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https://issues.apache.org/jira/browse/HIVE-1194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12840807#action_12840807
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Namit Jain commented on HIVE-1194:
----------------------------------
PREHOOK: query: select /*+mapjoin(a,b)*/ * from smb_bucket_1 a right outer join
smb_bucket_2 b on a.key \
= b.key right outer join smb_bucket_3 c on b.key=c.key
PREHOOK: type: QUERY
PREHOOK: Input: defa...@smb_bucket_2
PREHOOK: Input: defa...@smb_bucket_3
PREHOOK: Input: defa...@smb_bucket_1
PREHOOK: Output:
file:/Users/heyongqiang/Documents/workspace/Hive-Test/build/ql/scratchdir/hive_2010-03-\
02_16-29-16_626_5515675647620051128/10000
POSTHOOK: query: select /*+mapjoin(a,b)*/ * from smb_bucket_1 a right outer
join smb_bucket_2 b on a.key\
= b.key right outer join smb_bucket_3 c on b.key=c.key
POSTHOOK: type: QUERY
POSTHOOK: Input: defa...@smb_bucket_2
POSTHOOK: Input: defa...@smb_bucket_3
POSTHOOK: Input: defa...@smb_bucket_1
POSTHOOK: Output:
file:/Users/heyongqiang/Documents/workspace/Hive-Test/build/ql/scratchdir/hive_2010-03\
-02_16-29-16_626_5515675647620051128/10000
NULL NULL NULL NULL 4 val_4
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
Even this one looks wrong - can you take a look in detail ?
> 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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