Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/10073#discussion_r46353733
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -712,6 +711,49 @@ object PushPredicateThroughAggregate extends
Rule[LogicalPlan] with PredicateHel
}
/**
+ * Reorder the joins so that the bottom ones have at least one condition.
+ */
+object ReorderJoin extends Rule[LogicalPlan] with PredicateHelper {
+
+ /**
+ * Reorder the joins so that the bottom ones have at least one
condition.
+ */
+ def reorder(
+ input: LogicalPlan,
+ joins: Seq[LogicalPlan],
+ conditions: Seq[Expression]): LogicalPlan = {
+ // filter out the conditions that could be pushed down to `joined`
+ val otherConditions = conditions.filterNot { cond =>
+ cond.references.subsetOf(input.outputSet)
+ }
+ if (joins.isEmpty) {
--- End diff --
I would have the pattern return `None` if there are no joins so you don't
have to handle this case.
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