com.google.cloud.datastore

Class Query<V>

java.lang.Object

com.google.cloud.datastore.Query<V>

Type Parameters:

V - the type of the values returned by this query.

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

AggregationQuery, GqlQuery, StructuredQuery

public abstract class Query<V>
extends Object
implements Serializable

A Google Cloud Datastore query. For usage examples see GqlQuery, StructuredQuery and AggregationQuery.

Note that queries require proper indexing. See Cloud Datastore Index Configuration for help configuring indexes.

See Also:

Datastore Queries, Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Query.ResultType<V> This class represents the expected type of the result.

Method Summary

Modifier and Type	Method and Description
String	getNamespace()
static AggregationQuery.Builder	newAggregationQueryBuilder() Returns a new AggregationQuery builder.
static EntityQuery.Builder	newEntityQueryBuilder() Returns a new StructuredQuery builder for full (complete entities) queries.
static <V> GqlQuery.Builder<V>	newGqlQueryBuilder(Query.ResultType<V> resultType, String gql) Returns a new GqlQuery builder.
static GqlQuery.Builder<?>	newGqlQueryBuilder(String gql) Returns a new GqlQuery builder.
static KeyQuery.Builder	newKeyQueryBuilder() Returns a new StructuredQuery builder for key only queries.
static ProjectionEntityQuery.Builder	newProjectionEntityQueryBuilder() Returns a new StructuredQuery builder for projection queries.

Methods inherited from class java.lang.Object

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

Method Detail

getNamespace

public String getNamespace()

newGqlQueryBuilder

public static GqlQuery.Builder<?> newGqlQueryBuilder(String gql)

Returns a new GqlQuery builder.

Example of creating and running a GQL query.

 String kind = "my_kind";
 String gqlQuery = "select * from " + kind;
 Query<?> query = Query.newGqlQueryBuilder(gqlQuery).build();
 QueryResults<?> results = datastore.run(query);
 // Use results
 

See Also:

GQL Reference

newGqlQueryBuilder

public static <V> GqlQuery.Builder<V> newGqlQueryBuilder(Query.ResultType<V> resultType,
                                                         String gql)

Returns a new GqlQuery builder.

Example of creating and running a typed GQL query.

 String kind = "my_kind";
 String gqlQuery = "select * from " + kind;
 Query<Entity> query = Query.newGqlQueryBuilder(Query.ResultType.ENTITY, gqlQuery).build();
 QueryResults<Entity> results = datastore.run(query);
 // Use results
 

See Also:

GQL Reference

newEntityQueryBuilder

public static EntityQuery.Builder newEntityQueryBuilder()

Returns a new StructuredQuery builder for full (complete entities) queries.

Example of creating and running an entity query.

 String kind = "my_kind";
 Query<Entity> query = Query.newEntityQueryBuilder().setKind(kind).build();
 QueryResults<Entity> results = datastore.run(query);
 // Use results
 

newKeyQueryBuilder

public static KeyQuery.Builder newKeyQueryBuilder()

Returns a new StructuredQuery builder for key only queries.

Example of creating and running a key query.

 String kind = "my_kind";
 Query<Key> query = Query.newKeyQueryBuilder().setKind(kind).build();
 QueryResults<Key> results = datastore.run(query);
 // Use results
 

newProjectionEntityQueryBuilder

public static ProjectionEntityQuery.Builder newProjectionEntityQueryBuilder()

Returns a new StructuredQuery builder for projection queries.

Example of creating and running a projection entity query.

 String kind = "my_kind";
 String property = "my_property";
 Query<ProjectionEntity> query = Query.newProjectionEntityQueryBuilder()
     .setKind(kind)
     .addProjection(property)
     .build();
 QueryResults<ProjectionEntity> results = datastore.run(query);
 // Use results
 

newAggregationQueryBuilder

public static AggregationQuery.Builder newAggregationQueryBuilder()

Returns a new AggregationQuery builder.

Example of creating and running an AggregationQuery.

StructuredQuery example:

 EntityQuery selectAllQuery = Query.newEntityQueryBuilder()
    .setKind("Task")
    .build();
 AggregationQuery aggregationQuery = Query.newAggregationQueryBuilder()
    .addAggregation(count().as("total_count"))
    .over(selectAllQuery)
    .build();
 AggregationResults aggregationResults = datastore.runAggregation(aggregationQuery);
 // Use aggregationResults
 

GqlQuery example:

 GqlQuery<?> selectAllGqlQuery = Query.newGqlQueryBuilder(
         "AGGREGATE COUNT(*) AS total_count OVER(SELECT * FROM Task)"
     )
     .setAllowLiteral(true)
     .build();
 AggregationQuery aggregationQuery = Query.newAggregationQueryBuilder()
     .over(selectAllGqlQuery)
     .build();
 AggregationResults aggregationResults = datastore.runAggregation(aggregationQuery);
 // Use aggregationResults