GitHub user gatorsmile opened a pull request:
https://github.com/apache/spark/pull/10963
[SPARK-12989] [SQL] Delaying Alias Cleanup after ExtractWindowExpressions
In the rule `ExtractWindowExpressions`, we simply replace alias by the
name. However, this will cause an issue exposed by the following case:
```scala
val data = Seq(("a", "b", "c", 3), ("c", "b", "a", 3)).toDF("A", "B", "C",
"num")
.withColumn("Data", struct("A", "B", "C"))
.drop("A")
.drop("B")
.drop("C")
val winSpec = Window.partitionBy("Data.A", "Data.B").orderBy($"num".desc)
data.select($"*", max("num").over(winSpec) as "max").explain(true)
```
In this case, both `Data.A` and `Data.B` are `alias` in
`WindowSpecDefinition`. If we replace these alias expression by their alias
names, we are unable to know what they are since they will not be put in
`missingExpr` too.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gatorsmile/spark seletStarAfterColDrop
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/10963.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #10963
----
commit 468abca15ae55a95b53fa427fbac7846e1da9f76
Author: gatorsmile <[email protected]>
Date: 2016-01-28T02:58:28Z
delaying alias cleanup
----
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