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From "Zoltan Haindrich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-19326) stats auto gather: incorrect aggregation during UNION queries (may lead to incorrect results)
Date Tue, 12 Jun 2018 15:40:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-19326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16509761#comment-16509761
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Zoltan Haindrich commented on HIVE-19326:
-----------------------------------------

this is odd...it seems on my system the union_fast_stats has a different result than on the
ptest server...I've rerun it a few times ....but it doesn't seem to be changing randomly....


> stats auto gather: incorrect aggregation during UNION queries (may lead to incorrect
results)
> ---------------------------------------------------------------------------------------------
>
>                 Key: HIVE-19326
>                 URL: https://issues.apache.org/jira/browse/HIVE-19326
>             Project: Hive
>          Issue Type: Bug
>          Components: Statistics
>            Reporter: Sergey Shelukhin
>            Assignee: Zoltan Haindrich
>            Priority: Critical
>         Attachments: HIVE-19326.01wip01.patch, HIVE-19326.02.patch, HIVE-19326.03.patch,
HIVE-19326.04.patch, HIVE-19326.05.patch, HIVE-19326.06.patch, HIVE-19326.06wip01.patch, HIVE-19326.06wip02.patch,
HIVE-19326.06wip03.patch, HIVE-19326.06wip04.patch, HIVE-19326.06wip05.patch, HIVE-19326.07.patch
>
>
> Found when investigating the results change after converting tables to MM, turns out
the MM result is correct but the current one is not.
> The test ends like so:
> {noformat}
> desc formatted small_alltypesorc_a;
> ANALYZE TABLE small_alltypesorc_a COMPUTE STATISTICS;
> desc formatted small_alltypesorc_a;
> insert into table small_alltypesorc_a select * from small_alltypesorc1a;
> desc formatted small_alltypesorc_a;
> {noformat}
> The results from the descs in the golden file are:
> {noformat}
> 	COLUMN_STATS_ACCURATE	{\"BASIC_STATS\":\"true\"}
> 	numFiles            	1                   
> 	numRows             	5                               
> ...
> 	COLUMN_STATS_ACCURATE	{\"BASIC_STATS\":\"true\"}
> 	numFiles            	1                   
> 	numRows             	15                                
> ...
> 	COLUMN_STATS_ACCURATE	{\"BASIC_STATS\":\"true\"}
> 	numFiles            	2                   
> 	numRows             	20                              
> {noformat}
> Note the result change after analyze - the original nomRows is inaccurate, but  BASIC_STATS
is set to true.
> I am assuming with metadata only optimization this can produce incorrect results.



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