/***********************************************************************************************************************
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* 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 eu.stratosphere.api.common.functions;
import java.util.Iterator;
import eu.stratosphere.util.Collector;
/**
*
* @param <T> Incoming types
* @param <O> Outgoing types
*/
public interface GenericGroupReduce<T, O> extends Function {
/**
*
* The central function to be implemented for a reducer. The function receives per call one
* key and all the values that belong to that key. Each key is guaranteed to be processed by exactly
* one function call across all involved instances across all computing nodes.
*
* @param records All records that belong to the given input key.
* @param out The collector to hand results to.
* @throws Exception
*/
void reduce(Iterator<T> records, Collector<O> out) throws Exception;
}