[GitHub] [spark] viirya commented on a change in pull request #30093: [SPARK-33183][SQL] Fix Optimizer rule EliminateSorts and add a physical rule to remove redundant sorts

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viirya commented on a change in pull request #30093:
URL: https://github.com/apache/spark/pull/30093#discussion_r513102275



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File path: sql/core/src/main/scala/org/apache/spark/sql/execution/RemoveRedundantSorts.scala
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@@ -0,0 +1,46 @@
+/*
+ * 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.SortOrder
+import org.apache.spark.sql.catalyst.rules.Rule
+import org.apache.spark.sql.internal.SQLConf
+
+/**
+ * Remove redundant SortExec node from the spark plan. A sort node is redundant when
+ * its child satisfies both its sort orders and its required child distribution. Note
+ * this rule differs from the Optimizer rule EliminateSorts in that this rule also checks
+ * if the child satisfies the required distribution so that it is safe to remove not only a
+ * local sort but also a global sort when its child already satisfies required sort orders.
+ */
+case class RemoveRedundantSorts(conf: SQLConf) extends Rule[SparkPlan] {

Review comment:
       Yes, however, this is inevitable for such bug fix and correctness bug fix precedes performance. Since the physical rule is well separated and has a config, it looks okay.




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