Re: [HACKERS] GUC for cleanup indexes threshold.

On Sat, Mar 10, 2018 at 3:40 AM, Alexander Korotkov
<a.korotkov@postgrespro.ru> wrote:
> On Fri, Mar 9, 2018 at 3:12 PM, Masahiko Sawada <sawada.mshk@gmail.com>
> wrote:
>>
>> On Fri, Mar 9, 2018 at 8:43 AM, Alexander Korotkov
>> <a.korotkov@postgrespro.ru> wrote:
>> > 2) These parameters are reset during btbulkdelete() and set during
>> > btvacuumcleanup().
>>
>> Can't we set these parameters even during btbulkdelete()? By keeping
>> them up to date, we will able to avoid an unnecessary cleanup vacuums
>> even after index bulk-delete.
>
>
> We certainly can update cleanup-related parameters during btbulkdelete().
> However, in this case we would update B-tree meta-page during each
> VACUUM cycle.  That may cause some overhead for non append-only
> workloads.  I don't think this overhead would be sensible, because in
> non append-only scenarios VACUUM typically writes much more of information.
> But I would like this oriented to append-only workload patch to be
> as harmless as possible for other workloads.

What overhead are you referring here? I guess the overhead is only the
calculating the oldest btpo.xact. And I think it would be harmless.