leveldb

Documentation

Overview

Package leveldb is a wrapper of goleveldb.

Index

• func IsNotFoundErr(err error) bool
• type Batch
• type Batcher
• type Compacter
• type Database
  • func New(path string, cache int, handles int, readonly bool) (*Database, error)
  • func NewCustom(path string, customize func(options *opt.Options)) (*Database, error)
  • func (db *Database) Close() error
  • func (db *Database) Compact(start []byte, limit []byte) error
  • func (db *Database) Delete(key []byte) error
  • func (db *Database) Get(key []byte) ([]byte, error)
  • func (db *Database) Has(key []byte) (bool, error)
  • func (db *Database) NewBatch() Batch
  • func (db *Database) NewIterator(prefix []byte, start []byte) Iterator
  • func (db *Database) Path() string
  • func (db *Database) Put(key []byte, value []byte) error
  • func (db *Database) Stat(property string) (string, error)
• type HookedBatch
  • func (b HookedBatch) Delete(key []byte) error
  • func (b HookedBatch) Put(key []byte, value []byte) error
• type Iteratee
• type Iterator
• type KeyValueReader
• type KeyValueStore
• type KeyValueWriter
• type Stater

Functions

func IsNotFoundErr

func IsNotFoundErr(err error) bool

IsNotFoundErr is err 'ErrNotFound'

Types

type Batch

type Batch interface {
	KeyValueWriter

	// ValueSize retrieves the amount of data queued up for writing.
	ValueSize() int

	// Write flushes any accumulated data to disk.
	Write() error

	// Reset resets the batch for reuse.
	Reset()

	// Replay replays the batch contents.
	Replay(w KeyValueWriter) error
}

Batch is a write-only database that commits changes to its host database when Write is called. A batch cannot be used concurrently.

type Batcher

type Batcher interface {
	// NewBatch creates a write-only database that buffers changes to its host db
	// until a final write is called.
	NewBatch() Batch
}

Batcher wraps the NewBatch method of a backing data store.

type Compacter

type Compacter interface {
	// Compact flattens the underlying data store for the given key range. In essence,
	// deleted and overwritten versions are discarded, and the data is rearranged to
	// reduce the cost of operations needed to access them.
	//
	// A nil start is treated as a key before all keys in the data store; a nil limit
	// is treated as a key after all keys in the data store. If both is nil then it
	// will compact entire data store.
	Compact(start []byte, limit []byte) error
}

Compacter wraps the Compact method of a backing data store.

type Database

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

Database is a persistent key-value store. Apart from basic data storage functionality it also supports batch writes and iterating over the keyspace in binary-alphabetical order.

func New

func New(path string, cache int, handles int, readonly bool) (*Database, error)

New returns a wrapped LevelDB object.

func NewCustom

func NewCustom(path string, customize func(options *opt.Options)) (*Database, error)

NewCustom returns a wrapped LevelDB object. The customize function allows the caller to modify the leveldb options.

func (*Database) Close

func (db *Database) Close() error

Close flushes any pending data to disk and closes all io accesses to the underlying key-value store.

func (*Database) Compact

func (db *Database) Compact(start []byte, limit []byte) error

Compact flattens the underlying data store for the given key range. In essence, deleted and overwritten versions are discarded, and the data is rearranged to reduce the cost of operations needed to access them.

A nil start is treated as a key before all keys in the data store; a nil limit is treated as a key after all keys in the data store. If both is nil then it will compact entire data store.

func (*Database) Delete

func (db *Database) Delete(key []byte) error

Delete removes the key from the key-value store.

func (*Database) Get

func (db *Database) Get(key []byte) ([]byte, error)

Get retrieves the given key if it's present in the key-value store.

func (*Database) Has

func (db *Database) Has(key []byte) (bool, error)

Has retrieves if a key is present in the key-value store.

func (*Database) NewBatch

func (db *Database) NewBatch() Batch

NewBatch creates a write-only key-value store that buffers changes to its host database until a final write is called.

func (*Database) NewIterator

func (db *Database) NewIterator(prefix []byte, start []byte) Iterator

NewIterator creates a binary-alphabetical iterator over a subset of database content with a particular key prefix, starting at a particular initial key (or after, if it does not exist).

func (*Database) Path

func (db *Database) Path() string

Path returns the path to the database directory.

func (*Database) Put

func (db *Database) Put(key []byte, value []byte) error

Put inserts the given value into the key-value store.

func (*Database) Stat

func (db *Database) Stat(property string) (string, error)

Stat returns a particular internal stat of the database.

type HookedBatch

type HookedBatch struct {
	Batch

	OnPut    func(key []byte, value []byte) // Callback if a key is inserted
	OnDelete func(key []byte)               // Callback if a key is deleted
}

HookedBatch wraps an arbitrary batch where each operation may be hooked into to monitor from black box code.

func (HookedBatch) Delete

func (b HookedBatch) Delete(key []byte) error

Delete removes the key from the key-value data store.

func (HookedBatch) Put

func (b HookedBatch) Put(key []byte, value []byte) error

Put inserts the given value into the key-value data store.

type Iteratee

type Iteratee interface {
	// NewIterator creates a binary-alphabetical iterator over a subset
	// of database content with a particular key prefix, starting at a particular
	// initial key (or after, if it does not exist).
	//
	// Note: This method assumes that the prefix is NOT part of the start, so there's
	// no need for the caller to prepend the prefix to the start
	NewIterator(prefix []byte, start []byte) Iterator
}

Iteratee wraps the NewIterator methods of a backing data store.

type Iterator

type Iterator interface {
	// Next moves the iterator to the next key/value pair. It returns whether the
	// iterator is exhausted.
	Next() bool

	// Error returns any accumulated error. Exhausting all the key/value pairs
	// is not considered to be an error.
	Error() error

	// Key returns the key of the current key/value pair, or nil if done. The caller
	// should not modify the contents of the returned slice, and its contents may
	// change on the next call to Next.
	Key() []byte

	// Value returns the value of the current key/value pair, or nil if done. The
	// caller should not modify the contents of the returned slice, and its contents
	// may change on the next call to Next.
	Value() []byte

	// Release releases associated resources. Release should always succeed and can
	// be called multiple times without causing error.
	Release()
}

Iterator iterates over a database's key/value pairs in ascending key order.

When it encounters an error any seek will return false and will yield no key/ value pairs. The error can be queried by calling the Error method. Calling Release is still necessary.

An iterator must be released after use, but it is not necessary to read an iterator until exhaustion. An iterator is not safe for concurrent use, but it is safe to use multiple iterators concurrently.

type KeyValueReader

type KeyValueReader interface {
	// Has retrieves if a key is present in the key-value data store.
	Has(key []byte) (bool, error)

	// Get retrieves the given key if it's present in the key-value data store.
	Get(key []byte) ([]byte, error)
}

KeyValueReader wraps the Has and Get method of a backing data store.

type KeyValueStore

type KeyValueStore interface {
	KeyValueReader
	KeyValueWriter
	Batcher
	Iteratee
	Stater
	Compacter
	io.Closer
}

KeyValueStore contains all the methods required to allow handling different key-value data stores backing the high level database.

type KeyValueWriter

type KeyValueWriter interface {
	// Put inserts the given value into the key-value data store.
	Put(key []byte, value []byte) error

	// Delete removes the key from the key-value data store.
	Delete(key []byte) error
}

KeyValueWriter wraps the Put method of a backing data store.

type Stater

type Stater interface {
	// Stat returns a particular internal stat of the database.
	Stat(property string) (string, error)
}

Stater wraps the Stat method of a backing data store.