mgaido91 commented on a change in pull request #22957: [SPARK-25951][SQL] Ignore aliases for distributions and orderings URL: https://github.com/apache/spark/pull/22957#discussion_r255409089
########## File path: sql/core/src/main/scala/org/apache/spark/sql/execution/AliasAwareOutputPartitioning.scala ########## @@ -0,0 +1,103 @@ +/* + * 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.analysis.CleanupAliases +import org.apache.spark.sql.catalyst.expressions.{Alias, Expression, NamedExpression} +import org.apache.spark.sql.catalyst.plans.physical.{Partitioning, PartitioningCollection, UnknownPartitioning} + +/** + * Trait for plans which can produce an output partitioned by aliased attributes of their child. + * It rewrites the partitioning attributes of the child with the corresponding new ones which are + * exposed in the output of this plan. It can avoid the presence of redundant shuffles in queries + * caused by the rename of an attribute among the partitioning ones, eg. + * + * spark.range(10).selectExpr("id AS key", "0").repartition($"key").write.saveAsTable("df1") + * spark.range(10).selectExpr("id AS key", "0").repartition($"key").write.saveAsTable("df2") + * sql(""" + * SELECT * FROM + * (SELECT key AS k from df1) t1 + * INNER JOIN + * (SELECT key AS k from df2) t2 + * ON t1.k = t2.k + * """).explain + * + * == Physical Plan == + * *SortMergeJoin [k#56L], [k#57L], Inner + * :- *Sort [k#56L ASC NULLS FIRST], false, 0 + * : +- Exchange hashpartitioning(k#56L, 200) // <--- Unnecessary shuffle operation + * : +- *Project [key#39L AS k#56L] + * : +- Exchange hashpartitioning(key#39L, 200) + * : +- *Project [id#36L AS key#39L] + * : +- *Range (0, 10, step=1, splits=Some(4)) + * +- *Sort [k#57L ASC NULLS FIRST], false, 0 + * +- ReusedExchange [k#57L], Exchange hashpartitioning(k#56L, 200) + */ +trait AliasAwareOutputPartitioning extends UnaryExecNode { + + /** + * `Seq` of `Expression`s which define the ouput of the node. + */ + protected def outputExpressions: Seq[NamedExpression] + + /** + * Returns the valid `Partitioning`s for the node w.r.t its output and its expressions. + */ + final override def outputPartitioning: Partitioning = { + child.outputPartitioning match { + case partitioning: Expression => + val exprToEquiv = partitioning.references.map { attr => Review comment: sure, let me add some comments. Thanks. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on 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]
