db

Documentation

Index

• Constants
• type Batch
• type Batcher
• type Compacter
• type Database
• type Deleter
• type Iteratee
• type Iterator
• type KeyValueStore
• type Reader
• type Stater
• type Writer

Constants

const IdealBatchSize = 100 * 1024

IdealBatchSize defines the size of the data batches should ideally add in one write.

Types

type Batch

type Batch interface {
	Writer
	Deleter

	// 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()
}

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 interface {
	Reader
	Writer
	Deleter
	Batcher
	Iteratee
	Stater
	Compacter
	io.Closer
}

Database contains all the methods required by the high level database to not only access the key-value data store but also the chain freezer.

type Deleter

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

Deleter wraps the Delete method of a backing data store.

type Iteratee

type Iteratee interface {
	// NewIterator creates a binary-alphabetical iterator over the entire keyspace
	// contained within the key-value database.
	NewIterator() Iterator

	// NewIteratorWithPrefix creates a binary-alphabetical iterator over a subset
	// of database content with a particular key prefix.
	NewIteratorWithPrefix(prefix []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 KeyValueStore

type KeyValueStore interface {
	Reader
	Writer
	Deleter
	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 Reader

type Reader 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)
}

Reader wraps the Has and Get 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.

type Writer

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

Writer wraps the Put method of a backing data store.