leanken commented on a change in pull request #29104:
URL: https://github.com/apache/spark/pull/29104#discussion_r458152176



##########
File path: 
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala
##########
@@ -388,3 +390,36 @@ object PhysicalWindow {
     case _ => None
   }
 }
+
+object ExtractSingleColumnNullAwareAntiJoin extends JoinSelectionHelper with 
PredicateHelper {
+
+  // SingleColumn NullAwareAntiJoin
+  // streamedSideKeys, buildSideKeys
+  // currently these two return Seq[Expression] should have only one element
+  private type ReturnType = (Seq[Expression], Seq[Expression])
+
+  /**
+   * See. [SPARK-32290]
+   * LeftAnti(condition: Or(EqualTo(a=b), IsNull(EqualTo(a=b)))
+   * will almost certainly be planned as a Broadcast Nested Loop join,
+   * which is very time consuming because it's an O(M*N) calculation.
+   * But if it's a single column case, and buildSide data is small enough,
+   * O(M*N) calculation could be optimized into O(M) using hash lookup instead 
of loop lookup.
+   */
+  def unapply(join: Join): Option[ReturnType] = join match {
+    case Join(left, right, LeftAnti,
+      Some(Or(equalTo @ EqualTo(leftAttr: AttributeReference, rightAttr: 
AttributeReference),
+        IsNull(EqualTo(tmpLeft: AttributeReference, tmpRight: 
AttributeReference)))), _)
+        if SQLConf.get.nullAwareAntiJoinOptimizeEnabled &&
+          leftAttr.semanticEquals(tmpLeft) && 
rightAttr.semanticEquals(tmpRight) &&
+          canBroadcastBySize(right, SQLConf.get) &&

Review comment:
       I see your point, event if the canBroadcastBySize = false, pick up the 
optimization will still be the best option, will do the update. thanks




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