algebricks/algebricks-runtime/src/main/java/edu/uci/ics/hyracks/algebricks/runtime/aggregators/TupleCountRunningAggregateFunctionFactory.java

/*
 * Copyright 2009-2010 by The Regents of the University of California
 * 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 from
 * 
 *     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 edu.uci.ics.hyracks.algebricks.runtime.aggregators;

import java.io.IOException;

import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.runtime.base.IRunningAggregateEvaluator;
import edu.uci.ics.hyracks.algebricks.runtime.base.IRunningAggregateEvaluatorFactory;
import edu.uci.ics.hyracks.data.std.api.IPointable;
import edu.uci.ics.hyracks.data.std.util.ArrayBackedValueStorage;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.IFrameTupleReference;

public class TupleCountRunningAggregateFunctionFactory implements IRunningAggregateEvaluatorFactory {

    private static final long serialVersionUID = 1L;

    @Override
    public IRunningAggregateEvaluator createRunningAggregateEvaluator() throws AlgebricksException {
        final ArrayBackedValueStorage abvs = new ArrayBackedValueStorage();
        return new IRunningAggregateEvaluator() {

            int cnt;

            @Override
            public void step(IFrameTupleReference tuple, IPointable result) throws AlgebricksException {
                ++cnt;
                try {
                    abvs.reset();
                    abvs.getDataOutput().writeInt(cnt);
                    result.set(abvs);
                } catch (IOException e) {
                    throw new AlgebricksException(e);
                }
            }

            @Override
            public void init() throws AlgebricksException {
                cnt = 0;
            }
        };
    }

}