viirya commented on a change in pull request #23964: [SPARK-26975][SQL] Support nested-column pruning over limit/sample/repartition URL: https://github.com/apache/spark/pull/23964#discussion_r266520690
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/NestedColumnAliasing.scala ########## @@ -0,0 +1,151 @@ +/* + * 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.expressions._ +import org.apache.spark.sql.catalyst.plans.logical._ +import org.apache.spark.sql.internal.SQLConf +import org.apache.spark.sql.types._ + +/** + * This aims to handle a nested column aliasing pattern inside the `ColumnPruning` optimizer rule. + * If a project or its child references to nested fields, and not all the fields + * in a nested attribute are used, we can substitute them by alias attributes; then a project + * of the nested fields as aliases on the children of the child will be created. + */ +object NestedColumnAliasing { + + def unapply(plan: LogicalPlan) + : Option[(Map[GetStructField, Alias], Map[ExprId, Seq[Alias]])] = plan match { + case Project(projectList, child) + if SQLConf.get.nestedSchemaPruningEnabled && canProjectPushThrough(child) => Review comment: This rule applies even Spark can't prune nested fields. For example, when reading from data sources don't support nested schema pruning. This is a special rule that only makes sense when pruning nested fields. But now it is applied to all queries. @dongjoon-hyun WDYT? Shall we apply it when pruning nested fields happens actually? ---------------------------------------------------------------- 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]
