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From "Phabricator (JIRA)" <>
Subject [jira] [Commented] (HIVE-3562) Some limit can be pushed down to map stage
Date Mon, 10 Dec 2012 09:43:22 GMT


Phabricator commented on HIVE-3562:

tarball has requested changes to the revision "HIVE-3562 [jira] Some limit can be pushed down
to map stage".

  conf/hive-default.xml.template:1407 Why is optimization disabled by default? This is good
stuff and should be switched on!
  conf/hive-default.xml.template:1413 10 million seems like a really large threshold. Maybe
in the 50k range?
  ql/src/java/org/apache/hadoop/hive/ql/exec/ The current implementation
doesn't look like a heap to me. Why not simply use java.util.PriorityQueue?
  ql/src/java/org/apache/hadoop/hive/ql/exec/ Shouldn't nulls be
equal to each other?
  ql/src/java/org/apache/hadoop/hive/ql/exec/ Better name? TopNHeap?



To: JIRA, tarball, navis
Cc: njain

> Some limit can be pushed down to map stage
> ------------------------------------------
>                 Key: HIVE-3562
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Navis
>            Assignee: Navis
>            Priority: Trivial
>         Attachments: HIVE-3562.D5967.1.patch, HIVE-3562.D5967.2.patch
> Queries with limit clause (with reasonable number), for example
> {noformat}
> select * from src order by key limit 10;
> {noformat}
> makes operator tree, 
> But LIMIT can be partially calculated in RS, reducing size of shuffling.

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