cloud-fan commented on a change in pull request #32550: URL: https://github.com/apache/spark/pull/32550#discussion_r638849475
########## File path: sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/DynamicJoinSelection.scala ########## @@ -0,0 +1,86 @@ +/* + * 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.adaptive + +import org.apache.spark.MapOutputStatistics +import org.apache.spark.sql.catalyst.plans.logical.{HintInfo, Join, JoinStrategyHint, LogicalPlan, NO_BROADCAST_HASH, PREFER_SHUFFLE_HASH, SHUFFLE_HASH} +import org.apache.spark.sql.catalyst.rules.Rule + +/** + * This optimization rule includes two join selection: + * 1. detects a join child that has a high ratio of empty partitions and adds a + * NO_BROADCAST_HASH hint to avoid it being broadcast. + * 2. detects a join child that every partition size less than local map threshold and adds a + * PREFER_SHUFFLE_HASH hint to encourage being shuffle hash join instead of sort merge join. + * 3. if a join satisfies both NO_BROADCAST_HASH and PREFER_SHUFFLE_HASH, + * then add a SHUFFLE_HASH hint. + */ +object DynamicJoinSelection extends Rule[LogicalPlan] { + + private def shouldDemoteBroadcastHashJoin(mapStats: MapOutputStatistics): Boolean = { + val partitionCnt = mapStats.bytesByPartitionId.length + val nonZeroCnt = mapStats.bytesByPartitionId.count(_ > 0) + partitionCnt > 0 && nonZeroCnt > 0 && + (nonZeroCnt * 1.0 / partitionCnt) < conf.nonEmptyPartitionRatioForBroadcastJoin + } + + private def preferShuffledHashJoin(mapStats: MapOutputStatistics): Boolean = { + val localMapThreshold = conf.shuffleHashJoinLocalMapThreshold + mapStats.bytesByPartitionId.forall(_ <= localMapThreshold) + } + + private def selectJoinStrategy(plan: LogicalPlan): Option[JoinStrategyHint] = plan match { + case LogicalQueryStage(_, stage: ShuffleQueryStageExec) if stage.resultOption.get().isDefined + && stage.mapStats.isDefined => + val demoteBroadcastHash = shouldDemoteBroadcastHashJoin(stage.mapStats.get) + val preferShuffleHash = preferShuffledHashJoin(stage.mapStats.get) + if (demoteBroadcastHash && preferShuffleHash) { + Some(SHUFFLE_HASH) + } else if (demoteBroadcastHash) { + Some(NO_BROADCAST_HASH) + } else if (preferShuffleHash) { + Some(PREFER_SHUFFLE_HASH) + } else { + None + } + + case _ => None + } + + def apply(plan: LogicalPlan): LogicalPlan = plan.transformDown { + case j @ Join(left, right, _, _, hint) => + var newHint = hint + if (!hint.leftHint.exists(_.strategy.isDefined)) { + selectJoinStrategy(left).foreach { strategy => + newHint = newHint.copy(leftHint = + Some(hint.leftHint.getOrElse(HintInfo()).copy(strategy = Some(strategy)))) + } + } + if (!hint.rightHint.exists(_.strategy.isDefined)) { + selectJoinStrategy(right).foreach { strategy => + newHint = newHint.copy(rightHint = + Some(hint.rightHint.getOrElse(HintInfo()).copy(strategy = Some(strategy)))) + } + } Review comment: It seems possible that both sides have `PREFER_SHUFFLE_HASH` hint. How do we decide the build side? -- 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. 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
