Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/11745#discussion_r56463073
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -306,14 +311,28 @@ object SetOperationPushDown extends Rule[LogicalPlan]
with PredicateHelper {
}
/**
- * Attempts to eliminate the reading of unneeded columns from the query
plan using the following
- * transformations:
+ * Attempts to eliminate the reading of unneeded columns from the query
plan
+ * by pushing Project through Filter.
*
- * - Inserting Projections beneath the following operators:
- * - Aggregate
- * - Generate
- * - Project <- Join
- * - LeftSemiJoin
+ * Note: This rule could reverse the effects of
PushPredicateThroughProject.
+ * This rule should be run before ColumnPruning for ensuring that Project
can be
--- End diff --
I'm a little against to depending on rules order too much, sometimes we
have to as other solutions are way too complex, but for this issue, can we try
to find a more general solution?
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