cloud-fan commented on a change in pull request #29104:
URL: https://github.com/apache/spark/pull/29104#discussion_r460646928
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala
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@@ -388,3 +390,37 @@ object PhysicalWindow {
case _ => None
}
}
+
+object ExtractSingleColumnNullAwareAntiJoin extends JoinSelectionHelper with
PredicateHelper {
+
+ // TODO support multi column NULL-aware anti join in future.
+ // See. http://www.vldb.org/pvldb/vol2/vldb09-423.pdf Section 6
+ // multi-column null aware anti join is much more complicated than single
column ones.
+
+ // streamedSideKeys, buildSideKeys
+ 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(leftAttr: AttributeReference, rightAttr:
AttributeReference),
+ IsNull(EqualTo(tmpLeft: AttributeReference, tmpRight:
AttributeReference)))), _)
Review comment:
how about
```
Some(Or(e @ EqualTo(leftAttr: AttributeReference, rightAttr:
AttributeReference),
IsNull(e2: EqualTo) if ... && e.semanticEquals(e2)
```
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