On Tue, Mar 20, 2018 at 09:30:15PM +0100, Tomas Vondra wrote:
> On 03/20/2018 02:11 PM, Arthur Zakirov wrote:
> > max_shared_dictionaries_size is defined as PGC_SIGHUP now. Added check
> > of a new value to disallow to set zero if there are loaded dictionaries
> > and to decrease maximum allowed size if loaded size is greater than the
> > new value.
> >
>
> I wonder if these restrictions needed? I mean, why not to allow setting
> max_shared_dictionaries_size below the size of loaded dictionaries?
>
> Of course, on the one hand those restriction seem sensible. On the other
> hand, perhaps in some cases it would be useful to allow violating them?
>
> I mean, why not to simply disable loading of new dictionaries when
>
> (max_shared_dictionaries_size < loaded_size)
>
> Maybe I'm over-thinking this though. It's probably safer and less
> surprising to enforce the restrictions.
Hm, yes in some cases this check may be over-engineering. I thought that
it is reasonable and safer in v7 patch. But there are similar GUCs,
wal_keep_segments and max_wal_size, which don't do additional checks.
And people are fine with them. So I removed that check from the variable.
Please find the attached new version of the patch.
--
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company
