viirya commented on code in PR #43623: URL: https://github.com/apache/spark/pull/43623#discussion_r1379248105
########## sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteWithExpression.scala: ########## @@ -0,0 +1,99 @@ +/* + * 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.catalyst.optimizer + +import scala.collection.mutable + +import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute, AttributeMap, CommonExpressionRef, Expression, With} +import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Project} +import org.apache.spark.sql.catalyst.rules.Rule +import org.apache.spark.sql.catalyst.trees.TreePattern.{COMMON_EXPR_REF, WITH_EXPRESSION} + +/** + * Rewrites the `With` expressions by adding a `Project` to pre-evaluate the common expressions, or + * just inline them if they are cheap. + * + * Note: For now we only use `With` in a few `RuntimeReplaceable` expressions. If we expand its + * usage, we should support aggregate/window functions as well. + */ +object RewriteWithExpression extends Rule[LogicalPlan] { + override def apply(plan: LogicalPlan): LogicalPlan = { + plan.transformWithPruning(_.containsPattern(WITH_EXPRESSION)) { + case p if p.expressions.exists(_.containsPattern(WITH_EXPRESSION)) => + val commonExprs = mutable.ArrayBuffer.empty[Alias] + // `With` can be nested, we should only rewrite the leaf `With` expression, as the outer + // `With` needs to add its own Project, in the next iteration when it becomes leaf. + // This is done via "transform down" and check if the common expression definitions does not + // contain nested `With`. + var newPlan: LogicalPlan = p.transformExpressionsDown { + case With(child, defs) if defs.forall(!_.containsPattern(WITH_EXPRESSION)) => + val idToCheapExpr = mutable.HashMap.empty[Long, Expression] + val idToNonCheapExpr = mutable.HashMap.empty[Long, Alias] + defs.foreach { commonExprDef => + if (CollapseProject.isCheap(commonExprDef.child)) { + idToCheapExpr(commonExprDef.id) = commonExprDef.child + } else { + // TODO: we should calculate the ref count and also inline the common expression + // if it's ref count is 1. + val alias = Alias(commonExprDef.child, s"_common_expr_${commonExprDef.id}")() + commonExprs += alias + idToNonCheapExpr(commonExprDef.id) = alias + } + } + + child.transformWithPruning(_.containsPattern(COMMON_EXPR_REF)) { + case ref: CommonExpressionRef => + idToCheapExpr.getOrElse(ref.id, idToNonCheapExpr(ref.id).toAttribute) + } + } + + var exprsToAdd = commonExprs.toSeq + val newChildren = p.children.map { child => Review Comment: Shouldn't be? ```suggestion val newChildren = newPlan.children.map { child => ``` -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
