Xiaoju Wu created SPARK-27290:
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Summary: remove unneed sort under Aggregate
Key: SPARK-27290
URL: https://issues.apache.org/jira/browse/SPARK-27290
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 2.4.0
Reporter: Xiaoju Wu
I saw some tickets to remove unneeded sort in plan while I think there's
another case in which sort is redundant:
Sort just under an non-orderPreserving node is redundant, for example:
select count(*) from (select a1 from A order by a2);
+- Aggregate
+- Sort
+- FileScan parquet
But one of the existing test cases is conflict with this example:
test("sort should not be removed when there is a node which doesn't guarantee
any order")
{ val orderedPlan = testRelation.select('a, 'b).orderBy('a.asc) val
groupedAndResorted = orderedPlan.groupBy('a)(sum('a)).orderBy('a.asc) val
optimized = Optimize.execute(groupedAndResorted.analyze) val correctAnswer =
groupedAndResorted.analyze comparePlans(optimized, correctAnswer) }
Why is it designed like this? In my opinion, since Aggregate won't pass up the
ordering, the below Sort is useless.
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