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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-13807) Extend metadata provider to pull up predicates through Union
Date Fri, 27 May 2016 17:28:13 GMT

    [ https://issues.apache.org/jira/browse/HIVE-13807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15304405#comment-15304405
] 

Ashutosh Chauhan commented on HIVE-13807:
-----------------------------------------

+1

> 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
>         Attachments: HIVE-13807.patch
>
>
> Follow-up of HIVE-13068.
> Currently, when we pull up predicates through Union operation with Calcite metadata provider,
we just create a single disjunction 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 (a list of predicates), 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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