[GitHub] [spark] cloud-fan commented on a change in pull request #24331: [SPARK-19712][SQL] Pushdown LeftSemi/LeftAnti below join

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cloud-fan commented on a change in pull request #24331: [SPARK-19712][SQL] Pushdown LeftSemi/LeftAnti below join
URL: https://github.com/apache/spark/pull/24331#discussion_r274389324
 
 

 ##########
 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/PushDownLeftSemiAntiJoin.scala
 ##########
 @@ -159,3 +159,106 @@ object PushDownLeftSemiAntiJoin extends Rule[LogicalPlan] with PredicateHelper {
     }
   }
 }
+
+/**
+ * This rule is a variant of [[PushPredicateThroughJoin]] which can handle
+ * pushing down Left semi and Left Anti joins below a join operator. The
+ * allowable join types are:
+ *  1) Inner
+ *  2) Cross
+ *  3) LeftOuter
+ *  4) RightOuter
+ */
+object PushLeftSemiLeftAntiThroughJoin extends Rule[LogicalPlan] with PredicateHelper {
+  /**
+   * Define an enumeration to identify whether a LeftSemi/LeftAnti join can be pushed down to
+   * the left leg or the right leg of the join.
+   */
+  object pushdownDirection extends Enumeration {
 
 Review comment:
   shall we upper case the first letter?

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