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From "Amareshwari Sriramadasu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2344) filter is removed due to regression of HIVE-1538
Date Wed, 10 Aug 2011 11:44:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082293#comment-13082293
] 

Amareshwari Sriramadasu commented on HIVE-2344:
-----------------------------------------------

Sorry John. Earlier patch has a bug. 

bq. Any other filter on 'udf selected as column alias in select' will also be pushed down
always. Do we want to do this?
More on this: Here, currently the filter (along with udf) is pushed till TableScan. So essentially,
we would apply the udf twice for the qualified rows. And it is expensive, if udf is expensive.
So, I propose we should not push it beyond the select. Thoughts?

> filter is removed due to regression of HIVE-1538
> ------------------------------------------------
>
>                 Key: HIVE-2344
>                 URL: https://issues.apache.org/jira/browse/HIVE-2344
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 0.8.0
>            Reporter: He Yongqiang
>            Assignee: Amareshwari Sriramadasu
>             Fix For: 0.8.0
>
>         Attachments: hive-patch-2344.txt, ppd_udf_col.q.out.txt
>
>
>  select * from 
>  (
>  select type_bucket,randum123
>  from (SELECT *, cast(rand() as double) AS randum123 FROM tbl where ds = ...) a
>  where randum123 <=0.1)s where s.randum123>0.1 limit 20;
> This is returning results...
> and 
>  explain
>  select type_bucket,randum123
>  from (SELECT *, cast(rand() as double) AS randum123 FROM tbl where ds = ...) a
>  where randum123 <=0.1
> shows that there is no filter.

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