epos

README

README for epos

Introduction

epos is an embeddable persistent object store (hence the name) written in Go, to be used to store, update and query objects to a local file-based store.

License

See file LICENSE for details.

API Documentation

You can find the latest API documentation here: http://go.pkgdoc.org/github.com/akrennmair/epos

Author

Andreas Krennmair ak@synflood.at

Documentation

Index

• func RegisterStorageBackend(name string, factoryFunc func(path string) StorageBackend) error
• type And
• type Collection
  • func (c *Collection) AddIndex(field string) error
  • func (c *Collection) Delete(id Id) error
  • func (c *Collection) Insert(value interface{}) (Id, error)
  • func (c *Collection) Query(q Condition) (*Result, error)
  • func (c *Collection) QueryAll() (*Result, error)
  • func (c *Collection) QueryId(id Id) (*Result, error)
  • func (c *Collection) Reindex(field string) error
  • func (c *Collection) RemoveIndex(field string) error
  • func (c *Collection) Update(id Id, value interface{}) error
  • func (c *Collection) Vacuum() error
• type Condition
  • func Expression(s string) (Condition, error)
• type Database
  • func OpenDatabase(path string, typ StorageType) (*Database, error)
  • func (db *Database) Close() error
  • func (db *Database) Coll(name string) *Collection
  • func (db *Database) Collections() ([]string, error)
  • func (db *Database) Remove() error
  • func (db *Database) Vacuum() error
• type DiskvStorageBackend
  • func (s *DiskvStorageBackend) Erase(key string) error
  • func (s *DiskvStorageBackend) Keys() <-chan string
  • func (s *DiskvStorageBackend) Read(key string) ([]byte, error)
  • func (s *DiskvStorageBackend) Write(key string, value []byte) error
• type Equals
• type Id
• type LevelDBStorageBackend
  • func (s *LevelDBStorageBackend) Erase(key string) error
  • func (s *LevelDBStorageBackend) Keys() <-chan string
  • func (s *LevelDBStorageBackend) Read(key string) ([]byte, error)
  • func (s *LevelDBStorageBackend) Write(key string, value []byte) error
• type Or
• type Result
  • func (r *Result) Next(id *Id, result interface{}) bool
• type StorageBackend
  • func NewDiskvStorageBackend(path string) StorageBackend
  • func NewLevelDBStorageBackend(path string) StorageBackend
• type StorageType

Functions

func RegisterStorageBackend

func RegisterStorageBackend(name string, factoryFunc func(path string) StorageBackend) error

RegisterStorageBackend registers a new custom storage backend under a new name. If the name is already used, an error is returned.

In order to create a new custom storage backend, the programmer must also provide a function that takes the path where the storage backend must write its data (as a single file or within a directory) and that returns an object that satisfies the interface StorageBackend

Types

type And

type And []Condition

type Collection

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

func (*Collection) AddIndex

func (c *Collection) AddIndex(field string) error

AddIndex creates an index for a field. Existing records will be indexed, and future insert and update operations will index that field, as well. If an index for that field already exists, the AddIndex() is a no-op.

A field describes a top-level element of a struct or a particular key of a map.

func (*Collection) Delete

func (c *Collection) Delete(id Id) error

Delete deletes an object, identified by its ID, from the collection.

func (*Collection) Insert

func (c *Collection) Insert(value interface{}) (Id, error)

Insert inserts an object into the collection. It returns the object's ID and, if the insert fails, a non-nil error describing the problem.

func (*Collection) Query

func (c *Collection) Query(q Condition) (*Result, error)

Query takes a query in the form of a (possibly nested) Condition, and returns a Result object.

func (*Collection) QueryAll

func (c *Collection) QueryAll() (*Result, error)

QueryAll returns a Result object that will deliver all objects in the object store in no particular order.

func (*Collection) QueryId

func (c *Collection) QueryId(id Id) (*Result, error)

QueryId returns a Result object that will exactly deliver the object with the requested ID.

func (*Collection) Reindex

func (c *Collection) Reindex(field string) error

Reindex deletes and recreates the index for a field.

func (*Collection) RemoveIndex

func (c *Collection) RemoveIndex(field string) error

RemoveIndex removes an existing index for a field. It returns a non-nil error if an error occurs.

func (*Collection) Update

func (c *Collection) Update(id Id, value interface{}) error

Update replaces an existing object with a new object. If an error occurs during that operation, it returns a non-nil error.

func (*Collection) Vacuum

func (c *Collection) Vacuum() error

Vacuum expunges old entries that refer to deleted objects from all indexes of a collection.

type Condition

type Condition interface {
	// contains filtered or unexported methods
}

func Expression

func Expression(s string) (Condition, error)

Expression converts a S-Expr-based query to a structure of Condition objects. The following symbols are available for queries:

(id 1)					query entry with ID 1
(eq field-name value)		query all entries where field-name equals value
(or expr...)              OR all query sub-expressions
(and expr...)             AND all query sub-expressions

type Database

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

func OpenDatabase

func OpenDatabase(path string, typ StorageType) (*Database, error)

OpenDatabase opens and if necessary creates a database identified by the provided path. It returns a database object and a non-nil error if an error occured while opening or creating the database.

func (*Database) Close

func (db *Database) Close() error

Close closes the database and frees the memory associated with all collections.

func (*Database) Coll

func (db *Database) Coll(name string) *Collection

Coll returns the collection of the specified name. If the collection doesn't exist yet, it is opened and/or created on the fly.

func (*Database) Collections

func (db *Database) Collections() ([]string, error)

Collections returns a list of collection names that are currently in the database.

func (*Database) Remove

func (db *Database) Remove() error

Remove physically removes the database from the filesystem. WARNING: unless you have proper backups or snapshots from your filesystem, this operation is irreversible and leads to permanent data loss.

func (*Database) Vacuum

func (db *Database) Vacuum() error

Vacuum calls Vacuum on all open collections.

type DiskvStorageBackend

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

func (*DiskvStorageBackend) Erase

func (s *DiskvStorageBackend) Erase(key string) error

func (*DiskvStorageBackend) Keys

func (s *DiskvStorageBackend) Keys() <-chan string

func (*DiskvStorageBackend) Read

func (s *DiskvStorageBackend) Read(key string) ([]byte, error)

func (*DiskvStorageBackend) Write

func (s *DiskvStorageBackend) Write(key string, value []byte) error

type Equals

type Equals struct {
	Field string
	Value interface{}
}

type Id

type Id int64

type LevelDBStorageBackend

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

func (*LevelDBStorageBackend) Erase

func (s *LevelDBStorageBackend) Erase(key string) error

func (*LevelDBStorageBackend) Keys

func (s *LevelDBStorageBackend) Keys() <-chan string

func (*LevelDBStorageBackend) Read

func (s *LevelDBStorageBackend) Read(key string) ([]byte, error)

func (*LevelDBStorageBackend) Write

func (s *LevelDBStorageBackend) Write(key string, value []byte) error

type Or

type Or []Condition

type Result

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

func (*Result) Next

func (r *Result) Next(id *Id, result interface{}) bool

type StorageBackend

type StorageBackend interface {
	Read(key string) ([]byte, error)
	Write(key string, value []byte) error
	Erase(key string) error
	Keys() <-chan string
}

func NewDiskvStorageBackend

func NewDiskvStorageBackend(path string) StorageBackend

func NewLevelDBStorageBackend

func NewLevelDBStorageBackend(path string) StorageBackend

type StorageType

type StorageType string

const (
	STORAGE_AUTO    StorageType = "auto"
	STORAGE_DISKV   StorageType = "diskv"
	STORAGE_LEVELDB StorageType = "leveldb"
)