Thanks for your information, yes, with multiple columns equal join and correlation , looks like extended statistics could help reduce “significantly rows estimation”. Hopefully it’s in future version.
James
From: Pavel Stehule <pavel.stehule@gmail.com> Sent: Tuesday, June 13, 2023 7:29 PM To: David Rowley <dgrowleyml@gmail.com> Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>; James Pang (chaolpan) <chaolpan@cisco.com> Subject: Re: extended statistics n-distinct on multiple columns not used when join two tables
On Tue, 13 Jun 2023 at 21:30, Pavel Stehule <pavel.stehule@gmail.com> wrote: > út 13. 6. 2023 v 11:21 odesílatel James Pang (chaolpan) <chaolpan@cisco.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.
