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https://issues.apache.org/jira/browse/HIVE-17617?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16197325#comment-16197325
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Jesus Camacho Rodriguez commented on HIVE-17617:
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[~kgyrtkirk], I guess when we were finding the grouping for {{()}} in the
grouping sets before, we were setting the {{numReducers}} value to {{1}} in
ReduceSinkDesc? Are we doing the same?
Otherwise, how were we doing it before?
> Rollup of an empty resultset should contain the grouping of the empty
> grouping set
> ----------------------------------------------------------------------------------
>
> Key: HIVE-17617
> URL: https://issues.apache.org/jira/browse/HIVE-17617
> Project: Hive
> Issue Type: Sub-task
> Components: SQL
> Reporter: Zoltan Haindrich
> Assignee: Zoltan Haindrich
> Attachments: HIVE-17617.01.patch, HIVE-17617.03.patch,
> HIVE-17617.04.patch
>
>
> running
> {code}
> drop table if exists tx1;
> create table tx1 (a integer,b integer,c integer);
> select sum(c),
> grouping(b)
> from tx1
> group by rollup (b);
> {code}
> returns 0 rows; however
> according to the standard:
> The <empty grouping set> is regarded as the shortest such initial sublist.
> For example, “ROLLUP ( (A, B), (C, D) )”
> is equivalent to “GROUPING SETS ( (A, B, C, D), (A, B), () )”.
> so I think the totals row (the grouping for {{()}} should be present) - psql
> returns it.
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