public class | source

Snapshot

Extends:

Indirect Implements:

Snapshots present a read-only version of a specific state. As long as a snapshot is not aborted, the object store will reflect changes to the state in form of the differences to the originating state in the snapshot. This makes efficient queries against a fixed state possible without blocking other transactions to commit.

Constructor Summary

Protected Constructor
protected	constructor(objectStore: ObjectStore, backend: IObjectStore) This constructor should only be called by an ObjectStore object.

Method Summary

Public Methods
public	abort(tx: *): Promise<boolean> Aborts a snapshot and stops updating its diff.
public	close(): Promise Alias for abort.
public	async commit(tx: *) Unsupported operation for snapshots.
public	async put(key: , value: ): Promise Unsupported operation for snapshots.
public	putSync(key: , value: ) Unsupported operation for snapshots.
public	async remove(key: *): Promise Unsupported operation for snapshots.
public	removeSync(key: *) Unsupported operation for snapshots.
public	snapshot() Unsupported operation for snapshots.
public	synchronousTransaction() Unsupported operation for snapshots.
public	transaction() Unsupported operation for snapshots.
public	async truncate(): Promise Unsupported operation for snapshots.
public	truncateSync() Unsupported operation for snapshots.

Protected Methods
protected	async _apply(tx: Transaction): Promise Internally applies a transaction to the snapshot state.
protected	async _commitBackend(): Promise<boolean> Commits the transaction to the backend.
protected	async _commitInternal(tx: Transaction): Promise Unsupported operation for snapshots.
protected	_isCommittable(tx: Transaction): boolean Unsupported operation for snapshots.
protected	inherit(tx: Transaction): * A specific set of changes can be assumed to be already applied by providing a Transaction or Snapshot.

Inherited Summary

From class Transaction
public get	connected: boolean
public get	dependency: CombinedTransaction
public get	id: number
public get	indices: Map<string, IIndex> A map of index names to indices.
public get	nested: boolean
public get	objectStore: ObjectStore
public get	state: Transaction.STATE: * The transaction's current state.
public	async abort(tx: Transaction): Promise<boolean> Aborts a transaction and (if this was the last open transaction) potentially persists the most recent, committed state.
public	close(): Promise Alias for abort.
public	async commit(tx: Transaction): Promise<boolean> Commits a transaction to the underlying backend.
public	async count(query: KeyRange): Promise<number> Returns the count of entries in the given range.
public	decode(value: , key: string): Method called to decode a single value.
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	index(indexName: string): IIndex Returns the index of the given name.
public	isSynchronous(): boolean Checks whether an object store implements the ISynchronousObjectStore interface.
public	async keyStream(callback: function(key: string): boolean, ascending: boolean, query: KeyRange): Promise Iterates over the keys in a given range and direction.
public	async keys(query: Query \| KeyRange): Promise<Set<string>> Returns a promise of a set of keys fulfilling the given query.
public	async maxKey(query: KeyRange): Promise<string> Returns a promise of the key being maximal for the given range.
public	async maxValue(query: KeyRange): Promise<*> Returns a promise of the object whose primary key is maximal for the given range.
public	async minKey(query: KeyRange): Promise<string> Returns a promise of the key being minimal for the given range.
public	async minValue(query: KeyRange): Promise<*> Returns a promise of the object whose primary key is minimal for the given range.
public	async put(key: string, value: *): Promise Inserts or replaces a key-value pair.
public	putSync(key: string, value: *) Inserts or replaces a key-value pair.
public	async remove(key: string): Promise Removes the key-value pair of the given key from the object store.
public	removeSync(key: string) Removes the key-value pair of the given key from the object store.
public	snapshot(): Snapshot Creates an in-memory snapshot of this state.
public	synchronousTransaction(enableWatchdog: boolean): SynchronousTransaction Creates a nested synchronous transaction, ensuring read isolation.
public	toString(): string
public	toStringShort(): string
public	transaction(enableWatchdog: boolean): Transaction Creates a nested transaction, ensuring read isolation.
public	async truncate(): Promise Empties the object store.
public	async valueStream(callback: function(value: *, key: string): boolean, ascending: boolean, query: KeyRange): Promise Iterates over the keys and values in a given range and direction.
public	async values(query: Query \| KeyRange): Promise<Array<*>> Returns a promise of an array of objects whose primary keys fulfill the given query.
protected	async _apply(tx: Transaction): Promise Internally applies a transaction to the transaction'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.
protected	_applySync(tx: Transaction) Non-async version of _apply that does not update snapshots.
protected	async _checkConstraints(): Promise<boolean> Is used to check constraints before committing.
protected	async _commitBackend(): Promise<boolean> Commits the transaction to the backend.
protected	async _commitInternal(tx: Transaction): Promise Is used to commit the transaction to the in memory state.
protected	_isCommittable(tx: Transaction): boolean Is used to probe whether a transaction can be committed.
protected	_put(key: string, value: *) Internal method for inserting/replacing a key-value pair.
protected	_remove(key: string) Internal method for removing a key-value pair.
protected	_setParent(parent: *) Allows to change the backend of a Transaction when the state has been flushed.
protected	truncateSync() Non-async variant to empty the object store.

Protected Constructors

protected constructor(objectStore: ObjectStore, backend: IObjectStore) source

This constructor should only be called by an ObjectStore object.

Override:

Transaction#constructor

Params:

Name	Type	Attribute	Description
objectStore	ObjectStore		The object store this transaction belongs to.
backend	IObjectStore		The backend this transaction is based on.

Public Methods

public abort(tx: *): Promise<boolean> source

Aborts a snapshot and stops updating its diff.

Override:

Transaction#abort

Params:

Name	Type	Attribute	Description
tx	*	optional

Return:

Promise<boolean>

A promise of the success outcome.

public close(): Promise source

Alias for abort.

Override:

Transaction#close

Return:

Promise

The promise resolves after successful abortion of the transaction.

public async commit(tx: *) source

Unsupported operation for snapshots.

Override:

Transaction#commit

Params:

Name	Type	Attribute	Description
tx	*

Throw:

public async put(key: , value: ): Promise source

Unsupported operation for snapshots.

Override:

Transaction#put

Params:

Name	Type	Attribute	Description
key	*
value	*

Return:

Promise

public putSync(key: , value: ) source

Unsupported operation for snapshots.

Override:

Transaction#putSync

Params:

Name	Type	Attribute	Description
key	*
value	*

public async remove(key: *): Promise source

Unsupported operation for snapshots.

Override:

Transaction#remove

Params:

Name	Type	Attribute	Description
key	*

Return:

Promise

public removeSync(key: *) source

Unsupported operation for snapshots.

Override:

Transaction#removeSync

Params:

Name	Type	Attribute	Description
key	*

public snapshot() source

Unsupported operation for snapshots.

Override:

Transaction#snapshot

public synchronousTransaction() source

Unsupported operation for snapshots.

Override:

Transaction#synchronousTransaction

public transaction() source

Unsupported operation for snapshots.

Override:

Transaction#transaction

public async truncate(): Promise source

Unsupported operation for snapshots.

Override:

Transaction#truncate

Return:

Promise

public truncateSync() source

Unsupported operation for snapshots.

Override:

Transaction#truncateSync

Protected Methods

protected async _apply(tx: Transaction): Promise source

Internally applies a transaction to the snapshot state. In contrast to transactions, this tries to reflect the old state in the snapshot.

Override:

Transaction#_apply

Params:

Name	Type	Attribute	Description
tx	Transaction		The transaction to apply.

Return:

Promise

The promise resolves after applying the transaction.

protected async _commitBackend(): Promise<boolean> source

Commits the transaction to the backend.

Override:

Transaction#_commitBackend

Return:

Promise<boolean>

A promise of the success outcome.

protected async _commitInternal(tx: Transaction): Promise source

Unsupported operation for snapshots.

Override:

Transaction#_commitInternal

Params:

Name	Type	Attribute	Description
tx	Transaction		The transaction to be applied.

Return:

Promise

A promise that resolves upon successful application of the transaction.

protected _isCommittable(tx: Transaction): boolean source

Unsupported operation for snapshots.

Override:

Transaction#_isCommittable

Params:

Name	Type	Attribute	Description
tx	Transaction	optional	The transaction to be applied, if not given checks for the this transaction.

Return:

boolean

Whether a commit will be successful.

protected inherit(tx: Transaction): * source

A specific set of changes can be assumed to be already applied by providing a Transaction or Snapshot. These differences will be inherited while the backend of the snapshot remains the current state. This is useful, if we have a transaction/snapshot to a previous state, which we do not want to commit. Then, we can still base our snapshot on this earlier state although the current backend is already ahead.

Params:

Name	Type	Attribute	Description
tx	Transaction		A transaction or snapshot containing changes that have already been applied.

Snapshot

Extends:

Indirect Implements:

Constructor Summary

Method Summary

Inherited Summary

Protected Constructors

protected constructor(objectStore: ObjectStore, backend: IObjectStore) source

Override:

Params:

Public Methods

public abort(tx: *): Promise<boolean> source

Override:

Params:

Return:

public close(): Promise source

Override:

Return:

public async commit(tx: *) source

Override:

Params:

Throw:

public async put(key: *, value: *): Promise source

Override:

Params:

Return:

public putSync(key: *, value: *) source

Override:

Params:

public async remove(key: *): Promise source

Override:

Params:

Return:

public removeSync(key: *) source

Override:

Params:

public snapshot() source

Override:

public synchronousTransaction() source

Override:

public transaction() source

Override:

public async truncate(): Promise source

Override:

Return:

public truncateSync() source

Override:

Protected Methods

protected async _apply(tx: Transaction): Promise source

Override:

Params:

Return:

protected async _commitBackend(): Promise<boolean> source

Override:

Return:

protected async _commitInternal(tx: Transaction): Promise source

Override:

Params:

Return:

protected _isCommittable(tx: Transaction): boolean source

Override:

Params:

Return:

protected inherit(tx: Transaction): * source

Params:

Return:

public async put(key: , value: ): Promise source

public putSync(key: , value: ) source