maryannxue commented on a change in pull request #25703: [SPARK-29002][SQL] Avoid changing SMJ to BHJ if the build side has a high ratio of empty partitions URL: https://github.com/apache/spark/pull/25703#discussion_r321553775
########## File path: sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/DemoteBroadcastHashJoin.scala ########## @@ -0,0 +1,60 @@ +/* + * 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, LogicalPlan, NO_BROADCAST_HASH} +import org.apache.spark.sql.catalyst.rules.Rule +import org.apache.spark.sql.internal.SQLConf + +/** + * This optimization rule detects a join child that has a high ratio of empty partitions and + * adds a no-broadcast-hash-join hint to avoid it being broadcast. + */ +case class DemoteBroadcastHashJoin(conf: SQLConf) extends Rule[LogicalPlan] { + + private def shouldDemote(plan: LogicalPlan): Boolean = plan match { + case LogicalQueryStage(_, stage: QueryStageExec) + if stage.resultOption.isDefined && + stage.resultOption.get.isInstanceOf[MapOutputStatistics] => + val mapOutputStatistics = stage.resultOption.get.asInstanceOf[MapOutputStatistics] + val partitionCnt = mapOutputStatistics.bytesByPartitionId.length + val nonZeroCnt = mapOutputStatistics.bytesByPartitionId.count(_ > 0) + partitionCnt > 0 && nonZeroCnt > 0 && + (nonZeroCnt * 1.0 / partitionCnt) < conf.nonEmptyPartitionRatioForBroadcastJoin + case _ => false + } + + def apply(plan: LogicalPlan): LogicalPlan = plan.transformDown { + case j @ Join(left, right, _, _, hint) => + var newHint = hint Review comment: You might have misunderstood the logic here. Left and right aren't exclusive here, so it's not an "if-else" logic. ---------------------------------------------------------------- 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: [email protected] With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
