public class | source

CachedBackend

Implements:

IBackend

This is an intermediate layer caching the results of a backend. While simple get/put queries make use of the cache, more advanced queries will be forwarded to the backend.

Constructor Summary

Public Constructor
public	constructor(backend: IBackend) Creates a new instance of the cached layer using the specified backend.

Member Summary

Public Members
public get	connected: boolean
public get	indices: Map<string, IIndex> A map of index names to indices as defined by the underlying backend.

Method Summary

Public Methods
public abstract	async applyCombined(tx: Transaction): function() Returns the necessary information in order to flush a combined transaction.
public	close(): Promise Closes the object store and potential connections.
public	count(query: KeyRange): Promise<number> Returns the count of entries in the given range.
public	createIndex(indexName: string, keyPath: string \| Array<string>, options: IndexConfig): * Creates a new secondary index on the object store.
public	decode(value: , key: string): Method called to decode a single value.
public	deleteIndex(indexName: , options: function(oldVersion: number, newVersion: number): boolean}): Deletes a secondary index from the object store.
public	encode(value: ): Method called to encode a single value.
public	async get(key: string, options: RetrievalConfig): Promise<*> Returns a promise of the object stored under the given primary key.
public abstract	getSync(key: string, options: SyncRetrievalConfig): * Returns the object stored under the given primary key.
public	index(indexName: string): IIndex Returns the index of the given name.
public	isCached(key: string): boolean A check whether a certain key is cached.
public	isSynchronous(): boolean Checks whether an object store implements the ISynchronousObjectStore interface.
public	keyStream(callback: function(key: string): boolean, ascending: boolean, query: KeyRange): * Iterates over the keys in a given range and direction.
public	keys(query: Query \| KeyRange, limit: number): Promise<Set<string>> Returns a promise of a set of keys fulfilling the given query by querying the backend.
public	maxKey(query: KeyRange): Promise<string> Returns a promise of the key being maximal for the given range.
public	maxValue(query: KeyRange): Promise<*> Returns a promise of the object whose primary key is maximal for the given range.
public	minKey(query: KeyRange): Promise<string> Returns a promise of the key being minimal for the given range.
public	minValue(query: KeyRange): Promise<*> Returns a promise of the object whose primary key is minimal for the given range.
public	async truncate(): Promise Empties the object store.
public	valueStream(callback: function(value: , key: string): boolean, ascending: boolean, query: KeyRange): Iterates over the keys and values in a given range and direction.
public	values(query: Query \| KeyRange, limit: number): Promise<Array<*>> Returns a promise of an array of objects whose primary keys fulfill the given query by relying on the backend.

Protected Methods
protected	_apply(tx: Transaction): Promise Internally applies a transaction to the cache's and backend's state.
protected	_applyLocally(tx: Transaction) Internally applies a transaction to the cache's state.
protected	async _retrieveValues(keys: Set<string>): Promise<Array<*>> A helper method to retrieve the values corresponding to a set of keys.

Public Constructors

public constructor(backend: IBackend) source

Creates a new instance of the cached layer using the specified backend.

Params:

Name	Type	Attribute	Description
backend	IBackend		The backend to use.

Public Members

public get connected: boolean source

public get indices: Map<string, IIndex> source

A map of index names to indices as defined by the underlying backend. The index names can be used to access an index.

Public Methods

public abstract async applyCombined(tx: Transaction): function() source

Returns the necessary information in order to flush a combined transaction.

Params:

Name	Type	Attribute	Description
tx	Transaction		The transaction that should be applied to this backend.

Return:

function()

For non-persistent backends: a function that effectively applies the transaction. Native backends otherwise specify their own information as needed by their JungleDB instance.

public close(): Promise source

Closes the object store and potential connections.

Return:

Promise

The promise resolves after closing the object store.

public count(query: KeyRange): Promise<number> source

Returns the count of entries in the given range. If the optional query is not given, it returns the count of entries in the object store. If the query is of type KeyRange, it returns the count of entries within the given range.

Params:

Name	Type	Attribute	Description
query	KeyRange	optional

Return:

Promise<number>

public createIndex(indexName: string, keyPath: string | Array<string>, options: IndexConfig): * source

Creates a new secondary index on the object store. Currently, all secondary indices are non-unique. They are defined by a key within the object or alternatively a path through the object to a specific subkey. For example, ['a', 'b'] could be used to use 'key' as the key in the following object: { 'a': { 'b': 'key' } } Secondary indices may be multiEntry, i.e., if the keyPath resolves to an iterable object, each item within can be used to find this entry. If a new object does not possess the key path associated with that index, it is simply ignored.

This function may only be called before the database is connected. Moreover, it is only executed on database version updates or on first creation.

Params:

Name	Type	Attribute	Description
indexName	string		The name of the index.
keyPath	string \| Array<string>	optional	The path to the key within the object. May be an array for multiple levels.
options	IndexConfig	optional	An options object.

Return:

public decode(value: , key: string): source

Method called to decode a single value.

Params:

Name	Type	Attribute	Description
value	*		Value to be decoded.
key	string		Key corresponding to the value.

Return:

*	The decoded value.

public deleteIndex(indexName: , options: function(oldVersion: number, newVersion: number): boolean}): source

Deletes a secondary index from the object store.

Params:

Name	Type	Attribute	Description
indexName	*
options	function(oldVersion: number, newVersion: number): boolean}	optional

Return:

public encode(value: ): source

Method called to encode a single value.

Params:

Name	Type	Attribute	Description
value	*		Value to be encoded.

Return:

*	The encoded value.

public async get(key: string, options: RetrievalConfig): Promise<*> source

Returns a promise of the object stored under the given primary key. If the item is in the cache, the cached value will be returned. Otherwise, the value will be fetched from the backend object store.. Resolves to undefined if the key is not present in the object store.

Params:

Name	Type	Attribute	Description
key	string		The primary key to look for.
options	RetrievalConfig	optional	Advanced retrieval options.

Return:

Promise<*>

A promise of the object stored under the given key, or undefined if not present.

public abstract getSync(key: string, options: SyncRetrievalConfig): * source

Returns the object stored under the given primary key. Resolves to undefined if the key is not present in the object store.

Params:

Name	Type	Attribute	Description
key	string		The primary key to look for.
options	SyncRetrievalConfig	optional	Advanced retrieval options.

Return:

*	The object stored under the given key, or undefined if not present.

public index(indexName: string): IIndex source

Returns the index of the given name. If the index does not exist, it returns undefined.

Params:

Name	Type	Attribute	Description
indexName	string		The name of the requested index.

Return:

IIndex

The index associated with the given name.

public isCached(key: string): boolean source

A check whether a certain key is cached.

Params:

Name	Type	Attribute	Description
key	string		The key to check.

Return:

boolean

A boolean indicating whether the key is already in the cache.

public isSynchronous(): boolean source

Checks whether an object store implements the ISynchronousObjectStore interface.

Return:

boolean

The transaction object.

public keyStream(callback: function(key: string): boolean, ascending: boolean, query: KeyRange): * source

Iterates over the keys in a given range and direction. The callback is called for each primary key fulfilling the query until it returns false and stops the iteration.

Params:

Name	Type	Attribute	Description
callback	function(key: string): boolean		A predicate called for each key until returning false.
ascending	boolean		Determines the direction of traversal.
query	KeyRange		An optional KeyRange to narrow down the iteration space.

Return:

public keys(query: Query | KeyRange, limit: number): Promise<Set<string>> source

Returns a promise of a set of keys fulfilling the given query by querying the backend. If the optional query is not given, it returns all keys in the object store. If the query is of type KeyRange, it returns all keys of the object store being within this range. If the query is of type Query, it returns all keys fulfilling the query.

Params:

Name	Type	Attribute	Description
query	Query \| KeyRange	optional	Optional query to check keys against.
limit	number	optional	Limits the number of results if given.

Return:

Promise<Set<string>>

A promise of the set of keys relevant to the query.

public maxKey(query: KeyRange): Promise<string> source

Returns a promise of the key being maximal for the given range. If the optional query is not given, it returns the maximal key. If the query is of type KeyRange, it returns the key being maximal for the given range.

Params:

Name	Type	Attribute	Description
query	KeyRange	optional	Optional query to check keys against.

Return:

Promise<string>

A promise of the key relevant to the query.

public maxValue(query: KeyRange): Promise<*> source

Returns a promise of the object whose primary key is maximal for the given range. If the optional query is not given, it returns the object whose key is maximal. If the query is of type KeyRange, it returns the object whose primary key is maximal for the given range.

Params:

Name	Type	Attribute	Description
query	KeyRange	optional	Optional query to check keys against.

Return:

Promise<*>

A promise of the object relevant to the query.

public minKey(query: KeyRange): Promise<string> source

Returns a promise of the key being minimal for the given range. If the optional query is not given, it returns the minimal key. If the query is of type KeyRange, it returns the key being minimal for the given range.

Params:

Name	Type	Attribute	Description
query	KeyRange	optional	Optional query to check keys against.

Return:

Promise<string>

A promise of the key relevant to the query.

public minValue(query: KeyRange): Promise<*> source

Returns a promise of the object whose primary key is minimal for the given range. If the optional query is not given, it returns the object whose key is minimal. If the query is of type KeyRange, it returns the object whose primary key is minimal for the given range.

Params:

Name	Type	Attribute	Description
query	KeyRange	optional	Optional query to check keys against.

Return:

Promise<*>

A promise of the object relevant to the query.

public async truncate(): Promise source

Empties the object store.

Return:

Promise

The promise resolves after emptying the object store.

public valueStream(callback: function(value: , key: string): boolean, ascending: boolean, query: KeyRange): source

Iterates over the keys and values in a given range and direction. The callback is called for each value and primary key fulfilling the query until it returns false and stops the iteration.

Params:

Name	Type	Attribute	Description
callback	function(value: *, key: string): boolean		A predicate called for each value and key until returning false.
ascending	boolean		Determines the direction of traversal.
query	KeyRange		An optional KeyRange to narrow down the iteration space.

Return:

public values(query: Query | KeyRange, limit: number): Promise<Array<*>> source

Returns a promise of an array of objects whose primary keys fulfill the given query by relying on the backend. If the optional query is not given, it returns all objects in the object store. If the query is of type KeyRange, it returns all objects whose primary keys are within this range. If the query is of type Query, it returns all objects whose primary keys fulfill the query.

Params:

Name	Type	Attribute	Description
query	Query \| KeyRange	optional	Optional query to check keys against.
limit	number	optional	Limits the number of results if given.

Return:

Promise<Array<*>>

A promise of the array of objects relevant to the query.

Protected Methods

protected _apply(tx: Transaction): Promise source

Internally applies a transaction to the cache's and backend's state. This needs to be done in batch (as a db level transaction), i.e., either the full state is updated or no changes are applied.

Params:

Name	Type	Attribute	Description
tx	Transaction		The transaction to apply.

Return:

Promise

The promise resolves after applying the transaction.

protected _applyLocally(tx: Transaction) source

Internally applies a transaction to the cache's state.

Params:

Name	Type	Attribute	Description
tx	Transaction		The transaction to apply.

protected async _retrieveValues(keys: Set<string>): Promise<Array<*>> source

A helper method to retrieve the values corresponding to a set of keys.

Params:

Name	Type	Attribute	Description
keys	Set<string>		The set of keys to get the corresponding values for.

Return:

Promise<Array<*>>

A promise of the array of values.

CachedBackend

Implements:

Constructor Summary

Member Summary

Method Summary

Public Constructors

public constructor(backend: IBackend) source

Params:

Public Members

public get connected: boolean source

public get indices: Map<string, IIndex> source

Public Methods

public abstract async applyCombined(tx: Transaction): function() source

Params:

Return:

public close(): Promise source

Return:

public count(query: KeyRange): Promise<number> source

Params:

Return:

public createIndex(indexName: string, keyPath: string | Array<string>, options: IndexConfig): * source

Params:

Return:

public decode(value: *, key: string): * source

Params:

Return:

public deleteIndex(indexName: *, options: function(oldVersion: number, newVersion: number): boolean}): * source

Params:

Return:

public encode(value: *): * source

Params:

Return:

public async get(key: string, options: RetrievalConfig): Promise<*> source

Params:

Return:

public abstract getSync(key: string, options: SyncRetrievalConfig): * source

Params:

Return:

public index(indexName: string): IIndex source

Params:

Return:

public isCached(key: string): boolean source

Params:

Return:

public isSynchronous(): boolean source

Return:

public keyStream(callback: function(key: string): boolean, ascending: boolean, query: KeyRange): * source

Params:

Return:

public keys(query: Query | KeyRange, limit: number): Promise<Set<string>> source

Params:

Return:

public maxKey(query: KeyRange): Promise<string> source

Params:

Return:

public maxValue(query: KeyRange): Promise<*> source

Params:

Return:

public minKey(query: KeyRange): Promise<string> source

Params:

Return:

public minValue(query: KeyRange): Promise<*> source

Params:

Return:

public async truncate(): Promise source

Return:

public valueStream(callback: function(value: *, key: string): boolean, ascending: boolean, query: KeyRange): * source

Params:

Return:

public values(query: Query | KeyRange, limit: number): Promise<Array<*>> source

Params:

Return:

Protected Methods

protected _apply(tx: Transaction): Promise source

Params:

Return:

protected _applyLocally(tx: Transaction) source

Params:

protected async _retrieveValues(keys: Set<string>): Promise<Array<*>> source

Params:

public decode(value: , key: string): source

public deleteIndex(indexName: , options: function(oldVersion: number, newVersion: number): boolean}): source

public encode(value: ): source

public valueStream(callback: function(value: , key: string): boolean, ascending: boolean, query: KeyRange): source