tanelk commented on a change in pull request #34702: URL: https://github.com/apache/spark/pull/34702#discussion_r760180464
########## File path: sql/core/src/main/scala/org/apache/spark/sql/execution/ReplaceHashWithSortAgg.scala ########## @@ -0,0 +1,139 @@ +/* + * 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.spark.sql.execution + +import org.apache.spark.sql.catalyst.expressions.SortOrder +import org.apache.spark.sql.catalyst.expressions.aggregate.{Complete, Final, Partial} +import org.apache.spark.sql.catalyst.rules.Rule +import org.apache.spark.sql.execution.aggregate.HashAggregateExec +import org.apache.spark.sql.internal.SQLConf + +/** + * Replace [[HashAggregateExec]] with [[SortAggregateExec]] in the spark plan if: + * + * 1. The plan is a pair of partial and final [[HashAggregateExec]], and the child of partial + * aggregate satisfies the sort order of corresponding [[SortAggregateExec]]. + * or + * 2. The plan is a [[HashAggregateExec]], and the child satisfies the sort order of + * corresponding [[SortAggregateExec]]. + * + * Examples: + * 1. aggregate after join: + * + * HashAggregate(t1.i, SUM, final) + * | SortAggregate(t1.i, SUM, complete) + * HashAggregate(t1.i, SUM, partial) => | + * | SortMergeJoin(t1.i = t2.j) + * SortMergeJoin(t1.i = t2.j) + * + * 2. aggregate after sort: + * + * HashAggregate(t1.i, SUM, partial) SortAggregate(t1.i, SUM, partial) + * | => | + * Sort(t1.i) Sort(t1.i) + * + * [[HashAggregateExec]] can be replaced when its child satisfies the sort order of + * corresponding [[SortAggregateExec]]. [[SortAggregateExec]] is faster in the sense that + * it does not have hashing overhead of [[HashAggregateExec]]. + */ +object ReplaceHashWithSortAgg extends Rule[SparkPlan] { + def apply(plan: SparkPlan): SparkPlan = { + if (!conf.getConf(SQLConf.REPLACE_HASH_WITH_SORT_AGG_ENABLED)) { + plan + } else { + replaceHashAgg(plan) + } + } + + /** + * Replace [[HashAggregateExec]] with [[SortAggregateExec]]. + */ + private def replaceHashAgg(plan: SparkPlan): SparkPlan = { + plan.transformDown { + case hashAgg: HashAggregateExec if hashAgg.groupingExpressions.nonEmpty => + val sortAgg = hashAgg.toSortAggregate + hashAgg.child match { + case partialAgg: HashAggregateExec if isPartialAgg(partialAgg, hashAgg) => + if (SortOrder.orderingSatisfies( + partialAgg.child.outputOrdering, sortAgg.requiredChildOrdering.head)) { + sortAgg.copy( + aggregateExpressions = sortAgg.aggregateExpressions.map(_.copy(mode = Complete)), + child = partialAgg.child) + } else { + hashAgg + } + case other => + if (SortOrder.orderingSatisfies( + other.outputOrdering, sortAgg.requiredChildOrdering.head)) { + sortAgg + } else { + hashAgg + } + } + case other => other + } + } + + /** + * Check if `partialAgg` to be partial aggregate of `finalAgg`. + */ + private def isPartialAgg(partialAgg: HashAggregateExec, finalAgg: HashAggregateExec): Boolean = { Review comment: This looks like reverse enginering the `AggUtils`. Could we just link the partial and final agg when they are constructed? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org
