Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/11235#discussion_r55245770
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -144,6 +146,56 @@ object EliminateSerialization extends
Rule[LogicalPlan] {
}
/**
+ * Add Filter to left and right of an inner Join to filter out rows with
null keys.
+ * So we may not need to check nullability of keys while joining. Besides,
by filtering
+ * out keys with null, we can also reduce data size in Join.
+ */
+object AddFilterOfNullForInnerJoin extends Rule[LogicalPlan] with
PredicateHelper {
--- End diff --
We could also do this for semi join and outer join, should we call it
AddFilterOfNullForEquiJoin ?
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