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A module that is everything required to understands Druid Segments
/*
* Licensed to Metamarkets Group Inc. (Metamarkets) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. Metamarkets licenses this file
* to you 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.druid.query.aggregation.cardinality;
import io.druid.query.aggregation.BufferAggregator;
import io.druid.query.aggregation.hyperloglog.HyperLogLogCollector;
import io.druid.segment.DimensionSelector;
import java.nio.ByteBuffer;
import java.util.List;
public class CardinalityBufferAggregator implements BufferAggregator
{
private final List selectorList;
private final boolean byRow;
private static final byte[] EMPTY_BYTES = HyperLogLogCollector.makeEmptyVersionedByteArray();
public CardinalityBufferAggregator(
List selectorList,
boolean byRow
)
{
this.selectorList = selectorList;
this.byRow = byRow;
}
@Override
public void init(ByteBuffer buf, int position)
{
final ByteBuffer mutationBuffer = buf.duplicate();
mutationBuffer.position(position);
mutationBuffer.put(EMPTY_BYTES);
}
@Override
public void aggregate(ByteBuffer buf, int position)
{
final HyperLogLogCollector collector = HyperLogLogCollector.makeCollector(
(ByteBuffer) buf.duplicate().position(position).limit(
position
+ HyperLogLogCollector.getLatestNumBytesForDenseStorage()
)
);
if (byRow) {
CardinalityAggregator.hashRow(selectorList, collector);
} else {
CardinalityAggregator.hashValues(selectorList, collector);
}
}
@Override
public Object get(ByteBuffer buf, int position)
{
ByteBuffer dataCopyBuffer = ByteBuffer.allocate(HyperLogLogCollector.getLatestNumBytesForDenseStorage());
ByteBuffer mutationBuffer = buf.duplicate();
mutationBuffer.position(position);
mutationBuffer.get(dataCopyBuffer.array());
return HyperLogLogCollector.makeCollector(dataCopyBuffer);
}
@Override
public float getFloat(ByteBuffer buf, int position)
{
throw new UnsupportedOperationException("CardinalityBufferAggregator does not support getFloat()");
}
@Override
public long getLong(ByteBuffer buf, int position)
{
throw new UnsupportedOperationException("CardinalityBufferAggregator does not support getLong()");
}
@Override
public void close()
{
// no resources to cleanup
}
}
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