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/*
* Copyright 2015 Google Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.datastore.v1.client;
import com.google.datastore.v1.PartitionId;
import com.google.datastore.v1.Query;
import java.util.List;
/**
* Provides the ability to split a query into multiple shards.
*/
public interface QuerySplitter {
/**
* Returns a list of sharded {@link Query}s 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.
*
* @param query the query to split.
* @param partition the partition the query is running in.
* @param numSplits the desired number of splits.
* @param datastore the datastore to run on.
* @throws DatastoreException if there was a datastore error while generating query splits.
* @throws IllegalArgumentException if the given query or numSplits was invalid.
*/
List getSplits(Query query, PartitionId partition, int numSplits, Datastore datastore)
throws DatastoreException;
}