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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1194) sorted merge join
Date Wed, 03 Mar 2010 19:02:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12840805#action_12840805
] 

Namit Jain commented on HIVE-1194:
----------------------------------

POSTHOOK: query: select /*+mapjoin(a,b)*/ * from smb_bucket_1 a left outer join smb_bucket_2
b on a.key \
= b.key full outer join smb_bucket_3 c on b.key=c.key
POSTHOOK: type: QUERY
POSTHOOK: Input: default@smb_bucket_2
POSTHOOK: Input: default@smb_bucket_3
POSTHOOK: Input: default@smb_bucket_1
POSTHOOK: Output: file:/Users/heyongqiang/Documents/workspace/Hive-Test/build/ql/scratchdir/hive_2010-03\
-02_16-28-56_475_666795559542199348/10000
1 val_1 NULL  NULL  NULL  NULL
3 val_3 NULL  NULL  NULL  NULL
4 val_4 NULL  NULL  NULL  NULL
NULL  NULL  NULL  NULL  4 val_4
5 val_5 NULL  NULL  NULL  NULL
10  val_10  NULL  NULL  NULL  NULL
NULL  NULL  NULL  NULL  10  val_10
NULL  NULL  NULL  NULL  17  val_17
NULL  NULL  NULL  NULL  19  val_19
NULL  NULL  NULL  NULL  20  val_20
NULL  NULL  NULL  NULL  23  val_23


same as above

> sorted merge join
> -----------------
>
>                 Key: HIVE-1194
>                 URL: https://issues.apache.org/jira/browse/HIVE-1194
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: He Yongqiang
>             Fix For: 0.6.0
>
>         Attachments: hive-1194-2010-02-28.patch, hive-1194-2010-3-2.2.patch, hive-1194-2010-3-2.patch
>
>
> If the input tables are sorted on the join key, and a mapjoin is being performed, it
is useful to exploit the sorted properties of the table.
> This can lead to substantial cpu savings - this needs to work across bucketed map joins
also.
> Since, sorted properties of a table are not enforced currently, a new parameter can be
added to specify to use the sort-merge join.

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