Test build #41418 has finished for PR 8379 at commit 009aadb.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

hmm. seems it triggers another bug?

btw, the failed test is org.apache.spark.sql.SQLQuerySuite.grouping on nested fields.

Before 1.5, ExtractValue chain may have intermedia and unnecessary Aliases inside it, so we trim Aliases upon ExtractValue before compare 2 Expressions in a lot places including here.
However, when we use transformDown, we may loose the top level Alias. For example, 'a.getField("b") is a grouping expression and 'a.getField("b").as("attribute") is an aggregate expression,
with transformDown, the rewritten aggregate expression will be 'a.getField("b") which is wrong.

The commit to fix the wrong Alias trimming is da7bbb9, which is not easy to backport I think. So maybe we need to add some ugly code to hadle the top level Aliases specially.

btw I have sent a PR on your branch, let's see if that can work :)

Test build #41426 has finished for PR 8379 at commit afcfad9.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

LGTM

Thanks guys, merged!