From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
---|---|
To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Cc: | "James Pang (chaolpan)" <chaolpan(at)cisco(dot)com> |
Subject: | Re: extended statistics n-distinct on multiple columns not used when join two tables |
Date: | 2023-06-13 11:25:53 |
Message-ID: | CAApHDvrMuVgDOrmg_EtFDZ=AOovq6EsJNnHH1ddyZ8EqL4yzMw@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-performance |
(moving to -hackers)
On Tue, 13 Jun 2023 at 21:30, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> út 13. 6. 2023 v 11:21 odesílatel James Pang (chaolpan) <chaolpan(at)cisco(dot)com> napsal:
>> When join two table on multiple columns equaljoin, rows estimation always use selectivity = multiplied by distinct multiple individual columns, possible to use extended n-distinct statistics on multiple columns?
>>
>> PG v14.8-1, attached please check test case with details.
>
> There is not any support for multi tables statistic
I think it's probably worth adjusting the docs to mention this. It
seems like it might be something that could surprise someone.
Something like the attached, maybe?
David
Attachment | Content-Type | Size |
---|---|---|
mention_ext_stats_dont_work_for_joins.patch | application/octet-stream | 769 bytes |
From | Date | Subject | |
---|---|---|---|
Next Message | Pavel Stehule | 2023-06-13 11:28:34 | Re: extended statistics n-distinct on multiple columns not used when join two tables |
Previous Message | Ranier Vilela | 2023-06-13 11:21:20 | Re: Avoid unncessary always true test (src/backend/storage/buffer/bufmgr.c) |
From | Date | Subject | |
---|---|---|---|
Next Message | Pavel Stehule | 2023-06-13 11:28:34 | Re: extended statistics n-distinct on multiple columns not used when join two tables |
Previous Message | Pavel Stehule | 2023-06-13 09:29:49 | Re: extended statistics n-distinct on multiple columns not used when join two tables |