com.google.datastore.v1.client

Interface QuerySplitter

public interface QuerySplitter

Provides the ability to split a query into multiple shards.

Method Summary

Modifier and Type	Method and Description
List<Query>	getSplits(Query query, PartitionId partition, int numSplits, Datastore datastore) Returns a list of sharded Querys for the given query.
default List<Query>	getSplits(Query query, PartitionId partition, int numSplits, Datastore datastore, com.google.protobuf.Timestamp readTime) Same as getSplits(Query, PartitionId, int, Datastore) but the splits are based on readTime, and the returned sharded Querys should also be executed with readTime.

Method Detail

getSplits

List<Query> getSplits(Query query,
                      PartitionId partition,
                      int numSplits,
                      Datastore datastore)
               throws DatastoreException

Returns a list of sharded Querys for the given query.

This will create up to the desired number of splits, however it may return less splits if the desired number of splits is unavailable. This will happen if the number of split points provided by the underlying Datastore is less than the desired number, which will occur if the number of results for the query is too small.

Parameters:

query - the query to split.

partition - the partition the query is running in.

numSplits - the desired number of splits.

datastore - the datastore to run on.

Throws:

DatastoreException - if there was a datastore error while generating query splits.

IllegalArgumentException - if the given query or numSplits was invalid.

getSplits

@BetaApi
default List<Query> getSplits(Query query,
                                       PartitionId partition,
                                       int numSplits,
                                       Datastore datastore,
                                       com.google.protobuf.Timestamp readTime)
                                throws DatastoreException

Same as getSplits(Query, PartitionId, int, Datastore) but the splits are based on readTime, and the returned sharded Querys should also be executed with readTime. Reading from a timestamp is currently a private preview feature in Datastore.

Throws:

DatastoreException