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Posted to dev@hive.apache.org by "Hudson (JIRA)" <ji...@apache.org> on 2013/01/09 11:28:11 UTC
[jira] [Commented] (HIVE-3550) Early skipping for limit operator at
reduce stage
[ https://issues.apache.org/jira/browse/HIVE-3550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13548064#comment-13548064 ]
Hudson commented on HIVE-3550:
------------------------------
Integrated in Hive-trunk-hadoop2 #54 (See [https://builds.apache.org/job/Hive-trunk-hadoop2/54/])
HIVE-3550 Early skipping for limit operator at reduce stage
(Navis via namit) (Revision 1395796)
Result = ABORTED
namit : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1395796
Files :
* /hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/exec/ExecReducer.java
> Early skipping for limit operator at reduce stage
> -------------------------------------------------
>
> Key: HIVE-3550
> URL: https://issues.apache.org/jira/browse/HIVE-3550
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Navis
> Assignee: Navis
> Priority: Trivial
> Fix For: 0.10.0
>
> Attachments: HIVE-3550.D5943.1.patch
>
>
> Queries with limit clause whose final result is from reduce stage could not be early exited like map stage. But it seemed possible to just skip remaining lines. It can be accomplished by adding just two lines. Is there any reason we should not to do that?
> {noformat}
> select key from src order by key limit 10;
> 1. current
> ExtractOperator: 3 forwarded 500 rows
> LimitOperator: 4 forwarded 10 rows
> 2. early skipping
> ExtractOperator: 3 forwarded 12 rows
> LimitOperator: 4 forwarded 10 rows
> {noformat}
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