RE: sql execution time in pg_stat_statements

-----Message d'origine-----
De : Julien Rouhaud <rjuju123@gmail.com>
Envoyé : vendredi 10 septembre 2021 07:18
À : Michel SALAIS <msalais@msym.fr>
Cc : postgres performance list <pgsql-performance@postgresql.org>
Objet : Re: sql execution time in pg_stat_statements

On Fri, Sep 10, 2021 at 2:49 AM Michel SALAIS <msalais@msym.fr> wrote:
>
> I think that total_time in pg_stat_statements is cpu time + possible waits. So, can I say that:
>
> Total_sql_time = total_time + blk_read_time + blk_write_time
>
> Documentation is not clear at all on that.

In version 12 and below, total_time is the elapsed time between the execution start and stop, so it includes all
underlyingevents. That includes any IO activity, wait events or nested statements (if pg_stat_statemetns.track is set
toall).  This corresponds to the new total_exec_time field in version 13 and later. 


> Just to say that for PostgreSQL 13, total_time is replaced by “total_exec_time + total_plan_time”

Indeed, as this version also tracks planning activity.
--------------------------------------------------------------------------------
Hi,

I thaught that total_time (total_exec_time + total_plan_time) included I/O but when we have blk_read_time +
blk_write_time equals several times total_time it is difficult to continue to think that... 

So What is really total_time (total_exec_time + total_plan_time) ?