com.metamx.druid.aggregation.HistogramBufferAggregator.java Source code

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Here is the source code for com.metamx.druid.aggregation.HistogramBufferAggregator.java

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/*
 * Druid - a distributed column store.
 * Copyright (C) 2012  Metamarkets Group Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

package com.metamx.druid.aggregation;

import com.google.common.primitives.Floats;
import com.google.common.primitives.Longs;
import com.metamx.druid.processing.FloatMetricSelector;

import java.nio.ByteBuffer;
import java.util.Arrays;

public class HistogramBufferAggregator implements BufferAggregator {
    private final FloatMetricSelector selector;
    private final float[] breaks;
    private final int minOffset;
    private final int maxOffset;

    public HistogramBufferAggregator(FloatMetricSelector selector, float[] breaks) {
        this.selector = selector;
        this.breaks = breaks;
        this.minOffset = Longs.BYTES * (breaks.length + 1);
        this.maxOffset = this.minOffset + Floats.BYTES;
    }

    @Override
    public void init(ByteBuffer buf, int position) {
        ByteBuffer mutationBuffer = buf.duplicate();
        mutationBuffer.position(position);

        final long[] bins = new long[breaks.length + 1];
        mutationBuffer.asLongBuffer().put(bins);
        mutationBuffer.putFloat(position + minOffset, Float.MAX_VALUE);
        mutationBuffer.putFloat(position + maxOffset, Float.MIN_VALUE);
    }

    @Override
    public void aggregate(ByteBuffer buf, int position) {
        final float value = selector.get();
        final int minPos = position + minOffset;
        final int maxPos = position + maxOffset;

        if (value < buf.getFloat(minPos))
            buf.putFloat(minPos, value);
        if (value > buf.getFloat(maxPos))
            buf.putFloat(maxPos, value);

        int index = Arrays.binarySearch(breaks, value);
        index = (index >= 0) ? index : -(index + 1);

        final int offset = position + (index * Longs.BYTES);
        final long count = buf.getLong(offset);
        buf.putLong(offset, count + 1);
    }

    @Override
    public Object get(ByteBuffer buf, int position) {
        long[] bins = new long[breaks.length + 1];
        ByteBuffer mutationBuffer = buf.duplicate();
        mutationBuffer.position(position);
        mutationBuffer.asLongBuffer().get(bins);

        float min = mutationBuffer.getFloat(position + minOffset);
        float max = mutationBuffer.getFloat(position + maxOffset);
        return new Histogram(breaks, bins, min, max);
    }

    @Override
    public float getFloat(ByteBuffer buf, int position) {
        throw new UnsupportedOperationException("HistogramBufferAggregator does not support getFloat()");
    }

    @Override
    public void close() {
        // no resources to cleanup
    }
}