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* Incorrect sort result caused by ROLLUP and WHERE operation
@ 2025-01-02 07:28 谭忠涛 <zhongtao.tan@seaboxdata.com>
2025-01-02 10:49 ` Re: Incorrect sort result caused by ROLLUP and WHERE operation Zhang Mingli <zmlpostgres@gmail.com>
2025-01-02 16:04 ` Re: Incorrect sort result caused by ROLLUP and WHERE operation Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 2 replies; 3+ messages in thread
From: 谭忠涛 @ 2025-01-02 07:28 UTC (permalink / raw)
To: pgsql-bugs <pgsql-bugs@lists.postgresql.org>; +Cc: 谭忠涛 <zhongtao.tan@seaboxdata.com>
Case:
create table t1(a int, b int);
insert into t1 values(1,1),(1,2);
select a,b,sum(10) as s from t1 where a = 1 group by rollup(a,b) order by a, s desc;
Regards
谭忠涛 数据研究院数据库事业部
北京东方金信科技股份有限公司
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公众号：东方金信
网址：www.seaboxdata.com
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* Re: Incorrect sort result caused by ROLLUP and WHERE operation
2025-01-02 07:28 Incorrect sort result caused by ROLLUP and WHERE operation 谭忠涛 <zhongtao.tan@seaboxdata.com>
@ 2025-01-02 10:49 ` Zhang Mingli <zmlpostgres@gmail.com>
1 sibling, 0 replies; 3+ messages in thread
From: Zhang Mingli @ 2025-01-02 10:49 UTC (permalink / raw)
To: pgsql-bugs <pgsql-bugs@lists.postgresql.org>; 谭忠涛 <zhongtao.tan@seaboxdata.com>
Hi,
Zhang Mingli
www.hashdata.xyz
Do you mean order of null value (column a) is wrong?
Use NULLS FIRST/LAST to order null values.
On Jan 2, 2025 at 18:19 +0800, 谭忠涛 <zhongtao.tan@seaboxdata.com>, wrote:
>
> Case:
> create table t1(a int, b int);
> insert into t1 values(1,1),(1,2);
> select a,b,sum(10) as s from t1 where a = 1 group by rollup(a,b) order by a, s desc;
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Incorrect sort result caused by ROLLUP and WHERE operation
2025-01-02 07:28 Incorrect sort result caused by ROLLUP and WHERE operation 谭忠涛 <zhongtao.tan@seaboxdata.com>
@ 2025-01-02 16:04 ` Tom Lane <tgl@sss.pgh.pa.us>
1 sibling, 0 replies; 3+ messages in thread
From: Tom Lane @ 2025-01-02 16:04 UTC (permalink / raw)
To: 谭忠涛 <zhongtao.tan@seaboxdata.com>; +Cc: pgsql-bugs <pgsql-bugs@lists.postgresql.org>
"=?utf-8?B?6LCt5b+g5rab?=" <zhongtao.tan@seaboxdata.com> writes:
> create table t1(a int, b int);
> insert into t1 values(1,1),(1,2);
> select a,b,sum(10) as s from t1 where a = 1 group by rollup(a,b) order by a, s desc;
Yeah. This is fixed in HEAD (v18-to-be) but the fix is too invasive
to consider back-patching. Basically the problem is that older
versions don't understand that the post-ROLLUP value of "a" can be
different from the pre-ROLLUP value, so they think the "where a = 1"
clause removes any need to sort by "a".
As a workaround you could write something like "order by a+0, s desc"
to fool the optimizer into considering the ordering column to be
different from the value that's constrained by WHERE.
regards, tom lane
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2025-01-02 07:28 Incorrect sort result caused by ROLLUP and WHERE operation 谭忠涛 <zhongtao.tan@seaboxdata.com>
2025-01-02 10:49 ` Zhang Mingli <zmlpostgres@gmail.com>
2025-01-02 16:04 ` Tom Lane <tgl@sss.pgh.pa.us>
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