Package com.google.cloud.datastore

Interface DatastoreReader

All Known Subinterfaces:

Datastore, DatastoreReaderWriter, Transaction

@InternalExtensionOnly
public interface DatastoreReader

An interface to represent Google Cloud Datastore read operations.

Method Summary

Modifier and Type	Method	Description
List<Entity>	fetch(Key... keys)	Returns a list with a value for each given key (ordered by input).
Entity	get(Key key)	Returns an Entity for the given Key or null if it doesn't exist.
Iterator<Entity>	get(Key... keys)	Returns an Entity for each given Key that exists in the Datastore.
<T> QueryResults<T>	run(Query<T> query)	Submits a Query and returns its result.
AggregationResults	runAggregation(AggregationQuery query)	Submits a AggregationQuery and returns AggregationResults.
AggregationResults	runAggregation(AggregationQuery query, ExplainOptions explainOptions)	Submits a AggregationQuery with a specified ExplainOptions and returns AggregationResults.

Method Details

get

Entity get(Key key)

Returns an Entity for the given Key or null if it doesn't exist.

Throws:

DatastoreException - upon failure

get

Iterator<Entity> get(Key... keys)

Returns an Entity for each given Key that exists in the Datastore. The order of the result is unspecified. Results are loaded lazily, so it is possible to get a DatastoreException from the returned Iterator's hasNext or next methods.

Throws:

DatastoreException - upon failure

See Also:

• get(Key)

fetch

List<Entity> fetch(Key... keys)

Returns a list with a value for each given key (ordered by input). null values are returned for nonexistent keys. When possible prefer using get(Key...) to avoid eagerly loading the results.

run

<T> QueryResults<T> run(Query<T> query)

Submits a Query and returns its result.

Throws:

DatastoreException - upon failure

runAggregation

AggregationResults runAggregation(AggregationQuery query)

Submits a AggregationQuery and returns AggregationResults.

Throws:

DatastoreException - upon failure

runAggregation

@BetaApi
AggregationResults runAggregation(AggregationQuery query,
 ExplainOptions explainOptions)

Submits a AggregationQuery with a specified ExplainOptions and returns AggregationResults.

Throws:

DatastoreException - upon failure