • func (b *EmulatedBatch) Merge(key, val []byte)
  • func (b *EmulatedBatch) Reset()
  • func (b *EmulatedBatch) Set(key, val []byte)
• type EmulatedMerge
  • func NewEmulatedMerge(mo MergeOperator) *EmulatedMerge
  • func (m *EmulatedMerge) Merge(key, val []byte)
• type KVBatch
• type KVBatchOptions
• type KVIterator
• type KVReader
• type KVStore
• type KVWriter
• type MergeOperator

Functions

func MultiGet

func MultiGet(kvreader KVReader, keys [][]byte) ([][]byte, error)

MultiGet is a helper function to retrieve mutiple keys from a KVReader, and might be used by KVStore implementations that don't have a native multi-get facility.

Types

type EmulatedBatch

type EmulatedBatch struct {
	Ops    []*op
	Merger *EmulatedMerge
}

func NewEmulatedBatch

func NewEmulatedBatch(mo MergeOperator) *EmulatedBatch

func (*EmulatedBatch) Close

func (b *EmulatedBatch) Close() error

func (*EmulatedBatch) Delete

func (b *EmulatedBatch) Delete(key []byte)

func (*EmulatedBatch) Merge

func (b *EmulatedBatch) Merge(key, val []byte)

func (*EmulatedBatch) Reset

func (b *EmulatedBatch) Reset()

func (*EmulatedBatch) Set

func (b *EmulatedBatch) Set(key, val []byte)

type EmulatedMerge

type EmulatedMerge struct {
	Merges map[string][][]byte
	// contains filtered or unexported fields
}

func NewEmulatedMerge

func NewEmulatedMerge(mo MergeOperator) *EmulatedMerge

func (*EmulatedMerge) Merge

func (m *EmulatedMerge) Merge(key, val []byte)

type KVBatch

type KVBatch interface {

	// Set updates the key with the specified value
	// both key and value []byte may be reused as soon as this call returns
	Set(key, val []byte)

	// Delete removes the specified key
	// the key []byte may be reused as soon as this call returns
	Delete(key []byte)

	// Merge merges old value with the new value at the specified key
	// as prescribed by the KVStores merge operator
	// both key and value []byte may be reused as soon as this call returns
	Merge(key, val []byte)

	// Reset frees resources for this batch and allows reuse
	Reset()

	// Close frees resources
	Close() error
}

KVBatch is an abstraction for making multiple KV mutations at once

type KVBatchOptions

type KVBatchOptions struct {
	// TotalBytes is the sum of key and value bytes needed by the
	// caller for the entire batch.  It affects the size of the
	// returned byte array of KVWrite.NewBatchEx().
	TotalBytes int

	// NumSets is the number of Set() calls the caller will invoke on
	// the KVBatch.
	NumSets int

	// NumMerges is the number of Merge() calls the caller will invoke
	// on the KVBatch.
	NumDeletes int

	// NumMerges is the number of Merge() calls the caller will invoke
	// on the KVBatch.
	NumMerges int
}

KVBatchOptions provides the KVWriter.NewBatchEx() method with batch preparation and preallocation information.

type KVIterator

type KVIterator interface {

	// Seek will advance the iterator to the specified key
	Seek(key []byte)

	// Next will advance the iterator to the next key
	Next()

	// Key returns the key pointed to by the iterator
	// The bytes returned are **ONLY** valid until the next call to Seek/Next/Close
	// Continued use after that requires that they be copied.
	Key() []byte

	// Value returns the value pointed to by the iterator
	// The bytes returned are **ONLY** valid until the next call to Seek/Next/Close
	// Continued use after that requires that they be copied.
	Value() []byte

	// Valid returns whether or not the iterator is in a valid state
	Valid() bool

	// Current returns Key(),Value(),Valid() in a single operation
	Current() ([]byte, []byte, bool)

	// Close closes the iterator
	Close() error
}

KVIterator is an abstraction around key iteration

type KVReader

type KVReader interface {

	// Get returns the value associated with the key
	// If the key does not exist, nil is returned.
	// The caller owns the bytes returned.
	Get(key []byte) ([]byte, error)

	// MultiGet retrieves multiple values in one call.
	MultiGet(keys [][]byte) ([][]byte, error)

	// PrefixIterator returns a KVIterator that will
	// visit all K/V pairs with the provided prefix
	PrefixIterator(prefix []byte) KVIterator

	// RangeIterator returns a KVIterator that will
	// visit all K/V pairs >= start AND < end
	RangeIterator(start, end []byte) KVIterator

	// Close closes the iterator
	Close() error
}

KVReader is an abstraction of an **ISOLATED** reader In this context isolated is defined to mean that writes/deletes made after the KVReader is opened are not observed. Because there is usually a cost associated with keeping isolated readers active, users should close them as soon as they are no longer needed.

type KVStore

type KVStore interface {

	// Writer returns a KVWriter which can be used to
	// make changes to the KVStore.  If a writer cannot
	// be obtained a non-nil error is returned.
	Writer() (KVWriter, error)

	// Reader returns a KVReader which can be used to
	// read data from the KVStore.  If a reader cannot
	// be obtained a non-nil error is returned.
	Reader() (KVReader, error)

	// Close closes the KVStore
	Close() error
}

KVStore is an abstraction for working with KV stores

type KVWriter

type KVWriter interface {

	// NewBatch returns a KVBatch for performing batch operations on this kvstore
	NewBatch() KVBatch

	// NewBatchEx returns a KVBatch and an associated byte array
	// that's pre-sized based on the KVBatchOptions.  The caller can
	// use the returned byte array for keys and values associated with
	// the batch.  Once the batch is either executed or closed, the
	// associated byte array should no longer be accessed by the
	// caller.
	NewBatchEx(KVBatchOptions) ([]byte, KVBatch, error)

	// ExecuteBatch will execute the KVBatch, the provided KVBatch **MUST** have
	// been created by the same KVStore (though not necessarily the same KVWriter)
	// Batch execution is atomic, either all the operations or none will be performed
	ExecuteBatch(batch KVBatch) error

	// Close closes the writer
	Close() error
}

KVWriter is an abstraction for mutating the KVStore KVWriter does **NOT** enforce restrictions of a single writer if the underlying KVStore allows concurrent writes, the KVWriter interface should also do so, it is up to the caller to do this in a way that is safe and makes sense

type MergeOperator

type MergeOperator interface {

	// FullMerge the full sequence of operands on top of the existingValue
	// if no value currently exists, existingValue is nil
	// return the merged value, and success/failure
	FullMerge(key, existingValue []byte, operands [][]byte) ([]byte, bool)

	// Partially merge these two operands.
	// If partial merge cannot be done, return nil,false, which will defer
	// all processing until the FullMerge is done.
	PartialMerge(key, leftOperand, rightOperand []byte) ([]byte, bool)

	// Name returns an identifier for the operator
	Name() string
}