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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2120) auto convert map join may miss good candidates
Date Wed, 20 Apr 2011 06:34:05 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021990#comment-13021990
] 

Namit Jain commented on HIVE-2120:
----------------------------------

+1

> auto convert map join may miss good candidates
> ----------------------------------------------
>
>                 Key: HIVE-2120
>                 URL: https://issues.apache.org/jira/browse/HIVE-2120
>             Project: Hive
>          Issue Type: Bug
>            Reporter: He Yongqiang
>            Assignee: He Yongqiang
>         Attachments: HIVE-2120.1.patch
>
>
> In case in a join, there is a subquery which does a simple select, the auto convert map
join may miss a good candidate at run time. The plan generated is correct, but the selection
at runtime has a bug.
> For example:
> set hive.smalltable.filesize=1000;
> create table src_one as select * from src where key=100;
> select count(1)
> from 
> (
> select * from src
> ) subq 
> join 
> src_small on src.key = subq.key;
> The table src_small can be a small table. This is in the plan, but at runtime it gets
filtered out.

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