Re: Improve docs for n_distinct_inherited
| От | David G. Johnston |
|---|---|
| Тема | Re: Improve docs for n_distinct_inherited |
| Дата | |
| Msg-id | CAKFQuwYo6o0AY-EvnndHnVALY8dqo+mZo1rprUoZH_xyTe381g@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Improve docs for n_distinct_inherited (David Rowley <dgrowleyml@gmail.com>) |
| Список | pgsql-hackers |
On Wed, May 7, 2025 at 11:41 PM David Rowley <dgrowleyml@gmail.com> wrote:
On Thu, 8 May 2025 at 15:23, David G. Johnston
<david.g.johnston@gmail.com> wrote:
> Not liking the proposal, not sure it is even correct. Somehow "children of inheritance parent tables" are omitted.
I don't see the quoted text anywhere in this area, so I'm not sure I
follow what you mean with the omission.
Omitted from your v1 patch.
The two options for sample
sets are 1) stainherits==true and 2) stainherits==false. With
inheritance parent tables, ANALYZE gathers both sets and records both
sets in pg_statistic.
I was missing this key piece of knowledge which invalidated my entire attempt.
Here's an attempt at shortening this now that I understand the mechanics better.
Separate options exist because an inheritance parent table has two
different sets of statistics: one considering only itself and one which
also includes its children (<literal>n_distinct_inherited</literal>).
Partitioned tables, which only have rows in the children, likewise uses
the inherited option while everyone else uses <literal>n_distinct</literal>.
different sets of statistics: one considering only itself and one which
also includes its children (<literal>n_distinct_inherited</literal>).
Partitioned tables, which only have rows in the children, likewise uses
the inherited option while everyone else uses <literal>n_distinct</literal>.
David J.
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