EdisonWang created SPARK-29343:
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Summary: Eliminate sorts without limit in the subquery of
Join/Aggregation
Key: SPARK-29343
URL: https://issues.apache.org/jira/browse/SPARK-29343
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 3.0.0
Reporter: EdisonWang
The {{Sort}} without {{Limit}} operator in {{Join/GroupBy}} subquery is useless.
For example, {{select count(1) from (select a from test1 order by a)}} is equal
to {{select count(1) from (select a from test1)}}.
'select * from (select a from test1 order by a) t1 join (select b from test2)
t2 on t1.a = t2.b' is equal to {{select * from (select a from test1) t1 join
(select b from test2) t2 on t1.a = t2.b}}.
Remove useless {{Sort}} operator can import performance.
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