SumFunction-draft.java

/*
 * 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.facebook.presto.operator.window;

import java.util.List;

import com.facebook.presto.operator.PagesIndex;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.type.Type;
import static com.google.common.collect.Iterables.getOnlyElement;

import static com.facebook.presto.spi.type.BigintType.BIGINT;

public class SumFunction
        implements WindowFunction
{
    private final int argumentChannel;
    private int partitionStartPosition;
    private long sum;

    protected SumFunction(List<Integer> argumentChannels)
    {
        this.argumentChannel = getOnlyElement(argumentChannels);
    }

    @Override
    public Type getType()
    {
        return BIGINT;
    }

    @Override
    public void reset(int partitionRowCount, PagesIndex pagesIndex)
    {
        int nextPartitionStartPosition = partitionStartPosition + partitionRowCount;
        long sum = 0;
        for (int i = partitionStartPosition; i < nextPartitionStartPosition; i++) {
            sum += pagesIndex.getLong(argumentChannel, i);
        }
        partitionStartPosition = nextPartitionStartPosition;
    }

    @Override
    public void processRow(BlockBuilder output, boolean newPeerGroup, int peerGroupCount)
    {
        BIGINT.writeLong(output, sum);
    }
}