processing/src/main/java/org/apache/druid/query/aggregation/cardinality/types/LongCardinalityAggregatorColumnSelectorStrategy.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 org.apache.druid.query.aggregation.cardinality.types;

import com.google.common.hash.Hasher;
import org.apache.druid.common.config.NullHandling;
import org.apache.druid.hll.HyperLogLogCollector;
import org.apache.druid.query.aggregation.cardinality.CardinalityAggregator;
import org.apache.druid.segment.BaseLongColumnValueSelector;

/**
 * If performance of this class appears to be a bottleneck for somebody,
 * one simple way to improve it is to split it into two different classes,
 * one that is used when {@link NullHandling#replaceWithDefault()} is false,
 * and one - when it's true, moving this computation out of the tight loop
 */
public class LongCardinalityAggregatorColumnSelectorStrategy
    implements CardinalityAggregatorColumnSelectorStrategy<BaseLongColumnValueSelector>
{
  public static void addLongToCollector(final HyperLogLogCollector collector, final long n)
  {
    collector.add(CardinalityAggregator.HASH_FUNCTION.hashLong(n).asBytes());
  }

  @Override
  public void hashRow(BaseLongColumnValueSelector selector, Hasher hasher)
  {
    if (NullHandling.replaceWithDefault() || !selector.isNull()) {
      hasher.putLong(selector.getLong());
    }
  }

  @Override
  public void hashValues(BaseLongColumnValueSelector selector, HyperLogLogCollector collector)
  {
    if (NullHandling.replaceWithDefault() || !selector.isNull()) {
      addLongToCollector(collector, selector.getLong());
    }
  }
}