Re: [HACKERS] GUC for cleanup indexes threshold.

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.

I've not reviewed the code deeply yet but the regression test of this
> patch seems to wrongly pass the regression tests and bt_metap()
> function of pageinspect needs to be updated.


Right.  Thank you for fixing this issue.


> Attached an updated patch
> fixed these issue. Will review the patch again.


Thank you!

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