Java tutorial
/* * 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> { @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()) { collector.add(CardinalityAggregator.hashFn.hashLong(selector.getLong()).asBytes()); } } }