org.apache.beam.sdk.io.gcp.datastore

Class DatastoreV1.Read

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PBegin,PCollection<Entity>>

org.apache.beam.sdk.io.gcp.datastore.DatastoreV1.Read

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

Enclosing class:

DatastoreV1

public abstract static class DatastoreV1.Read
extends PTransform<PBegin,PCollection<Entity>>

A PTransform that reads the result rows of a Cloud Datastore 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 org.apache.beam.sdk.transforms.PTransform

name, resourceHints

Constructor Summary

Constructors

Constructor and Description
Read()

Method Summary

Modifier and Type	Method and Description
PCollection<Entity>	expand(PBegin input) Override this method to specify how this PTransform should be expanded on the given InputT.
abstract @Nullable ValueProvider<java.lang.String>	getLiteralGqlQuery()
abstract @Nullable java.lang.String	getLocalhost()
abstract @Nullable ValueProvider<java.lang.String>	getNamespace()
long	getNumEntities(PipelineOptions options, java.lang.String ourKind, @Nullable java.lang.String namespace) Returns Number of entities available for reading.
abstract int	getNumQuerySplits()
abstract @Nullable ValueProvider<java.lang.String>	getProjectId()
abstract @Nullable Query	getQuery()
abstract @Nullable Instant	getReadTime()
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
abstract java.lang.String	toString()
DatastoreV1.Read	withLiteralGqlQuery(java.lang.String gqlQuery) Returns a new DatastoreV1.Read that reads the results of the specified GQL query.
DatastoreV1.Read	withLiteralGqlQuery(ValueProvider<java.lang.String> gqlQuery) Same as withLiteralGqlQuery(String) but with a ValueProvider.
DatastoreV1.Read	withLocalhost(java.lang.String localhost) Returns a new DatastoreV1.Read that reads from a Datastore Emulator running at the given localhost address.
DatastoreV1.Read	withNamespace(java.lang.String namespace) Returns a new DatastoreV1.Read that reads from the given namespace.
DatastoreV1.Read	withNamespace(ValueProvider<java.lang.String> namespace) Same as withNamespace(String) but with a ValueProvider.
DatastoreV1.Read	withNumQuerySplits(int numQuerySplits) Returns a new DatastoreV1.Read that reads by splitting the given query into numQuerySplits.
DatastoreV1.Read	withProjectId(java.lang.String projectId) Returns a new DatastoreV1.Read that reads from the Cloud Datastore for the specified project.
DatastoreV1.Read	withProjectId(ValueProvider<java.lang.String> projectId) Same as withProjectId(String) but with a ValueProvider.
DatastoreV1.Read	withQuery(Query query) Returns a new DatastoreV1.Read that reads the results of the specified query.
DatastoreV1.Read	withReadTime(Instant readTime) Returns a new DatastoreV1.Read that reads at the specified readTime.

Methods inherited from class org.apache.beam.sdk.transforms.PTransform

compose, compose, getAdditionalInputs, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, getResourceHints, setResourceHints, validate

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

Constructor Detail

Read

public Read()

Method Detail

getProjectId

public abstract @Nullable ValueProvider<java.lang.String> getProjectId()

getQuery

public abstract @Nullable Query getQuery()

getLiteralGqlQuery

public abstract @Nullable ValueProvider<java.lang.String> getLiteralGqlQuery()

getNamespace

public abstract @Nullable ValueProvider<java.lang.String> getNamespace()

getNumQuerySplits

public abstract int getNumQuerySplits()

getLocalhost

public abstract @Nullable java.lang.String getLocalhost()

getReadTime

public abstract @Nullable Instant getReadTime()

toString

public abstract java.lang.String toString()

Overrides:

toString in class PTransform<PBegin,PCollection<Entity>>

withProjectId

public DatastoreV1.Read withProjectId(java.lang.String projectId)

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

withProjectId

public DatastoreV1.Read withProjectId(ValueProvider<java.lang.String> projectId)

Same as withProjectId(String) but with a ValueProvider.

withQuery

public DatastoreV1.Read withQuery(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.

withLiteralGqlQuery

public DatastoreV1.Read withLiteralGqlQuery(java.lang.String gqlQuery)

Returns a new DatastoreV1.Read that reads the results of the specified GQL query. See GQL Reference to know more about GQL grammar.

Note: This query is executed with literals allowed, so the users should ensure that the query is originated from trusted sources to avoid any security vulnerabilities via SQL Injection.

Cloud Datastore does not a provide a clean way to translate a gql query string to Query, so we end up making a query to the service for translation but this may read the actual data, although it will be a small amount. It needs more validation through production use cases before marking it as stable.

withLiteralGqlQuery

public DatastoreV1.Read withLiteralGqlQuery(ValueProvider<java.lang.String> gqlQuery)

Same as withLiteralGqlQuery(String) but with a ValueProvider.

withNamespace

public DatastoreV1.Read withNamespace(java.lang.String namespace)

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

withNamespace

public DatastoreV1.Read withNamespace(ValueProvider<java.lang.String> namespace)

Same as withNamespace(String) but with a ValueProvider.

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 Cloud Datastore returns.

withLocalhost

public DatastoreV1.Read withLocalhost(java.lang.String localhost)

Returns a new DatastoreV1.Read that reads from a Datastore Emulator running at the given localhost address.

withReadTime

public DatastoreV1.Read withReadTime(Instant readTime)

Returns a new DatastoreV1.Read that reads at the specified readTime.

getNumEntities

public long getNumEntities(PipelineOptions options,
                           java.lang.String ourKind,
                           @Nullable java.lang.String namespace)

Returns Number of entities available for reading.

expand

public PCollection<Entity> expand(PBegin input)

Description copied from class: PTransform

Override this method to specify how this PTransform should be expanded on the given InputT.

NOTE: This method should not be called directly. Instead apply the PTransform should be applied to the InputT using the apply method.

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).

Specified by:

expand in class PTransform<PBegin,PCollection<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<Entity>>

Parameters:

builder - The builder to populate with display data.

See Also:

HasDisplayData