Re: [HACKERS] GUC for cleanup indexes threshold.

On Tue, Jun 19, 2018 at 11:34 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> On Mon, Jun 18, 2018 at 1:56 PM, Alexander Korotkov
> > So, I'm proposing to raise maximum valus of
> > vacuum_cleanup_index_scale_factor to DBL_MAX.  Any objections?
> >
>
> I agree to expand the maximum value. But if users don't want index
> cleanup it would be helpful if we have an option (e.g. setting to -1)
> to disable index cleanup while documenting a risk of disabling index
> cleanup. It seems to me that setting very high values means the same
> purpose.

Yes, providing an option to completely disable b-tree index cleanup
would be good.  But the problem is that we already use -1 value for
"use the default" in reloption.  So, if even we will make -1 guc
option to mean "never cleanup", then we still wouldn't be able to make
reloption to work this way.  Probably, we should use another "magical
value" in reloption for "use the default" semantics.

> Also, your patch lacks documentation update.

Good catch, thank you.

> BTW, I realized that postgresql.conf.sample doesn't have
> vacuum_cleanup_index_scale_factor option. Attached patch fixes it.

It seems that you post a wrong attachment, because the patch you sent
is exactly same as mine.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company