lm2

package module
v2.2.6+incompatible Latest Latest
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 Go to latest Published: Sep 25, 2018 License: BSD-3-Clause Imports: 10 Imported by: 15

README

lm2 CircleCI GoDoc

lm2 (listmap2) is an ordered key-value storage library.

It provides

  • Ordered key-value data model
  • Append-only modifications
  • Fully durable, atomic writes
  • Cursors with snapshot reads

Because it is append-only, records are never actually deleted. You will have to rewrite a collection to reclaim space.

License

BSD (see LICENSE)

Projects that use lm2

  • Transverse uses lm2 to store metadata, and uses lm2 through the Rig for synchronous replication.
  • Cistern uses lm2 for storing events.

Documentation

Index

Constants

This section is empty.

Variables

View Source 
var (
	// ErrDoesNotExist is returned when a collection's data file
	// doesn't exist.
	ErrDoesNotExist = errors.New("lm2: does not exist")
	// ErrInternal is returned when the internal state of the collection
	// is invalid. The collection should be closed and reopened.
	ErrInternal = errors.New("lm2: internal error")
	// ErrKeyNotFound is returned when a Cursor.Get() doesn't find
	// the requested key.
	ErrKeyNotFound = errors.New("lm2: key not found")
)

Functions

func IsRollbackError 

func IsRollbackError(err error) bool

IsRollbackError returns true if err is a RollbackError.

Types

type Collection 

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

Collection represents an ordered linked list map.

func NewCollection 

func NewCollection(file string, cacheSize int) (*Collection, error)

NewCollection creates a new collection with a data file at file. cacheSize represents the size of the collection cache.

func OpenCollection 

func OpenCollection(file string, cacheSize int) (*Collection, error)

OpenCollection opens a collection with a data file at file. cacheSize represents the size of the collection cache. ErrDoesNotExist is returned if file does not exist.

func (*Collection) Close 

func (c *Collection) Close()

Close closes a collection and all of its resources.

func (*Collection) Compact 

func (c *Collection) Compact() error

Compact rewrites a collection to clean up deleted records and optimize data layout on disk. NOTE: The collection is closed after compaction, so you'll have to reopen it.

func (*Collection) CompactFunc 

func (c *Collection) CompactFunc(f func(key, value string) (string, string, bool)) error

CompactFunc compacts with a custom compaction function. f is called with each key-value pair, and it should return the new key and value for that record if they should be changed, and whether to keep the record. Returning false will skip the record. NOTE: The collection is closed after compaction, so you'll have to reopen it.

func (*Collection) Destroy added in v1.2.1 

func (c *Collection) Destroy() error

Destroy closes the collection and removes its associated data files.

func (*Collection) NewCursor 

func (c *Collection) NewCursor() (*Cursor, error)

NewCursor returns a new cursor with a snapshot view of the current collection state.

func (*Collection) OK 

func (c *Collection) OK() bool

OK returns true if the internal state of the collection is valid. If false is returned you should close and reopen the collection.

func (*Collection) Stats added in v1.0.0 

func (c *Collection) Stats() Stats

Stats returns collection statistics.

func (*Collection) Update 

func (c *Collection) Update(wb *WriteBatch) (int64, error)

Update atomically and durably applies a WriteBatch (a set of updates) to the collection. It returns the new version (on success) and an error. The error may be a RollbackError; use IsRollbackError to check.

func (*Collection) Version added in v0.1.3 

func (c *Collection) Version() int64

Version returns the last committed version.

type Cursor 

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

Cursor represents a snapshot cursor.

func (*Cursor) Err added in v1.4.0 

func (c *Cursor) Err() error

Err returns the error encountered during iteration, if any.

func (*Cursor) Get 

func (c *Cursor) Get(key string) (string, error)

Get gets a single key using the cursor. This is just a helper function that seeks and finds a key for you. ErrKeyNotFound is returned as the error when the key is not found.

func (*Cursor) Key 

func (c *Cursor) Key() string

Key returns the key of the current record. It returns an empty string if the cursor is not valid.

func (*Cursor) Next 

func (c *Cursor) Next() bool

Next moves the cursor to the next record. It returns true if it lands on a valid record.

func (*Cursor) Seek 

func (c *Cursor) Seek(key string)

Seek positions the cursor at the last key less than or equal to the provided key.

func (*Cursor) Valid 

func (c *Cursor) Valid() bool

Valid returns true if the cursor's Key() and Value() methods can be called. It returns false if the cursor isn't at a valid record position.

func (*Cursor) Value 

func (c *Cursor) Value() string

Value returns the value of the current record. It returns an empty string if the cursor is not valid.

type RollbackError 

type RollbackError struct {
	DuplicateKey  bool
	ConflictedKey string
	Err           error
}

RollbackError is the error type returned after rollbacks.

func (RollbackError) Error 

func (e RollbackError) Error() string

type Stats added in v1.0.0 

type Stats struct {
	RecordsWritten uint64
	RecordsRead    uint64
	CacheHits      uint64
	CacheMisses    uint64
}

Stats holds collection statistics.

type WriteBatch 

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

WriteBatch represents a set of modifications.

func NewWriteBatch 

func NewWriteBatch() *WriteBatch

NewWriteBatch returns a new WriteBatch.

func (*WriteBatch) AllowOverwrite 

func (wb *WriteBatch) AllowOverwrite(allow bool)

AllowOverwrite determines whether keys will be overwritten. If allow is false and an existing key is being set, updates will be rolled back.

func (*WriteBatch) Delete 

func (wb *WriteBatch) Delete(key string)

Delete marks a key for deletion.

func (*WriteBatch) Set 

func (wb *WriteBatch) Set(key, value string)

Set adds key => value to the WriteBatch. Note: If a key is passed to Delete and Set, then the Set will be ignored.

func (*WriteBatch) SetSecureDelete 

func (wb *WriteBatch) SetSecureDelete(secureDelete bool)

SetSecureDelete determines whether record values are cleared with zero bytes when deleted.

Source Files

View all Source files

Directories

Path Synopsis
cmd
lm2util

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