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Subject: Re: Review Request 54284: StatsOptimizer should return no rows on
 empty table with group by
From: pengcheng xiong <pxiong@hortonworks.com>
To: Ashutosh Chauhan <hashutosh@apache.org>
Cc: pengcheng xiong <pxiong@hortonworks.com>, hive <dev@hive.apache.org>
Date: Fri, 02 Dec 2016 21:55:43 -0000
Message-ID: <20161202215543.1641.78284@reviews.apache.org>
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Reply-To: pengcheng xiong <pxiong@hortonworks.com>
archived-at: Fri, 02 Dec 2016 21:55:45 -0000

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> On Dec. 2, 2016, 9:10 p.m., Ashutosh Chauhan wrote:
> > ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java, line 182
> > <https://reviews.apache.org/r/54284/diff/1/?file=1574510#file1574510line182>
> >
> >     Is there any differnce between NULL & constant? It seems you are not making use of NULL any where.

Yes, I have make use of NULL. Please See
{code}
if (getGbyKeyType(pgbyOp) == GbyKeyType.OTHER) {
          return null;
        }
        // we already check if rowCnt is null and rowCnt==0 means table is
        // empty.
        else if (getGbyKeyType(pgbyOp) == GbyKeyType.CONSTANT && rowCnt == 0) {
          return null;
        }
{code}
That means, only if it is groupby constant and rowCnt=0, we skip the StatsOptimizer.
If it is NULL, which should be the 3rd condition (if, else if, else), we continue.


- pengcheng


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https://reviews.apache.org/r/54284/#review157823
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On Dec. 2, 2016, 1:23 a.m., pengcheng xiong wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/54284/
> -----------------------------------------------------------
> 
> (Updated Dec. 2, 2016, 1:23 a.m.)
> 
> 
> Review request for hive and Ashutosh Chauhan.
> 
> 
> Repository: hive-git
> 
> 
> Description
> -------
> 
> HIVE-13452
> 
> 
> Diffs
> -----
> 
>   ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java 17510e9 
>   ql/src/test/queries/clientpositive/constGby.q PRE-CREATION 
>   ql/src/test/results/clientpositive/constGby.q.out PRE-CREATION 
> 
> Diff: https://reviews.apache.org/r/54284/diff/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> pengcheng xiong
> 
>


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