[GitHub] [spark] cloud-fan commented on a change in pull request #35214: [SPARK-37915][SQL] Push down deterministic projection through SQL UNION and combine them

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

cloud-fan commented on a change in pull request #35214:
URL: https://github.com/apache/spark/pull/35214#discussion_r785702146



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -766,18 +767,24 @@ object PushProjectionThroughUnion extends Rule[LogicalPlan] with PredicateHelper
     _.containsAllPatterns(UNION, PROJECT)) {
 
     // Push down deterministic projection through UNION ALL
-    case p @ Project(projectList, u: Union) =>
+    case Project(projectList, u: Union) if projectList.forall(_.deterministic) =>
       assert(u.children.nonEmpty)
-      if (projectList.forall(_.deterministic)) {
-        val newFirstChild = Project(projectList, u.children.head)
-        val newOtherChildren = u.children.tail.map { child =>
-          val rewrites = buildRewrites(u.children.head, child)
-          Project(projectList.map(pushToRight(_, rewrites)), child)
-        }
-        u.copy(children = newFirstChild +: newOtherChildren)
-      } else {
-        p
+      val newFirstChild = Project(projectList, u.children.head)
+      val newOtherChildren = u.children.tail.map { child =>
+        val rewrites = buildRewrites(u.children.head, child)
+        Project(projectList.map(pushToRight(_, rewrites)), child)
+      }
+      u.copy(children = newFirstChild +: newOtherChildren)
+
+    // Push down deterministic projection through SQL UNION
+    case Project(projectList, Distinct(u: Union)) if projectList.forall(_.deterministic) =>

Review comment:
       hmm, how does this help eliminate aggregates?




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