com.google.cloud.dataflow.sdk.io.datastore

Class DatastoreV1.Read

java.lang.Object

com.google.cloud.dataflow.sdk.transforms.PTransform<PBegin,PCollection<com.google.datastore.v1.Entity>>

com.google.cloud.dataflow.sdk.io.datastore.DatastoreV1.Read

All Implemented Interfaces:

HasDisplayData, Serializable

Enclosing class:

DatastoreV1

public static class DatastoreV1.Read
extends PTransform<PBegin,PCollection<com.google.datastore.v1.Entity>>

A PTransform that reads the result rows of a Cloud atastore query as Entity objects.

See Also:

DatastoreIO, Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	NUM_QUERY_SPLITS_MAX An upper bound on the number of splits for a query.

Fields inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

name

Method Summary

Modifier and Type	Method and Description
PCollection<com.google.datastore.v1.Entity>	apply(PBegin input) Applies this PTransform on the given InputT, and returns its Output.
String	getNamespace()
String	getProjectId()
com.google.datastore.v1.Query	getQuery()
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
String	toString()
void	validate(PBegin input) Called before invoking apply (which may be intercepted by the runner) to verify this transform is fully specified and applicable to the specified input.
DatastoreV1.Read	withNamespace(String namespace) Returns a new DatastoreV1.Read that reads from the given namespace.
DatastoreV1.Read	withNumQuerySplits(int numQuerySplits) Returns a new DatastoreV1.Read that reads by splitting the given query into numQuerySplits.
DatastoreV1.Read	withProjectId(String projectId) Returns a new DatastoreV1.Read that reads from the Cloud Datastore for the specified project.
DatastoreV1.Read	withQuery(com.google.datastore.v1.Query query) Returns a new DatastoreV1.Read that reads the results of the specified query.

Methods inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

NUM_QUERY_SPLITS_MAX

public static final int NUM_QUERY_SPLITS_MAX

An upper bound on the number of splits for a query.

See Also:

Constant Field Values

Method Detail

withProjectId

public DatastoreV1.Read withProjectId(String projectId)

Returns a new DatastoreV1.Read that reads from the Cloud Datastore for the specified project.

withQuery

public DatastoreV1.Read withQuery(com.google.datastore.v1.Query query)

Returns a new DatastoreV1.Read that reads the results of the specified query.

Note: Normally, DatastoreIO will read from Cloud Datastore in parallel across many workers. However, when the Query is configured with a limit using Query.Builder#setLimit, then all results will be read by a single worker in order to ensure correct results.

withNamespace

public DatastoreV1.Read withNamespace(String namespace)

Returns a new DatastoreV1.Read that reads from the given namespace.

withNumQuerySplits

public DatastoreV1.Read withNumQuerySplits(int numQuerySplits)

Returns a new DatastoreV1.Read that reads by splitting the given query into numQuerySplits.

The semantics for the query splitting is defined below:

• Any value less than or equal to 0 will be ignored, and the number of splits will be chosen dynamically at runtime based on the query data size.
• Any value greater than NUM_QUERY_SPLITS_MAX will be capped at NUM_QUERY_SPLITS_MAX.
• If the query has a user limit set, then numQuerySplits will be ignored and no split will be performed.
• Under certain cases Cloud Datastore is unable to split query to the requested number of splits. In such cases we just use whatever the Datastore returns.

getQuery

@Nullable
public com.google.datastore.v1.Query getQuery()

getProjectId

@Nullable
public String getProjectId()

getNamespace

@Nullable
public String getNamespace()

apply

public PCollection<com.google.datastore.v1.Entity> apply(PBegin input)

Applies this PTransform on the given InputT, and returns its Output.

Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

The default implementation throws an exception. A derived class must either implement apply, or else each runner must supply a custom implementation via PipelineRunner.apply(com.google.cloud.dataflow.sdk.transforms.PTransform<InputT, OutputT>, InputT).

Overrides:

apply in class PTransform<PBegin,PCollection<com.google.datastore.v1.Entity>>

validate

public void validate(PBegin input)

Description copied from class: PTransform

Called before invoking apply (which may be intercepted by the runner) to verify this transform is fully specified and applicable to the specified input.

By default, does nothing.

Overrides:

validate in class PTransform<PBegin,PCollection<com.google.datastore.v1.Entity>>

populateDisplayData

public void populateDisplayData(DisplayData.Builder builder)

Description copied from class: PTransform

Register display data for the given transform or component.

populateDisplayData(DisplayData.Builder) is invoked by Pipeline runners to collect display data via DisplayData.from(HasDisplayData). Implementations may call super.populateDisplayData(builder) in order to register display data in the current namespace, but should otherwise use subcomponent.populateDisplayData(builder) to use the namespace of the subcomponent.

By default, does not register any display data. Implementors may override this method to provide their own display data.

Specified by:

populateDisplayData in interface HasDisplayData

Overrides:

populateDisplayData in class PTransform<PBegin,PCollection<com.google.datastore.v1.Entity>>

Parameters:

builder - The builder to populate with display data.

See Also:

HasDisplayData

toString

public String toString()

Overrides:

toString in class PTransform<PBegin,PCollection<com.google.datastore.v1.Entity>>