cloud-fan commented on a change in pull request #29031: URL: https://github.com/apache/spark/pull/29031#discussion_r452665849
########## File path: sql/core/src/main/scala/org/apache/spark/sql/execution/RemoveRedundantProjects.scala ########## @@ -0,0 +1,87 @@ +/* + * 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.aggregate.{Final, PartialMerge} +import org.apache.spark.sql.catalyst.rules.Rule +import org.apache.spark.sql.execution.aggregate.BaseAggregateExec +import org.apache.spark.sql.execution.datasources.v2.DataSourceV2ScanExecBase +import org.apache.spark.sql.execution.window.WindowExec +import org.apache.spark.sql.internal.SQLConf + +/** + * Remove redundant ProjectExec node from the spark plan. A ProjectExec node is redundant when + * - It has the same output attributes and orders as its child's output and the ordering of + * the attributes is required. + * - It has the same output attributes as its child's output when attribute output ordering + * is not required. + * This rule needs to be a physical rule because project nodes are useful during logical + * optimization to prune data. During physical planning, redundant project nodes can be removed + * to simplify the query plan. + */ +case class RemoveRedundantProjects(conf: SQLConf) extends Rule[SparkPlan] { + def apply(plan: SparkPlan): SparkPlan = { + if (!conf.getConf(SQLConf.REMOVE_REDUNDANT_PROJECTS_ENABLED)) { + plan + } else { + removeProject(plan, true) + } + } + + private def removeProject(plan: SparkPlan, requireOrdering: Boolean): SparkPlan = { + plan match { + case p @ ProjectExec(_, child) => + if (isRedundant(p, child, requireOrdering)) { + val newPlan = removeProject(child, requireOrdering) + newPlan.setLogicalLink(child.logicalLink.get) + newPlan + } else { + p.mapChildren(removeProject(_, false)) + } + case op: TakeOrderedAndProjectExec => + op.mapChildren(removeProject(_, false)) + case a: BaseAggregateExec => + // BaseAggregateExec require specific column ordering when mode is Final or PartialMerge. + // See comments in BaseAggregateExec inputAttributes method. + val keepOrdering = a.aggregateExpressions + .exists(ae => ae.mode.equals(Final) || ae.mode.equals(PartialMerge)) + a.mapChildren(removeProject(_, keepOrdering)) + case g: GenerateExec => g.mapChildren(removeProject(_, false)) + // JoinExec ordering requirement will inherit from its parent. If there is no ProjectExec in + // its ancestors, JoinExec should require output columns to be ordered. + case o => o.mapChildren(removeProject(_, requireOrdering)) + } + } + + private def isRedundant( + project: ProjectExec, + child: SparkPlan, + requireOrdering: Boolean): Boolean = { + child match { + // If a DataSourceV2ScanExec node does not support columnar, a ProjectExec node is required + // to convert the rows to UnsafeRow. See DataSourceV2Strategy for more details. + case d: DataSourceV2ScanExecBase if !d.supportsColumnar => false + case _ => + if (requireOrdering) { + project.output.map(_.exprId.id) == child.output.map(_.exprId.id) Review comment: I don't think so. `AttributeReferece.sameRef` doesn't consider qualifier as well. ---------------------------------------------------------------- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
