Interface Datastore (2.21.2) 

public interface Datastore extends Service<DatastoreOptions>, DatastoreReaderWriter

An interface for Google Cloud Datastore.

Implements

com.google.cloud.Service<com.google.cloud.datastore.DatastoreOptions>, DatastoreReaderWriter

Methods

<T>run(Query<T> query, ReadOption[] options)

public abstract QueryResults<T> <T>run(Query<T> query, ReadOption[] options)

Submits a Query and returns its result. ReadOptions can be specified if desired.

Example of running a query to find all entities of one kind.


 String kind = "my_kind";
 StructuredQuery<Entity> query = Query.newEntityQueryBuilder()
     .setKind(kind)
     .build();
 QueryResults<Entity> results = datastore.run(query);
 List<Entity> entities = Lists.newArrayList();
 while (results.hasNext()) {
   Entity result = results.next();
   // do something with result
   entities.add(result);
 }

Example of running a query to find all entities with a matching property value.


 String kind = "my_kind";
 String property = "my_property";
 String value = "my_value";
 StructuredQuery<Entity> query = Query.newEntityQueryBuilder()
     .setKind(kind)
     .setFilter(PropertyFilter.eq(property, value))
     .build();
 QueryResults<Entity> results = datastore.run(query);
 List<Entity> entities = Lists.newArrayList();
 while (results.hasNext()) {
   Entity result = results.next();
   // do something with result
   entities.add(result);
 }
Parameters
Name Description
query Query<T>
options ReadOption[]
Returns
Type Description
QueryResults<T>

<T>run(Query<T> query, ExplainOptions explainOptions, ReadOption[] options)

public default QueryResults<T> <T>run(Query<T> query, ExplainOptions explainOptions, ReadOption[] options)

Submits a Query with specified com.google.cloud.datastore.models.ExplainOptions and returns its result. ReadOptions can be specified if desired.

Example of running a query to find all entities of one kind.


 String kind = "my_kind";
 StructuredQuery<Entity> query = Query.newEntityQueryBuilder()
     .setKind(kind)
     .build();
 QueryResults<Entity> results = datastore.run(query, ExplainOptions.newBuilder().setAnalyze(true).build());
Parameters
Name Description
query Query<T>
explainOptions ExplainOptions
options ReadOption[]
Returns
Type Description
QueryResults<T>

<T>runInTransaction(Datastore.TransactionCallable<T> callable)

public abstract T <T>runInTransaction(Datastore.TransactionCallable<T> callable)

Invokes the callback's Datastore.TransactionCallable#run method with a DatastoreReaderWriter that is associated with a new transaction. The transaction will be committed upon successful invocation. Any thrown exception will cause the transaction to rollback and will be propagated as a DatastoreException with the original exception as its root cause.

Example of running in a transaction.


 String callableResult = "my_callable_result";
 TransactionCallable<String> callable = new TransactionCallable<String>() {
   public String run(DatastoreReaderWriter readerWriter) {
     // use readerWriter to run in transaction
     return callableResult;
   }
 };
 String result = datastore.runInTransaction(callable);
Parameter
Name Description
callable TransactionCallable<T>

the callback to call with a newly created transactional readerWriter
Returns
Type Description
T

<T>runInTransaction(Datastore.TransactionCallable<T> callable, TransactionOptions options)

public abstract T <T>runInTransaction(Datastore.TransactionCallable<T> callable, TransactionOptions options)

Invokes the callback's Datastore.TransactionCallable#run method with a DatastoreReaderWriter that is associated with a new transaction. The transaction will be committed upon successful invocation. Any thrown exception will cause the transaction to rollback and will be propagated as a DatastoreException with the original exception as its root cause. If TransactionOptions is set to read-write mode, previous transaction Id in the options will be automatically populated each time a transaction is retried.

Example of running in a transaction.


 String callableResult = "my_callable_result";
 TransactionCallable<String> callable = new TransactionCallable<String>() {
   public String run(DatastoreReaderWriter readerWriter) {
     // use readerWriter to run in transaction
     return callableResult;
   }
 };

 TransactionOptions options = TransactionOptions.newBuilder()
     .setReadWrite(TransactionOptions.ReadWrite
         .getDefaultInstance())
     .build();

 String result = datastore.runInTransaction(callable, options);
Parameters
Name Description
callable TransactionCallable<T>

the callback to call with a newly created transactional readerWriter
options TransactionOptions

the Transaction options indicating whether the transaction mode is Read-only or Read-Write
Returns
Type Description
T

add(FullEntity<?> entity)

public abstract Entity add(FullEntity<?> entity)

Datastore add operation: inserts the provided entity. This method will automatically allocate an id if necessary.

If an entity for entity.getKey() does not exist, entity is inserted. Otherwise, a DatastoreException is thrown with DatastoreException#getReason() equal to "ALREADY_EXISTS".

Example of adding a single entity.


 String keyName = "my_key_name";
 Key key = datastore.newKeyFactory().setKind("MyKind").newKey(keyName);
 Entity.Builder entityBuilder = Entity.newBuilder(key);
 entityBuilder.set("propertyName", "value");
 Entity entity = entityBuilder.build();
 try {
   datastore.add(entity);
 } catch (DatastoreException ex) {
   if ("ALREADY_EXISTS".equals(ex.getReason())) {
     // entity.getKey() already exists
   }
 }
Parameter
Name Description
entity FullEntity<?>
Returns
Type Description
Entity

add(FullEntity<?>[] entities)

public abstract List<Entity> add(FullEntity<?>[] entities)

Datastore add operation: inserts the provided entities. This method will automatically allocate id for any entity with an incomplete key.

If none of entities' keys exist, all entities are inserted. If any of entities' keys already exists the method throws a DatastoreException with DatastoreException#getReason() equal to "ALREADY_EXISTS". All entities in entities whose key did not exist are inserted. To achieve a transactional behavior, use Transaction.

Example of adding multiple entities.


 String keyName1 = "my_key_name1";
 String keyName2 = "my_key_name2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Entity.Builder entityBuilder1 = Entity.newBuilder(key1);
 entityBuilder1.set("propertyName", "value1");
 Entity entity1 = entityBuilder1.build();

 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Entity.Builder entityBuilder2 = Entity.newBuilder(key2);
 entityBuilder2.set("propertyName", "value2");
 Entity entity2 = entityBuilder2.build();

 try {
   datastore.add(entity1, entity2);
 } catch (DatastoreException ex) {
   if ("ALREADY_EXISTS".equals(ex.getReason())) {
     // at least one of entity1.getKey() and entity2.getKey() already exists
   }
 }
Parameter
Name Description
entities FullEntity<?>[]
Returns
Type Description
List<Entity>

allocateId(IncompleteKey key)

public abstract Key allocateId(IncompleteKey key)

Allocate a unique id for the given key. The returned key will have the same information (projectId, kind, namespace and ancestors) as the given key and will have a newly assigned id.

Example of allocating an id.


 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 IncompleteKey incompleteKey = keyFactory.newKey();

 // let cloud datastore automatically assign an id
 Key key = datastore.allocateId(incompleteKey);
Parameter
Name Description
key IncompleteKey
Returns
Type Description
Key

allocateId(IncompleteKey[] keys)

public abstract List<Key> allocateId(IncompleteKey[] keys)

Returns a list of keys using the allocated ids ordered by the input.

Example of allocating multiple ids in a single batch.


 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 IncompleteKey incompleteKey1 = keyFactory.newKey();
 IncompleteKey incompleteKey2 = keyFactory.newKey();

 // let cloud datastore automatically assign the ids
 List<Key> keys = datastore.allocateId(incompleteKey1, incompleteKey2);

See Also: #allocateId(IncompleteKey)

Parameter
Name Description
keys IncompleteKey[]
Returns
Type Description
List<Key>

delete(Key[] keys)

public abstract void delete(Key[] keys)

A datastore delete operation. It is OK to request the deletion of a non-existing key.

Example of deleting multiple entities.


 String keyName1 = "my_key_name1";
 String keyName2 = "my_key_name2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 datastore.delete(key1, key2);
Parameter
Name Description
keys Key[]

fetch(Iterable<Key> keys, ReadOption[] options)

public abstract List<Entity> fetch(Iterable<Key> keys, ReadOption[] options)

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. ReadOptions can be specified if desired.

Example of fetching a list of Entity objects.


 String firstKeyName = "my_first_key_name";
 String secondKeyName = "my_second_key_name";
 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 Key firstKey = keyFactory.newKey(firstKeyName);
 Key secondKey = keyFactory.newKey(secondKeyName);
 List<Entity> entities = datastore.fetch(Lists.newArrayList(firstKey, secondKey));
 for (Entity entity : entities) {
   // do something with the entity
 }
Parameters
Name Description
keys Iterable<Key>
options ReadOption[]
Returns
Type Description
List<Entity>

get(Key key, ReadOption[] options)

public abstract Entity get(Key key, ReadOption[] options)

Returns an Entity for the given Key or null if it doesn't exist. ReadOptions can be specified if desired.

Example of getting an entity.


 String keyName = "my_key_name";
 Key key = datastore.newKeyFactory().setKind("MyKind").newKey(keyName);
 Entity entity = datastore.get(key);
 // Do something with the entity
Parameters
Name Description
key Key
options ReadOption[]
Returns
Type Description
Entity

get(Iterable<Key> keys, ReadOption[] options)

public abstract Iterator<Entity> get(Iterable<Key> keys, ReadOption[] options)

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. ReadOptions can be specified if desired.

Example of getting multiple entity objects.


 String firstKeyName = "my_first_key_name";
 String secondKeyName = "my_second_key_name";
 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 Key firstKey = keyFactory.newKey(firstKeyName);
 Key secondKey = keyFactory.newKey(secondKeyName);
 Iterator<Entity> entitiesIterator = datastore.get(Lists.newArrayList(firstKey, secondKey));
 List<Entity> entities = Lists.newArrayList();
 while (entitiesIterator.hasNext()) {
   Entity entity = entitiesIterator.next();
   // do something with the entity
   entities.add(entity);
 }

See Also: #get(Key)

Parameters
Name Description
keys Iterable<Key>
options ReadOption[]
Returns
Type Description
Iterator<Entity>

newBatch()

public abstract Batch newBatch()

Returns a new Batch for processing multiple write operations in one request.

Example of starting a new batch.


 String keyName1 = "my_key_name_1";
 String keyName2 = "my_key_name_2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Batch batch = datastore.newBatch();
 Entity entity1 = Entity.newBuilder(key1).set("name", "John").build();
 Entity entity2 = Entity.newBuilder(key2).set("title", "title").build();
 batch.add(entity1);
 batch.add(entity2);
 batch.submit();
Returns
Type Description
Batch

newKeyFactory()

public abstract KeyFactory newKeyFactory()

Returns a new KeyFactory for this service

Example of creating a KeyFactory.


 KeyFactory keyFactory = datastore.newKeyFactory();
Returns
Type Description
KeyFactory

newTransaction()

public abstract Transaction newTransaction()

Returns a new Datastore transaction.

Returns
Type Description
Transaction

newTransaction(TransactionOptions options)

public abstract Transaction newTransaction(TransactionOptions options)

Returns a new Datastore transaction.

Parameter
Name Description
options TransactionOptions

a transaction option indicating the mode of the transaction (read-only or read-write)
Returns
Type Description
Transaction

put(FullEntity<?> entity)

public abstract Entity put(FullEntity<?> entity)

A Datastore put (a.k.a upsert) operation: inserts an entity if it does not exist, updates it otherwise. This method will automatically allocate an id if necessary.

Example of putting a single entity.


 String keyName = "my_key_name";
 Key key = datastore.newKeyFactory().setKind("MyKind").newKey(keyName);
 Entity.Builder entityBuilder = Entity.newBuilder(key);
 entityBuilder.set("propertyName", "value");
 Entity entity = entityBuilder.build();
 datastore.put(entity);
Parameter
Name Description
entity FullEntity<?>
Returns
Type Description
Entity

put(FullEntity<?>[] entities)

public abstract List<Entity> put(FullEntity<?>[] entities)

A Datastore put (a.k.a upsert) operation: creates an entity if it does not exist, updates it otherwise. This method will automatically allocate id for any entity with an incomplete key.

Example of putting multiple entities.


 String keyName1 = "my_key_name1";
 String keyName2 = "my_key_name2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Entity.Builder entityBuilder1 = Entity.newBuilder(key1);
 entityBuilder1.set("propertyName", "value1");
 Entity entity1 = entityBuilder1.build();

 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Entity.Builder entityBuilder2 = Entity.newBuilder(key2);
 entityBuilder2.set("propertyName", "value2");
 Entity entity2 = entityBuilder2.build();

 datastore.put(entity1, entity2);
Parameter
Name Description
entities FullEntity<?>[]
Returns
Type Description
List<Entity>

reserveIds(Key[] keys)

public abstract List<Key> reserveIds(Key[] keys)

Reserve one or more keys, preventing them from being automatically allocated by Datastore.

Example of reserving multiple ids in a single batch.


 KeyFactory keyFactory = datastore.newKeyFactory().setKind("MyKind");
 Key key1 = keyFactory.newKey(10);
 Key key2 = keyFactory.newKey("name");
 List<Key> keys = datastore.reserveIds(key1, key2);
Parameter
Name Description
keys Key[]
Returns
Type Description
List<Key>

runAggregation(AggregationQuery query, ReadOption[] options)

public default AggregationResults runAggregation(AggregationQuery query, ReadOption[] options)

Submits a AggregationQuery and returns AggregationResults. ReadOptions can be specified if desired.

Example of running an AggregationQuery to find the count of entities of one kind.

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);
 for (AggregationResult aggregationResult : aggregationResults) {
     System.out.println(aggregationResult.get("total_count"));
 }

GqlQuery example:


 GqlQuery selectAllGqlQuery = Query.newGqlQueryBuilder(
         "AGGREGATE COUNT(*) AS total_count, COUNT_UP_TO(100) AS count_upto_100 OVER(SELECT * FROM Task)"
     )
     .setAllowLiteral(true)
     .build();
 AggregationQuery aggregationQuery = Query.newAggregationQueryBuilder()
     .over(selectAllGqlQuery)
     .build();
 AggregationResults aggregationResults = datastore.runAggregation(aggregationQuery);
 for (AggregationResult aggregationResult : aggregationResults) {
   System.out.println(aggregationResult.get("total_count"));
   System.out.println(aggregationResult.get("count_upto_100"));
 }
Parameters
Name Description
query AggregationQuery
options ReadOption[]
Returns
Type Description
AggregationResults AggregationResults

runAggregation(AggregationQuery query, ExplainOptions explainOptions, ReadOption[] options)

public default AggregationResults runAggregation(AggregationQuery query, ExplainOptions explainOptions, ReadOption[] options)

Submits a AggregationQuery with specified com.google.cloud.datastore.models.ExplainOptions and returns AggregationResults. ReadOptions can be specified if desired.

Example of running an AggregationQuery to find the count of entities of one kind.

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, ExplainOptions.newBuilder().setAnalyze(true).build());
Parameters
Name Description
query AggregationQuery
explainOptions ExplainOptions
options ReadOption[]
Returns
Type Description
AggregationResults AggregationResults

update(Entity[] entities)

public abstract void update(Entity[] entities)

A Datastore update operation. The operation will fail if an entity with the same key does not already exist.

Example of updating multiple entities.


 String keyName1 = "my_key_name_1";
 String keyName2 = "my_key_name_2";
 Key key1 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName1);
 Entity.Builder entityBuilder1 = Entity.newBuilder(key1);
 entityBuilder1.set("propertyName", "updatedValue1");
 Entity entity1 = entityBuilder1.build();

 Key key2 = datastore.newKeyFactory().setKind("MyKind").newKey(keyName2);
 Entity.Builder entityBuilder2 = Entity.newBuilder(key2);
 entityBuilder2.set("propertyName", "updatedValue2");
 Entity entity2 = entityBuilder2.build();

 datastore.update(entity1, entity2);
Parameter
Name Description
entities Entity[]