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Posted to dev@hive.apache.org by "Namit Jain (JIRA)" <ji...@apache.org> on 2011/04/20 08:34:05 UTC
[jira] [Commented] (HIVE-2120) auto convert map join may miss good
candidates
[ 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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