|From:||Andres Freund <andres(at)anarazel(dot)de>|
|To:||Bruce Momjian <bruce(at)momjian(dot)us>|
|Cc:||"David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>|
|Subject:||Re: doc: New cumulative stats subsystem obsoletes comment in maintenance.sgml|
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I had missed David's original email on this topic...
On 2022-07-14 18:58:09 -0400, Bruce Momjian wrote:
> On Wed, Apr 20, 2022 at 04:40:44PM -0700, David G. Johnston wrote:
> > The new cumulative stats subsystem no longer has a "lost under heavy load"
> > problem so that parenthetical should go (or at least be modified).
> > These stats can be reset so some discussion about how the system uses them
> > given that possibility seems like it would be good to add here. I'm not sure
> > what that should look like though.
> > diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
> > index 04a04e0e5f..360807c8f9 100644
> > --- a/doc/src/sgml/maintenance.sgml
> > +++ b/doc/src/sgml/maintenance.sgml
> > @@ -652,9 +652,8 @@ vacuum insert threshold = vacuum base insert threshold +
> > vacuum insert scale fac
> > tuples to be frozen by earlier vacuums. The number of obsolete tuples and
> > the number of inserted tuples are obtained from the cumulative statistics
> > system;
> > it is a semi-accurate count updated by each <command>UPDATE</command>,
> > - <command>DELETE</command> and <command>INSERT</command> operation. (It is
> > - only semi-accurate because some information might be lost under heavy
> > - load.) If the <structfield>relfrozenxid</structfield> value of the table
> > + <command>DELETE</command> and <command>INSERT</command> operation.
> > + If the <structfield>relfrozenxid</structfield> value of the table
> > is more than <varname>vacuum_freeze_table_age</varname> transactions old,
> > an aggressive vacuum is performed to freeze old tuples and advance
> > <structfield>relfrozenxid</structfield>; otherwise, only pages that have
> > been modified
> Yes, I agree and plan to apply this patch soon.
It might make sense to still say semi-accurate, but adjust the explanation to
say that stats reporting is not instantaneous?
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