Github user nsyca commented on a diff in the pull request:
https://github.com/apache/spark/pull/17520#discussion_r109519728
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -766,6 +771,31 @@ object PushDownPredicate extends Rule[LogicalPlan]
with PredicateHelper {
project.copy(child = Filter(replaceAlias(condition, aliasMap),
grandChild))
+ // Similar to the above Filter over Project
+ // LeftSemi/LeftAnti over Project
+ case join @ Join(project @ Project(projectList, grandChild), rightOp,
+ LeftSemiOrAnti(joinType), joinCond)
+ if !tooSimplePlan(grandChild) &&
+ projectList.forall(_.deterministic) &&
+ !ScalarSubquery.hasScalarSubquery(projectList) &&
+ canPushThroughCondition(grandChild, joinCond, rightOp) =>
+ if (joinCond.isEmpty) {
+ // No join condition, just push down the Join below Project
+ Project(projectList, Join(grandChild, rightOp, joinType, joinCond))
+ } else {
+ // Create a map of Aliases to their values from the child
projection.
+ // e.g., 'SELECT a + b AS c, d ...' produces Map(c -> a + b).
+ val aliasMap = AttributeMap(projectList.collect {
+ case a: Alias => (a.toAttribute, a.child)
+ })
+ val newJoinCond = if (aliasMap.nonEmpty) {
+ Option(replaceAlias(joinCond.get, aliasMap))
+ } else {
+ joinCond
+ }
+ Project(projectList, Join(grandChild, rightOp, joinType,
newJoinCond))
+ }
+
--- End diff --
[To reviewers] Should we separate this into a new rule?
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