Re: [doc] plan invalidation when statistics are update

On 2020/11/18 11:04, torikoshia wrote:
> Hi,
>
> AFAIU, when the planner statistics are updated, generic plans are invalidated and PostgreSQL recreates. However, the manual doesn't seem to explain it explicitly.
>
>   https://www.postgresql.org/docs/devel/sql-prepare.html
>
> I guess this case is included in 'whenever database objects used in the statement have definitional (DDL) changes undergone', but I feel it's hard to infer.
>
> Since updates of the statistics can often happen, how about describing this case explicitly like an attached patch?

+1 to add that note.

- statement. Also, if the value of <xref linkend="guc-search-path"/> changes
+ statement. For example, when the planner statistics of the statement
+ are updated, <productname>PostgreSQL</productname> re-analyzes and
+ re-plans the statement.

I don't think "For example," is necessary.

"planner statistics of the statement" sounds vague? Does the statement
is re-analyzed and re-planned only when the planner statistics of database
objects used in the statement are updated? If yes, we should describe
that to make the note a bit more explicitly?

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION