keyvalue

Documentation

Overview

Package keyvalue implements a generic GraphStore for anything that implements the DB interface.

Index

• func EncodeKey(source *spb.VName, factName string, edgeKind string, target *spb.VName) ([]byte, error)
• func Entry(key []byte, val []byte) (*spb.Entry, error)
• func KeyPrefix(source *spb.VName, edgeKind string) ([]byte, error)
• type DB
• type Iterator
• type Options
  • func (o *Options) GetSnapshot() Snapshot
  • func (o *Options) IsLargeRead() bool
• type PoolOptions
• type Range
  • func KeyRange(k []byte) *Range
• type Snapshot
• type Store
  • func NewGraphStore(db DB) *Store
  • func (s *Store) Close(ctx context.Context) error
  • func (s *Store) Count(ctx context.Context, req *spb.CountRequest) (int64, error)
  • func (s *Store) Read(ctx context.Context, req *spb.ReadRequest, f graphstore.EntryFunc) error
  • func (s *Store) Scan(ctx context.Context, req *spb.ScanRequest, f graphstore.EntryFunc) error
  • func (s *Store) Shard(ctx context.Context, req *spb.ShardRequest, f graphstore.EntryFunc) error
  • func (s *Store) Write(ctx context.Context, req *spb.WriteRequest) (err error)
• type WritePool
  • func NewPool(db DB, opts *PoolOptions) *WritePool
  • func (p *WritePool) Flush() error
  • func (p *WritePool) Write(ctx context.Context, key, val []byte) error
• type Writer

Functions

func EncodeKey

func EncodeKey(source *spb.VName, factName string, edgeKind string, target *spb.VName) ([]byte, error)

EncodeKey returns a canonical encoding of an Entry (minus its value).

func Entry

func Entry(key []byte, val []byte) (*spb.Entry, error)

Entry decodes the key (assuming it was encoded by EncodeKey) into an Entry and populates its value field.

func KeyPrefix

func KeyPrefix(source *spb.VName, edgeKind string) ([]byte, error)

KeyPrefix returns a prefix to every encoded key for the given source VName and exact edgeKind. If edgeKind is "*", the prefix will match any edgeKind.

Types

type DB

type DB interface {
	// Get returns the value associated with the given key.  An io.EOF will be
	// returned if the key is not found.
	Get(context.Context, []byte, *Options) ([]byte, error)

	// ScanPrefix returns an Iterator for all key-values starting with the given
	// key prefix.  Options may be nil to use the defaults.
	ScanPrefix(context.Context, []byte, *Options) (Iterator, error)

	// ScanRange returns an Iterator for all key-values starting with the given
	// key range.  Options may be nil to use the defaults.
	ScanRange(context.Context, *Range, *Options) (Iterator, error)

	// Writer return a new write-access object
	Writer(context.Context) (Writer, error)

	// NewSnapshot returns a new consistent view of the DB that can be passed as
	// an option to DB scan methods.
	NewSnapshot(context.Context) Snapshot

	// Close release the underlying resources for the database.
	Close(context.Context) error
}

A DB is a sorted key-value store with read/write access. DBs must be Closed when no longer used to ensure resources are not leaked.

type Iterator

type Iterator interface {
	io.Closer

	// Next returns the currently positioned key-value entry and moves to the next
	// entry. If there is no key-value entry to return, an io.EOF error is
	// returned.
	Next() (key, val []byte, err error)

	// Seeks positions the Iterator to the given key.  The key must be further
	// than the current Iterator's position.  If the key does not exist, the
	// Iterator is positioned at the next existing key.  If no such key exists,
	// io.EOF is returned.
	Seek(key []byte) error
}

Iterator provides sequential access to a DB. Iterators must be Closed when no longer used to ensure that resources are not leaked.

type Options

type Options struct {
	// LargeRead expresses the client's intent that the read will likely be
	// "large" and the implementation should usually avoid certain behaviors such
	// as caching the entire visited key-value range.  Defaults to false.
	LargeRead bool

	// Snapshot causes the iterator to view the DB as it was at the Snapshot's
	// creation.
	Snapshot
}

Options alters the behavior of an Iterator.

func (*Options) GetSnapshot

func (o *Options) GetSnapshot() Snapshot

GetSnapshot returns the Snapshot option or the default of nil when o==nil.

func (*Options) IsLargeRead

func (o *Options) IsLargeRead() bool

IsLargeRead returns the LargeRead option or the default of false when o==nil.

type PoolOptions

type PoolOptions struct {
	// MaxWrites is the number of calls to Write before the WritePool
	// automatically flushes the underlying Writer.  This defaults to 32000
	// writes.
	MaxWrites int

	// MaxSize is the total size of the keys and values given to Write before the
	// WritePool automatically flushes the underlying Writer.  This defaults to
	// 32MiB.
	MaxSize datasize.Size
}

PoolOptions is a set of options used by WritePools.

type Range

type Range struct {
	Start, End []byte
}

Range is section of contiguous keys, including Start and excluding End.

func KeyRange

func KeyRange(k []byte) *Range

KeyRange returns a Range that contains only the given key.

type Snapshot

type Snapshot io.Closer

Snapshot is a consistent view of the DB.

type Store

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

A Store implements the graphstore.Service interface for a keyvalue DB

func NewGraphStore

func NewGraphStore(db DB) *Store

NewGraphStore returns a graphstore.Service backed by the given keyvalue DB.

func (*Store) Close

func (s *Store) Close(ctx context.Context) error

Close implements part of the graphstore.Service interface.

func (*Store) Count

func (s *Store) Count(ctx context.Context, req *spb.CountRequest) (int64, error)

Count implements part of the graphstore.Sharded interface.

func (*Store) Read

func (s *Store) Read(ctx context.Context, req *spb.ReadRequest, f graphstore.EntryFunc) error

Read implements part of the graphstore.Service interface.

func (*Store) Scan

func (s *Store) Scan(ctx context.Context, req *spb.ScanRequest, f graphstore.EntryFunc) error

Scan implements part of the graphstore.Service interface.

func (*Store) Shard

func (s *Store) Shard(ctx context.Context, req *spb.ShardRequest, f graphstore.EntryFunc) error

Shard implements part of the graphstore.Sharded interface.

func (*Store) Write

func (s *Store) Write(ctx context.Context, req *spb.WriteRequest) (err error)

Write implements part of the GraphStore interface.

type WritePool

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

WritePool is a wrapper around a DB that automatically creates and flushes Writers as data size is written, creating a simple buffered interface for writing to a DB. This interface is not thread-safe.

func NewPool

func NewPool(db DB, opts *PoolOptions) *WritePool

NewPool returns a new WritePool for the given DB. If opts==nil, its defaults are used.

func (*WritePool) Flush

func (p *WritePool) Flush() error

Flush ensures that all buffered writes are applied to the underlying DB.

func (*WritePool) Write

func (p *WritePool) Write(ctx context.Context, key, val []byte) error

Write buffers the given write until the pool becomes to large or Flush is called.

type Writer

type Writer interface {
	io.Closer

	// Write writes a key-value entry to the DB. Writes may be batched until the
	// Writer is Closed.
	Write(key, val []byte) error
}

Writer provides write access to a DB. Writes must be Closed when no longer used to ensure that resources are not leaked.