On Thu, May 09, 2024 at 12:51:32AM +0300, Alexander Korotkov wrote:
> > > However, parent's table extended statistics already covers all its
> > > children.
> >
> > => That's the wrong explanation. It's not that "stats on the parent
> > table cover its children". It's that there are two types of stats:
> > stats for the "table hierarchy" and stats for the individual table.
> > That's true for single-column stats as well as for extended stats.
> > In both cases, that's indicated by the inh flag in the code and in the
> > catalog.
> >
> > The right explanation is that extended stats on partitioned tables are
> > not similar to indexes. Indexes on parent table are nothing other than
> > a mechanism to create indexes on the child tables. That's not true for
> > stats.
> >
> > See also my prior messages
> > ZiJW1g2nbQs9ekwK@pryzbyj2023
> > Zi5Msg74C61DjJKW@pryzbyj2023
>
> Yes, I understand that parents pg_statistic entry with stainherit ==
> true includes statistics for the children. I tried to express this by
> word "covers". But you're right, this is the wrong explanation.
>
> Can I, please, ask you to revise the patch?
I tried to make this clear but it'd be nice if someone (Tomas/Alvaro?)
would check that this says what's wanted.
--
Justin