| From: | Andrei Lepikhov <lepihov(at)gmail(dot)com> |
|---|---|
| To: | Frédéric Yhuel <frederic(dot)yhuel(at)dalibo(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "pgsql-performance(at)lists(dot)postgresql(dot)org" <pgsql-performance(at)lists(dot)postgresql(dot)org>, Jehan-Guillaume de Rorthais <jgdr(at)dalibo(dot)com>, Christophe Courtois <christophe(dot)courtois(at)dalibo(dot)com>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
| Subject: | Re: Indexes on expressions with multiple columns and operators |
| Date: | 2025-09-22 21:15:52 |
| Message-ID: | 9756a3e9-5dea-4506-a077-72a4d9c302df@gmail.com |
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| Lists: | pgsql-performance |
On 22/9/2025 18:09, Frédéric Yhuel wrote:
> On 9/22/25 15:57, Andrei Lepikhov wrote:
> I wonder if we could devise another kind of extended statistic that
> would provide these "partitioned statistics" without actually partitioning.I'm not sure I fully understand your case, but SQL Server demonstrates
an interesting approach: they have a WHERE clause attached to
statistics. So, having implemented this, you may separate the whole
range of values inside the table into 'partitions' by such a WHERE
condition.
It may solve at least one issue with the 'dependencies' statistics: a
single number describing the dependency between any two values in the
columns often leads to incorrect estimations, as I see.
--
regards, Andrei Lepikhov
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