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From "John Pullokkaran" <jpullokka...@hortonworks.com>
Subject Re: Review Request 40589: Implement limit push down through union all in CBO
Date Fri, 18 Dec 2015 23:23:37 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/40589/#review111311
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ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveSortUnionReduceRule.java
(line 84)
<https://reviews.apache.org/r/40589/#comment171432>

    The real value of pushing limit past union is to push it further down (by pushing it past
sel, join).
    
    If the sortrel ended up just below union & if sortrel also had sort in it (i.e if
union's input is synthetic limit) then i think we should remove it.
    
    May be we should enhance HiveSortRemoveRule to look for pattern SortRel-union-SortRel
and remove synthetic SortRel below union if it has sort in it.
    
    Otherwise we end up paying double sorting cost.


- John Pullokkaran


On Dec. 17, 2015, 10:47 p.m., pengcheng xiong wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/40589/
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> 
> (Updated Dec. 17, 2015, 10:47 p.m.)
> 
> 
> Review request for hive and Ashutosh Chauhan.
> 
> 
> Repository: hive-git
> 
> 
> Description
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> 
> HIVE-11775
> 
> 
> Diffs
> -----
> 
>   common/src/java/org/apache/hadoop/hive/conf/HiveConf.java 243f281 
>   ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveSortUnionReduceRule.java
PRE-CREATION 
>   ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java 36a12bf 
>   ql/src/test/queries/clientpositive/cbo_SortUnionTransposeRule.q PRE-CREATION 
>   ql/src/test/queries/clientpositive/limit_join_transpose.q 80430c6 
>   ql/src/test/queries/clientpositive/tez_dynpart_hashjoin_3.q cecbbd7 
>   ql/src/test/results/clientpositive/cbo_SortUnionTransposeRule.q.out PRE-CREATION 
> 
> Diff: https://reviews.apache.org/r/40589/diff/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> pengcheng xiong
> 
>


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