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A module that is everything required to understands Druid Segments

There is a newer version: 0.12.3

/*
 * 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.topn;

/**
 */
public class TopNAlgorithmSelector
{
  private final int cardinality;
  private final int numBytesPerRecord;

  private volatile boolean hasExtractionFn;
  private volatile boolean aggregateAllMetrics;
  private volatile boolean aggregateTopNMetricFirst;

  public TopNAlgorithmSelector(int cardinality, int numBytesPerRecord)
  {
    this.cardinality = cardinality;
    this.numBytesPerRecord = numBytesPerRecord;
  }

  public void setHasExtractionFn(boolean hasExtractionFn)
  {
    this.hasExtractionFn = hasExtractionFn;
  }

  public void setAggregateAllMetrics(boolean aggregateAllMetrics)
  {
    this.aggregateAllMetrics = aggregateAllMetrics;
  }

  public void setAggregateTopNMetricFirst(boolean aggregateTopNMetricFirst)
  {
    // These are just heuristics based on an analysis of where an inflection point may lie to switch
    // between different algorithms
    if (cardinality > 400000 && numBytesPerRecord > 100) {
      this.aggregateTopNMetricFirst = aggregateTopNMetricFirst;
    }
  }

  public boolean isHasExtractionFn()
  {
    return hasExtractionFn;
  }

  public boolean isAggregateAllMetrics()
  {
    return aggregateAllMetrics;
  }

  public boolean isAggregateTopNMetricFirst()
  {
    return aggregateTopNMetricFirst;
  }
}