io.datakernel.aggregation.Aggregate Maven / Gradle / Ivy
/*
* Copyright (C) 2015 SoftIndex LLC.
*
* 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 io.datakernel.aggregation;
/**
* Accumulates records using arithmetic summation.
*/
public interface Aggregate {
/**
* Creates an object which holds arithmetic sum of accumulated records.
*
* @param record record whose fields are to be accumulated
* @return accumulator object
*/
Object createAccumulator(Object record);
/**
* Performs the following operation: accumulator = accumulator + record.
*
* @param accumulator accumulator which holds the current sum of records
* @param record record to add to the accumulator
*/
void accumulate(Object accumulator, Object record);
}