public class DatastoreV1
extends java.lang.Object
DatastoreV1 provides an API to Read, Write and Delete PCollections of
Google Cloud Datastore version v1 Entity objects. Read is only supported for Bounded PCollections while Write and Delete are
supported for both Bounded and Unbounded PCollections.
This API currently requires an authentication workaround. To use DatastoreV1, users
must use the gcloud command line tool to get credentials for Cloud Datastore:
$ gcloud auth login
To read a PCollection from a query to Cloud Datastore, use read()
and its methods DatastoreV1.Read.withProjectId(java.lang.String) and DatastoreV1.Read.withQuery(com.google.datastore.v1.Query) to
specify the project to query and the query to read from. You can optionally provide a namespace
to query within using DatastoreV1.Read.withNamespace(java.lang.String). You could also optionally specify
how many splits you want for the query using DatastoreV1.Read.withNumQuerySplits(int).
For example:
// Read a query from Datastore
PipelineOptions options = PipelineOptionsFactory.fromArgs(args).create();
Query query = ...;
String projectId = "...";
Pipeline p = Pipeline.create(options);
PCollection<Entity> entities = p.apply(
DatastoreIO.v1().read()
.withProjectId(projectId)
.withQuery(query));
Note: A runner may read from Cloud Datastore in parallel across many workers. However,
when the Query is configured with a limit using Query.Builder.setLimit(Int32Value) or if the Query contains inequality
filters like GREATER_THAN, LESS_THAN etc., then all returned results will be read by a
single worker in order to ensure correct data. Since data is read from a single worker, this
could have a significant impact on the performance of the job.
To write a PCollection to a Cloud Datastore, use write(), specifying
the Cloud Datastore project to write to:
PCollection<Entity> entities = ...;
entities.apply(DatastoreIO.v1().write().withProjectId(projectId));
p.run();
To delete a PCollection of Entities from Cloud Datastore, use deleteEntity(), specifying the Cloud Datastore project to write to:
PCollection<Entity> entities = ...;
entities.apply(DatastoreIO.v1().deleteEntity().withProjectId(projectId));
p.run();
To delete entities associated with a PCollection of Keys from Cloud
Datastore, use deleteKey(), specifying the Cloud Datastore project to write to:
PCollection<Entity> entities = ...;
entities.apply(DatastoreIO.v1().deleteKey().withProjectId(projectId));
p.run();
Write and delete operations will follow a gradual ramp-up by default in order to protect Cloud
Datastore from potential overload. This rate limit follows a heuristic based on the expected
number of workers. To optimize throughput in this initial stage, you can provide a hint to the
relevant PTransform by calling withHintNumWorkers, e.g., DatastoreIO.v1().deleteKey().withHintNumWorkers(numWorkers). While not recommended, you can also
turn this off via .withRampupThrottlingDisabled().
Entities in the PCollection to be written or deleted must have complete
Keys. Complete Keys specify the name and id of the Entity, where incomplete Keys do not. A namespace other than projectId
default may be used by specifying it in the Entity Keys.
Key.Builder keyBuilder = DatastoreHelper.makeKey(...);
keyBuilder.getPartitionIdBuilder().setNamespace(namespace);
Entities will be committed as upsert (update or insert) or delete mutations. Please
read Entities, Properties,
and Keys for more information about Entity keys.
PipelineRunner that is used to execute the
pipeline. Please refer to the documentation of corresponding PipelineRunners for more
details.
Please see Cloud Datastore Sign Up for security and permission related information specific to Cloud Datastore.
Optionally, Cloud Datastore V1 Emulator, running locally, could be used for testing purposes
by providing the host port information through withLocalhost("host:port" for all the
above transforms. In such a case, all the Cloud Datastore API calls are directed to the Emulator.
| Modifier and Type | Class and Description |
|---|---|
static class |
DatastoreV1.DeleteEntity
A
PTransform that deletes Entities from Cloud Datastore. |
static class |
DatastoreV1.DeleteKey
|
static class |
DatastoreV1.Read
A
PTransform that reads the result rows of a Cloud Datastore query as Entity
objects. |
static class |
DatastoreV1.Write
A
PTransform that writes Entity objects to Cloud Datastore. |
| Modifier and Type | Method and Description |
|---|---|
DatastoreV1.DeleteEntity |
deleteEntity()
Returns an empty
DatastoreV1.DeleteEntity builder. |
DatastoreV1.DeleteKey |
deleteKey()
Returns an empty
DatastoreV1.DeleteKey builder. |
DatastoreV1.Read |
read()
Returns an empty
DatastoreV1.Read builder. |
DatastoreV1.Write |
write()
Returns an empty
DatastoreV1.Write builder. |
public DatastoreV1.Read read()
DatastoreV1.Read builder. Configure the source projectId,
query, and optionally namespace and numQuerySplits using DatastoreV1.Read.withProjectId(java.lang.String), DatastoreV1.Read.withQuery(com.google.datastore.v1.Query), DatastoreV1.Read.withNamespace(java.lang.String), DatastoreV1.Read.withNumQuerySplits(int).public DatastoreV1.Write write()
DatastoreV1.Write builder. Configure the destination projectId
using DatastoreV1.Write.withProjectId(java.lang.String).public DatastoreV1.DeleteEntity deleteEntity()
DatastoreV1.DeleteEntity builder. Configure the destination projectId
using DatastoreV1.DeleteEntity.withProjectId(java.lang.String).public DatastoreV1.DeleteKey deleteKey()
DatastoreV1.DeleteKey builder. Configure the destination projectId using
DatastoreV1.DeleteKey.withProjectId(java.lang.String).