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.topn; import com.google.common.collect.Lists; import com.google.common.collect.Maps; import org.apache.druid.query.Result; import org.apache.druid.query.aggregation.AggregatorFactory; import org.apache.druid.query.dimension.DimensionSpec; import org.joda.time.DateTime; import java.util.Arrays; import java.util.Comparator; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Objects; import java.util.PriorityQueue; /** */ public class TopNLexicographicResultBuilder implements TopNResultBuilder { private static final int LOOP_UNROLL_COUNT = 8; private final DateTime timestamp; private final DimensionSpec dimSpec; private final String previousStop; private final Comparator comparator; private final String[] aggFactoryNames; private final PriorityQueue<DimValHolder> pQueue; private final int threshold; public TopNLexicographicResultBuilder(DateTime timestamp, DimensionSpec dimSpec, int threshold, String previousStop, final Comparator comparator, List<AggregatorFactory> aggFactories) { this.timestamp = timestamp; this.dimSpec = dimSpec; this.previousStop = previousStop; this.comparator = comparator; this.aggFactoryNames = TopNQueryQueryToolChest.extractFactoryName(aggFactories); this.threshold = threshold; this.pQueue = new PriorityQueue<>(threshold + 1, (o1, o2) -> comparator.compare(o2.getDimValue(), o1.getDimValue())); } @Override public TopNResultBuilder addEntry(Comparable dimValueObj, Object dimValIndex, Object[] metricVals) { final String dimValue = Objects.toString(dimValueObj, null); final Map<String, Object> metricValues = Maps.newHashMapWithExpectedSize(metricVals.length + 1); if (shouldAdd(dimValue)) { metricValues.put(dimSpec.getOutputName(), dimValueObj); final int extra = metricVals.length % LOOP_UNROLL_COUNT; switch (extra) { case 7: metricValues.put(aggFactoryNames[6], metricVals[6]); // fall through case 6: metricValues.put(aggFactoryNames[5], metricVals[5]); // fall through case 5: metricValues.put(aggFactoryNames[4], metricVals[4]); // fall through case 4: metricValues.put(aggFactoryNames[3], metricVals[3]); // fall through case 3: metricValues.put(aggFactoryNames[2], metricVals[2]); // fall through case 2: metricValues.put(aggFactoryNames[1], metricVals[1]); // fall through case 1: metricValues.put(aggFactoryNames[0], metricVals[0]); } for (int i = extra; i < metricVals.length; i += LOOP_UNROLL_COUNT) { metricValues.put(aggFactoryNames[i + 0], metricVals[i + 0]); metricValues.put(aggFactoryNames[i + 1], metricVals[i + 1]); metricValues.put(aggFactoryNames[i + 2], metricVals[i + 2]); metricValues.put(aggFactoryNames[i + 3], metricVals[i + 3]); metricValues.put(aggFactoryNames[i + 4], metricVals[i + 4]); metricValues.put(aggFactoryNames[i + 5], metricVals[i + 5]); metricValues.put(aggFactoryNames[i + 6], metricVals[i + 6]); metricValues.put(aggFactoryNames[i + 7], metricVals[i + 7]); } pQueue.add(new DimValHolder.Builder().withDimValue(dimValue).withMetricValues(metricValues).build()); if (pQueue.size() > threshold) { pQueue.poll(); } } return this; } @Override public TopNResultBuilder addEntry(DimensionAndMetricValueExtractor dimensionAndMetricValueExtractor) { Object dimensionValueObj = dimensionAndMetricValueExtractor.getDimensionValue(dimSpec.getOutputName()); String dimensionValue = Objects.toString(dimensionValueObj, null); if (shouldAdd(dimensionValue)) { pQueue.add(new DimValHolder.Builder().withDimValue(dimensionValue) .withMetricValues(dimensionAndMetricValueExtractor.getBaseObject()).build()); if (pQueue.size() > threshold) { pQueue.poll(); } } return this; } @Override public Iterator<DimValHolder> getTopNIterator() { return pQueue.iterator(); } @Override public Result<TopNResultValue> build() { // Pull out top aggregated values final DimValHolder[] holderValueArray = pQueue.toArray(new DimValHolder[0]); Arrays.sort(holderValueArray, (o1, o2) -> comparator.compare(o1.getDimValue(), o2.getDimValue())); return new Result<>(timestamp, new TopNResultValue( Lists.transform(Arrays.asList(holderValueArray), DimValHolder::getMetricValues))); } private boolean shouldAdd(String dimName) { final boolean belowThreshold = pQueue.size() < threshold; final boolean belowMax = belowThreshold || comparator.compare(pQueue.peek().getTopNMetricVal(), dimName) < 0; // Only add if dimName is after previousStop return belowMax && (previousStop == null || comparator.compare(dimName, previousStop) > 0); } }