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Druid Aggregators based on datasketches lib http://datasketches.github.io/

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/*
 * 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.datasketches.quantiles;

import com.yahoo.sketches.quantiles.DoublesSketch;
import com.yahoo.sketches.quantiles.DoublesUnion;

import io.druid.query.aggregation.Aggregator;
import io.druid.segment.ColumnValueSelector;

public class DoublesSketchMergeAggregator implements Aggregator
{

  private final ColumnValueSelector selector;
  private DoublesUnion union;

  public DoublesSketchMergeAggregator(final ColumnValueSelector selector, final int k)
  {
    this.selector = selector;
    union = DoublesUnion.builder().setMaxK(k).build();
  }

  @Override
  public synchronized void aggregate()
  {
    final DoublesSketch sketch = selector.getObject();
    if (sketch == null) {
      return;
    }
    union.update(sketch);
  }

  @Override
  public synchronized Object get()
  {
    return union.getResult();
  }

  @Override
  public float getFloat()
  {
    throw new UnsupportedOperationException("Not implemented");
  }

  @Override
  public long getLong()
  {
    throw new UnsupportedOperationException("Not implemented");
  }

  @Override
  public synchronized void close()
  {
    union = null;
  }

}