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https://issues.apache.org/jira/browse/HIVE-19326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16531703#comment-16531703
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Ashutosh Chauhan commented on HIVE-19326:
-----------------------------------------
+1
> 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, HIVE-19326.08.patch, HIVE-19326.09.patch,
> HIVE-19326.10.patch, HIVE-19326.11.patch, HIVE-19326.11.patch,
> HIVE-19326.12.patch, HIVE-19326.13.patch, HIVE-19326.13.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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