Re: [HACKERS] GUC for cleanup indexes threshold.

On Tue, Jun 19, 2018 at 5:43 PM, Alexander Korotkov
<a.korotkov@postgrespro.ru> wrote:
> 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.

Right. We can add a new reloption specifying whether we use default
value of vacuum_index_cleanup_scale_factor or not but it might be
overkill.

>
>> 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.
>

Sorry, attached correct one.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center