Github user windpiger commented on a diff in the pull request:
https://github.com/apache/spark/pull/16255#discussion_r92311295
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -416,8 +418,8 @@ object ColumnPruning extends Rule[LogicalPlan] {
case w: Window if w.windowExpressions.isEmpty => w.child
// Eliminate no-op Projects
- case p @ Project(_, child) if sameOutput(child.output, p.output) =>
child
-
+ case p @ Project(_, child) if sameOutput(child.output, p.output) =>
+ if (child.isInstanceOf[CatalogRelation]) p else child
--- End diff --
yes, it will transform the right side of the join, and the problem happened
when replace the right side of the join. Above step 5, it apply
RemoveAliasOnlyProject rule on step 4's plan, which replace col#6 with col#9,
but it does not have effect on `Project [col#9 AS col#6]` of the right side of
the join. I think the right side `Project [col#9 AS col#6]` should be changed
to `Project [col#9]`
```
Project [col#9 AS c1#4, col#10 AS c2#5]
+- Join Cross
:- Join Cross
: :- Project
: : +- MetastoreRelation default, p1
: +- MetastoreRelation default, p2
+- !Project [col#9 AS col#10]
+- Join Cross
:- Project
: +- MetastoreRelation default, p1
+- Project [col#9 AS col#6]
+- MetastoreRelation default, p2
```
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