| From: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
|---|---|
| To: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, Peter Geoghegan <pg(at)bowt(dot)ie>, Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, "Ideriha, Takeshi" <ideriha(dot)takeshi(at)jp(dot)fujitsu(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com>, pgsql-hackers-owner(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] GUC for cleanup indexes threshold. |
| Date: | 2018-03-14 04:40:03 |
| Message-ID: | CAD21AoCCObzLUxSya-KWCrRChjVvAv6v34=dQDZQmr3gbYzOkw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Mar 10, 2018 at 3:40 AM, Alexander Korotkov
<a(dot)korotkov(at)postgrespro(dot)ru> wrote:
> On Fri, Mar 9, 2018 at 3:12 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
> wrote:
>>
>> On Fri, Mar 9, 2018 at 8:43 AM, Alexander Korotkov
>> <a(dot)korotkov(at)postgrespro(dot)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.
Regards,
--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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