[jira] [Work started] (HIVE-13807) Extend metadata provider to pull up predicates through Union

["Jesus Camacho Rodriguez (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-13807?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on HIVE-13807 started by Jesus Camacho Rodriguez.
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> Extend metadata provider to pull up predicates through Union
> ------------------------------------------------------------
>
>                 Key: HIVE-13807
>                 URL: https://issues.apache.org/jira/browse/HIVE-13807
>             Project: Hive
>          Issue Type: Sub-task
>          Components: CBO
>    Affects Versions: 2.1.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>
> Follow-up of HIVE-13068.
> Currently, when we pull up predicates through Union operation with Calcite metadata provider, we just create a single conjunction of pulled up predicates. 
> E.g. Assume operators _I1, I2, I3_ with predicates {{P1, P2, P3}} that can be pulled up through them, respectively.
> For an operation _Union (I1, I2, I3)_ we infer a new predicate {{Pu}}, such that {{Pu = P1 OR P2 OR P3}}.
> While this is correct, we miss some chances for simplification e.g. if there are common factors in P1, P2, and P3. Further, this inference differs slightly from the way that the metadata provider pulls up predicates for other operators, thus breaking some assumptions and missing some optimization opportunities.
> Ex. ql/src/test/results/clientpositive/input26.q.out
> {noformat}
> explain
> select * from (
>   select * from (select * from srcpart a where a.ds = '2008-04-08' and a.hr = '11' order by a.key limit 5)pa
>     union all
>   select * from (select * from srcpart b where b.ds = '2008-04-08' and b.hr = '14' limit 5)pb
> )subq
> {noformat}



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