/**
* Copyright (C) 2014-2016 LinkedIn Corp. (pinot-core@linkedin.com)
*
* 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.linkedin.pinot.core.query.aggregation;
import com.linkedin.pinot.core.operator.blocks.TransformBlock;
import java.util.List;
/**
* Interface for Aggregation executor, that executes all aggregation
* functions (without group-bys). Aggregations are performed within a segment,
* i.e. does not merge aggregation results from across different segments.
*/
public interface AggregationExecutor {
/**
* Initializations that need to be performed before process can be called.
* Must be called before any of the other methods can be called.
*/
void init();
/**
* Performs the actual aggregation on the given docId's of a segment.
* Asserts that 'init' has been called before calling this method.
*
* @param transformBlock Block on which to perform aggregation.
*/
void aggregate(TransformBlock transformBlock);
/**
* Post processing (if any) to be done after all docIdSets have been processed, and
* before getResult can be called.
* Must be called after all 'aggregation' calls are completed, and before 'getResult'.
* Implementation to make sure that not calling it does not leak resources.
*/
void finish();
/**
* Returns the result of aggregation.
* Asserts that 'finish' has been called before calling getResult().
*
* @return Result of aggregation
*/
List<Object> getResult();
}