On 9/22/25 23:15, Andrei Lepikhov wrote:
> 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.
Yes, from what I understood of the documentation [1], this is exactly
what I would like!
> 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.
For what it's worth, I've never encountered a case in my life as a
PostgreSQL support engineer where the 'dependency' kind could be useful.
I only successfully used the 'mcv' kind once (and that was only
partially successful, as it fixed the estimates but not the plan).
[1]
https://learn.microsoft.com/en-us/sql/t-sql/statements/create-statistics-transact-sql?view=sql-server-ver17#c-use-create-statistics-to-create-filtered-statistics
