Re: Empty values of pg_stats_ext when table is empty

On Mon, Nov 1, 2021 at 01:23:01PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/14/view-pg-stats-ext.html
> Description:
>
> When table mytable is being inherited it may not contain any data but still
> return row sets from the inheriting tables. Now doing CREATE STATISTICS on
> mytable will work but won't have any values.
>
> This is very difficult to realize from a user's perspective and can be
> either considered a feature or a bug, i.e. being enhanced.
>
> Given this is considered as a feature, I suggest to add a comment at the end
> of this documentation
> https://www.postgresql.org/docs/current/view-pg-stats-ext.html like this:
>
> <<
> Note then there are no values when the table is empty which happens when
> there are tables which inherit from it.
> <<
>
> I could also think of a run-time warning?

I talked to Tomas Vondra and he says there will be proper parent
statistics in PG 15, due to be released in the next 1-2 months. Here is
the PG 15 release note item:

https://www.postgresql.org/docs/15/release-15.html

Allow extended statistics to record statistics for a parent with all its
children (Tomas Vondra, Justin Pryzby)

Regular statistics already tracked parent and parent/all-children
statistics separately.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

Indecision is a decision. Inaction is an action. Mark Batterson