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Posted to issues@spark.apache.org by "EdisonWang (Jira)" <ji...@apache.org> on 2019/10/03 09:23:00 UTC

[jira] [Created] (SPARK-29343) Eliminate sorts without limit in the subquery of Join/Aggregation

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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