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https://issues.apache.org/jira/browse/HIVE-16102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15895226#comment-15895226
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Ashutosh Chauhan commented on HIVE-16102:
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checkForNoAggr() is explicitly checking for empty grouping set. Not sure when
it was added if there was a good reason for it. Can't think of any at the
moment. But before removing that lets add a test case for it. Also there is
HIVE_GROUPING_SETS_EXPR_NOT_IN_GROUPBY(10213) Can that be removed too?
> Grouping sets do not conform to SQL standard
> --------------------------------------------
>
> Key: HIVE-16102
> URL: https://issues.apache.org/jira/browse/HIVE-16102
> Project: Hive
> Issue Type: Bug
> Components: Operators, Parser
> Affects Versions: 1.3.0, 2.2.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Critical
> Attachments: HIVE-16102.patch
>
>
> [~ashutoshc] realized that the implementation of GROUPING__ID in Hive was not
> returning values as specified by SQL standard and other execution engines.
> After digging into this, I found out that the implementation was bogus, as
> internally it was changing between big-endian/little-endian representation of
> GROUPING__ID indistinctly, and in some cases conversions in both directions
> were cancelling each other.
> In the documentation in
> https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation,+Cube,+Grouping+and+Rollup
> we can already find the problem, even if we did not spot it at first.
> {quote}
> The following query: SELECT key, value, GROUPING__ID, count(\*) from T1 GROUP
> BY key, value WITH ROLLUP
> will have the following results.
> | NULL | NULL | 0 | 6 |
> | 1 | NULL | 1 | 2 |
> | 1 | NULL | 3 | 1 |
> | 1 | 1 | 3 | 1 |
> ...
> {quote}
> Observe that value for GROUPING__ID in first row should be `3`, while for
> third and fourth rows, it should be `0`.
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