Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/7957#discussion_r37049236
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -968,3 +961,61 @@ object EliminateSubQueries extends Rule[LogicalPlan] {
case Subquery(_, child) => child
}
}
+
+/**
+ * Cleans up unnecessary Aliases inside the plan. Basically we only need
Alias as a top level
+ * expression in Project(project list) or Aggregate(aggregate expressions)
or
+ * Window(window expressions).
+ */
+object CleanupAliases extends Rule[LogicalPlan] {
--- End diff --
I have opened https://github.com/apache/spark/pull/8159 to improve the
`withColumn`, but left the code here to see if we can pass the tests.
This PR did 2 things:
1. use `Alias` instead of `UnresolvedAlias` when resolve nested column in
`LogicalPlan.resolve`
2. clean unnecessary aliases at the end of analysis
If we only do `1`, some tests will fail as we need to trim aliases in the
middle of getField chain. If we only do `2`, it can't fix any bugs. So I put
them together here.
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