Re: [COMMITTERS] pgsql: Lower *_freeze_max_age minimum values.

On 2015-09-24 12:39:54 -0300, Alvaro Herrera wrote:
> Andres Freund wrote:
> > On 2015-09-24 10:37:33 -0400, Tom Lane wrote:
> > > Andres Freund <andres(at)anarazel(dot)de> writes:
>
> > > Should this patch not have also touched the per-table limits in
> > > reloptions.c?
> >
> > Hm. I guess that'd make sense. It's not really related to the goal of
> > making it realistic to test multixact/clog truncation, but it's less
> > confusing if consistent.
>
> Yeah, agreed.

Pushed. I actually noticed that the lower limit reloption
multixact_freeze_max_age in reloptions was wrong independent of recent
commits.

> > > and I found places in create_table.sgml that claim these variables can be
> > > set to zero. You didn't break that with this patch, but it's still wrong.
> >
> > Seems to have been "broken" back in 834a6da4f7 - the old table based
> > approach doesn't seem to have imposed lower limits. I'm not really sure
> > whether making the limits consistent and updating the docs or removing
> > them alltogether is the better approach.
>
> I'm surprised the error has survived this long. Without checking I
> can't say what's the best solution either, but I would opt for
> documenting the limits we have -- if we want to change them back to 0 I
> say that merits its own discussion.

How about simply removing that sentence? I.e. something like
<literal>autovacuum_freeze_max_age</> larger than the system-wide setting
- (it can only be set smaller). Note that while you can set
- <literal>autovacuum_freeze_max_age</> very small, or even zero, this is
- usually unwise since it will force frequent vacuuming.
+ (it can only be set smaller).
</para>

Greetings,

Andres Freund