[GitHub] [spark] Ngone51 commented on a change in pull request #31470: [SPARK-34354][SQL] Fix failure when apply CostBasedJoinReorder on self-join

[GitBox <gi...@apache.org>]

Ngone51 commented on a change in pull request #31470:
URL: https://github.com/apache/spark/pull/31470#discussion_r590479999



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/DeduplicateRelations.scala
##########
@@ -0,0 +1,224 @@
+/*
+ * 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.analysis
+
+import scala.collection.mutable.ArrayBuffer
+
+import org.apache.spark.sql.catalyst.expressions.{Alias, AttributeMap, AttributeSet, NamedExpression}
+import org.apache.spark.sql.catalyst.plans.logical.{Aggregate, Except, Expand, FlatMapCoGroupsInPandas, FlatMapGroupsInPandas, Generate, Intersect, Join, LogicalPlan, MapInPandas, Project, SerializeFromObject, Union, Window}
+import org.apache.spark.sql.catalyst.rules.Rule
+
+object DeduplicateRelations extends Rule[LogicalPlan] {
+
+  override def apply(plan: LogicalPlan): LogicalPlan = {
+    renewDuplicatedRelations(Nil, plan)._1.resolveOperatorsUp {
+      case p: LogicalPlan if !p.childrenResolved => p
+      // To resolve duplicate expression IDs for Join.
+      case j @ Join(left, right, _, _, _) if !j.duplicateResolved =>
+        j.copy(right = dedupRight(left, right))
+      // intersect/except will be rewritten to join at the beginning of optimizer. Here we need to
+      // deduplicate the right side plan, so that we won't produce an invalid self-join later.
+      case i @ Intersect(left, right, _) if !i.duplicateResolved =>
+        i.copy(right = dedupRight(left, right))
+      case e @ Except(left, right, _) if !e.duplicateResolved =>
+        e.copy(right = dedupRight(left, right))
+      // Only after we finish by-name resolution for Union
+      case u: Union if !u.byName && !u.duplicateResolved =>
+        // Use projection-based de-duplication for Union to avoid breaking the checkpoint sharing
+        // feature in streaming.
+        val newChildren = u.children.foldRight(Seq.empty[LogicalPlan]) { (head, tail) =>
+          head +: tail.map {
+            case child if head.outputSet.intersect(child.outputSet).isEmpty =>
+              child
+            case child =>
+              val projectList = child.output.map { attr =>
+                Alias(attr, attr.name)()
+              }
+              Project(projectList, child)
+          }
+        }
+        u.copy(children = newChildren)
+    }
+  }
+
+  private def renewDuplicatedRelations(

Review comment:
       yes




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