AggregateStream.java

/*
 *
 *  * Copyright (c) 2011-2015 EPFL DATA Laboratory
 *  * Copyright (c) 2014-2015 The Squall Collaboration (see NOTICE)
 *  *
 *  * 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 ch.epfl.data.squall.operators;

import java.util.List;

public interface AggregateStream {

    /**
     * <p>
     * Process input tuple and output the update tuples as a result
     * If the withMultiplicty flag is enabled, the update tuples must contain the multiplicity field.
     * Otherwise, the update tuple's value is the delta change.
     * </p>
     * <p>
     *     Example:
     *     Current tuple in the storage: (4, 5, 2) with groupByColumns: (0, 1).
     *     When there is a new incoming tuple and after processing, the map becomes (4, 5, 5).
     *     The output is:
     *     <ul>
     *         <li>
     *             withMultiplicity: (4, 5, 2, -1), (4, 5, 5, 1)
     *         </li>
     *         <li>
     *             without multiplicity: (4, 5, 3)
     *         </li>
     *     </ul>
     * </p>
     * @param tuple
     * @param withMultiplicity
     * @return
     */
    public List<List<String>> updateStream(List<String> tuple, boolean withMultiplicity);

}