Github user nsyca commented on a diff in the pull request:
https://github.com/apache/spark/pull/17520#discussion_r109521667
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -848,11 +967,84 @@ object PushDownPredicate extends Rule[LogicalPlan]
with PredicateHelper {
filter
}
+ // Similar to the above Filter over Union
+ // LeftSemi/LeftAnti over Union
+ case join @ Join(union: Union, rightOp, LeftSemiOrAnti(joinType),
joinCond) =>
+ if (joinCond.isEmpty) {
+ // Push down the Join below Union
+ val newGrandChildren = union.children.map { grandchild =>
+ Join(grandchild, rightOp, joinType, joinCond)
+ }
+ union.withNewChildren(newGrandChildren)
+ } else {
+ // Union could change the rows, so non-deterministic predicate
can't be pushed down
+ val (candidates, containingNonDeterministic) =
+ splitConjunctivePredicates(joinCond.get).span(_.deterministic)
+
+ val (pushDown, rest) = candidates.partition { cond =>
+ !SubqueryExpression.hasCorrelatedSubquery(cond) &&
+ !SubExprUtils.containsOuter(cond)
+ }
+ val stayUp = rest ++ containingNonDeterministic
+
+ if (pushDown.nonEmpty) {
+ val pushDownCond = pushDown.reduceLeft(And)
+ val output = union.output
+ val newGrandChildren = union.children.map { grandchild =>
+ val newCond = pushDownCond transform {
+ case e if output.exists(_.semanticEquals(e)) =>
+ grandchild.output(output.indexWhere(_.semanticEquals(e)))
+ }
+ assert(newCond.references.subsetOf(grandchild.outputSet ++
rightOp.outputSet))
+ Join(grandchild, rightOp, joinType, Option(newCond))
+ }
+ val newUnion = union.withNewChildren(newGrandChildren)
+ if (stayUp.isEmpty) newUnion else Filter(stayUp.reduceLeft(And),
newUnion)
+ } else {
+ // Nothing to push down
+ join
+ }
+ }
+
--- End diff --
Similar to the LeftSemi/LeftAnti over Aggregate, pushing down
LeftSemi/LeftAnti under a Union means we need to repeat the processing of
LeftSemi/LeftAnti once for each branch of the Union.
This code is added to preserve the existing behaviour.
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