cloud-fan commented on code in PR #53664: URL: https://github.com/apache/spark/pull/53664#discussion_r2721338280
########## sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteCorrelatedInlineTable.scala: ########## @@ -0,0 +1,105 @@ +/* + * 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 org.apache.spark.sql.catalyst.analysis.ResolvedInlineTable +import org.apache.spark.sql.catalyst.expressions.{Alias, SubExprUtils, SubqueryExpression} +import org.apache.spark.sql.catalyst.plans.logical.{CTERelationDef, LogicalPlan, OneRowRelation, Project, Union} +import org.apache.spark.sql.catalyst.rules.Rule + +/** + * Rewrites correlated [[ResolvedInlineTable]] into [[Project]] + [[OneRowRelation]] + [[Union]] + * to enable decorrelation by the existing subquery decorrelation framework. + * + * A correlated inline table contains [[OuterReference]] expressions that refer to columns from + * an outer query. These cannot be evaluated at planning time and must be decorrelated. + * + * The transformation converts each row into a [[Project]] over [[OneRowRelation]], then unions + * them together. This structure allows [[PullupCorrelatedPredicates]] to handle the correlation. + * + * This rule applies to all correlated subquery contexts: scalar subqueries, EXISTS, IN, + * LATERAL subqueries, and CTEs. + * + * Example: + * {{{ + * Input: + * ResolvedInlineTable( + * rows = [[OuterReference(t.c1)], [OuterReference(t.c2)]], + * output = [col1] + * ) + * + * Output: + * Union( + * Project([OuterReference(t.c1) AS col1], OneRowRelation), + * Project([OuterReference(t.c2) AS col1], OneRowRelation) + * ) + * }}} + * + * This rule runs before [[PullupCorrelatedPredicates]] in the optimizer. + */ +object RewriteCorrelatedInlineTable extends Rule[LogicalPlan] { + + def apply(plan: LogicalPlan): LogicalPlan = { + // Transform both plan nodes and expressions containing plans (e.g., SubqueryExpression) + plan.transformUpWithPruning( + _.containsPattern(org.apache.spark.sql.catalyst.trees.TreePattern.INLINE_TABLE_EVAL)) { + case table: ResolvedInlineTable + if table.rows.flatten.exists(SubExprUtils.containsOuter) => + rewriteTable(table) + case cte: CTERelationDef => Review Comment: why match `CTERelationDef` specifically? plan transformation will hit its child automatically. -- 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]
