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Posted to issues@hive.apache.org by "Jesus Camacho Rodriguez (Jira)" <ji...@apache.org> on 2019/11/05 16:15:00 UTC

[jira] [Updated] (HIVE-22454) Remove subplan under "Limit 0"

     [ https://issues.apache.org/jira/browse/HIVE-22454?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jesus Camacho Rodriguez updated HIVE-22454:
-------------------------------------------
    Component/s: CBO

> Remove subplan under "Limit 0"
> ------------------------------
>
>                 Key: HIVE-22454
>                 URL: https://issues.apache.org/jira/browse/HIVE-22454
>             Project: Hive
>          Issue Type: Improvement
>          Components: CBO
>            Reporter: Steve Carlin
>            Priority: Major
>
> After the Calcite upgrade and some fixes, there are plans that have a "limit 0" but then do stuff after 0 rows are selected.
> An example is in filter_union.q.out:
> ...
>       Reduce Operator Tree:
>         Group By Operator
>           aggregations: count(VALUE._col0)
>           keys: KEY._col0 (type: string)
>           mode: mergepartial
>           outputColumnNames: _col0, _col1
>           Statistics: Num rows: 250 Data size: 23750 Basic stats: COMPLETE Column stats: COMPLETE
>           Limit
>             Number of rows: 0
> ...
> We can simplify the plan by maybe creating a dummy table after the Limit 0.



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