kishoreg commented on a change in pull request #4527: Group by with order by URL: https://github.com/apache/incubator-pinot/pull/4527#discussion_r313753832
########## File path: pinot-core/src/main/java/org/apache/pinot/core/operator/OrderByUtils.java ########## @@ -0,0 +1,240 @@ +/** + * 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.pinot.core.operator; + +import java.util.ArrayList; +import java.util.Comparator; +import java.util.HashMap; +import java.util.List; +import java.util.Map; +import org.apache.commons.collections.comparators.ComparableComparator; +import org.apache.pinot.common.request.AggregationInfo; +import org.apache.pinot.common.request.GroupBy; +import org.apache.pinot.common.request.SelectionSort; +import org.apache.pinot.common.utils.BytesUtils; +import org.apache.pinot.common.utils.DataSchema; +import org.apache.pinot.common.utils.primitive.ByteArray; +import org.apache.pinot.core.query.aggregation.AggregationFunctionContext; +import org.apache.pinot.core.query.aggregation.function.AggregationFunction; +import org.apache.pinot.core.query.aggregation.function.AggregationFunctionUtils; + +import static org.apache.pinot.common.utils.DataSchema.*; + + +/** + * Helper methods to perform order by of list of {@link GroupByRecord} + */ +public class OrderByUtils { + + /** + * Constructs the comparator to order the intermediate results + */ + public static Comparator<GroupByRecord> getIntermediateComparator(List<AggregationInfo> aggregationInfos, GroupBy groupBy, + List<SelectionSort> orderBy, DataSchema dataSchema) { + List<OrderByInfo> orderByInfos = constructOrderByInfo(aggregationInfos, groupBy, orderBy, dataSchema); + return getComparator(orderByInfos, true); + } + + /** + * Constructs the comparator to order the final results + */ + public static Comparator<GroupByRecord> getFinalComparator(List<AggregationInfo> aggregationInfos, GroupBy groupBy, + List<SelectionSort> orderBy, DataSchema dataSchema) { + List<OrderByInfo> orderByInfos = constructOrderByInfo(aggregationInfos, groupBy, orderBy, dataSchema); + return getComparator(orderByInfos, false); + } + + /** + * Constructs a comparator given all the {@link OrderByInfo} for the order by clause + */ + private static Comparator<GroupByRecord> getComparator(List<OrderByInfo> orderByInfos, boolean isIntermediate) { + Comparator<GroupByRecord> globalComparator = null; + for (OrderByInfo orderByInfo : orderByInfos) { + OrderType orderType = orderByInfo.getOrderType(); + + Comparator<GroupByRecord> comparator; + if (orderType.equals(OrderType.AGGREGATION_VALUE)) { + comparator = getAggregationComparator(orderByInfo, isIntermediate); + } else { + comparator = getGroupByKeyComparator(orderByInfo); + } + if (globalComparator == null) { + globalComparator = comparator; + } else { + globalComparator = globalComparator.thenComparing(comparator); + } + } + return globalComparator; + } + + /** + * Constructs the comparator for ordering by an aggregation result + * + * When ordering intermediate results, check if the intermediate results are comparable. + * If they are not, extract final result for doing the comparison + */ + private static Comparator<GroupByRecord> getAggregationComparator(OrderByInfo orderByInfo, boolean isIntermediate) { + int index = orderByInfo.getIndex(); + AggregationFunction aggregationFunction = orderByInfo.getAggregationFunction(); + boolean ascending = orderByInfo.isAscending(); + + Comparator<GroupByRecord> comparator; + + // intermediate aggregation results may or may not be comparable + // final aggregation results are always comparable + if (isIntermediate && !aggregationFunction.isIntermediateResultComparable()) { + if (ascending) { + comparator = (v1, v2) -> ComparableComparator.getInstance() + .compare(aggregationFunction.extractFinalResult(v1.getAggregationResults()[index]), + aggregationFunction.extractFinalResult(v2.getAggregationResults()[index])); + } else { + comparator = (v1, v2) -> ComparableComparator.getInstance() + .compare(aggregationFunction.extractFinalResult(v2.getAggregationResults()[index]), + aggregationFunction.extractFinalResult(v1.getAggregationResults()[index])); + } + } else { + if (ascending) { + comparator = (v1, v2) -> ComparableComparator.getInstance() + .compare(v1.getAggregationResults()[index], v2.getAggregationResults()[index]); + } else { + comparator = (v1, v2) -> ComparableComparator.getInstance() + .compare(v2.getAggregationResults()[index], v1.getAggregationResults()[index]); + } + } + return comparator; + } + + /** + * Constructs the comparator for ordering by a group by key + */ + private static Comparator<GroupByRecord> getGroupByKeyComparator(OrderByInfo orderByInfo) { + int index = orderByInfo.getIndex(); + ColumnDataType columnDataType = orderByInfo.getColumnDataType(); + boolean ascending = orderByInfo.isAscending(); + + Comparator<GroupByRecord> comparator; + + switch (columnDataType) { + case INT: + if (ascending) { + comparator = Comparator.comparing(GroupByRecord::getGroupByKey, + Comparator.comparingInt(v -> Integer.valueOf(v[index]))); Review comment: converting string to raw datatype will be very expensive rt? 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