pg.ddx.io pgsql-bugs@postgresql.org mailing list archive
help / color / mirror / Atom feedBUG #18758: Incorrect query result caused by ROLLUP operation
2+ messages / 2 participants
[nested] [flat]
* BUG #18758: Incorrect query result caused by ROLLUP operation
@ 2024-12-30 16:03 PG Bug reporting form <noreply@postgresql.org>
0 siblings, 1 reply; 2+ messages in thread
From: PG Bug reporting form @ 2024-12-30 16:03 UTC (permalink / raw)
To: pgsql-bugs@lists.postgresql.org; +Cc: vectorplanck@gmail.com
The following bug has been logged on the website:
Bug reference: 18758
Logged by: Pisces Mar.
Email address: vectorplanck@gmail.com
PostgreSQL version: 17.2
Operating system: window10
Description:
create table t1 (c1 char(50));
create table t2 (c1 integer);
select t1.c1 from t2, t1 group by rollup(t1.c1); -- actual: {null},
expected: {}
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: BUG #18758: Incorrect query result caused by ROLLUP operation
@ 2024-12-30 19:11 Tom Lane <tgl@sss.pgh.pa.us>
parent: PG Bug reporting form <noreply@postgresql.org>
0 siblings, 0 replies; 2+ messages in thread
From: Tom Lane @ 2024-12-30 19:11 UTC (permalink / raw)
To: vectorplanck@gmail.com; +Cc: pgsql-bugs@lists.postgresql.org
PG Bug reporting form <noreply@postgresql.org> writes:
> create table t1 (c1 char(50));
> create table t2 (c1 integer);
> select t1.c1 from t2, t1 group by rollup(t1.c1); -- actual: {null},
> expected: {}
This is the correct result AFAICS. Per [1], ROLLUP(t1.c1) is a
shorthand for
GROUPING SETS (
( t1.c1 ),
( )
)
So first you get the output that would correspond to GROUP BY t1.c1,
and with no values of t1.c1 that output is indeed empty. But then
you get the output for an empty grouping set, which is defined in the
same place as
An empty grouping set means that all rows are aggregated down to a
single group (which is output even if no input rows were present),
as described above for the case of aggregate functions with no
GROUP BY clause.
So a single row with a null value for t1.c1 is expected, even when
the FROM clause produces no rows.
regards, tom lane
[1] https://www.postgresql.org/docs/current/queries-table-expressions.html#QUERIES-GROUPING-SETS
^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2024-12-30 19:11 UTC | newest]
Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2024-12-30 16:03 BUG #18758: Incorrect query result caused by ROLLUP operation PG Bug reporting form <noreply@postgresql.org>
2024-12-30 19:11 ` Tom Lane <tgl@sss.pgh.pa.us>
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox