Re: xact_start for walsender & logical decoding not updated
От | Tomas Vondra |
---|---|
Тема | Re: xact_start for walsender & logical decoding not updated |
Дата | |
Msg-id | 20191228233433.gi3er4mvdghia64v@development обсуждение исходный текст |
Ответ на | Re: xact_start for walsender & logical decoding not updated (Alvaro Herrera <alvherre@2ndquadrant.com>) |
Ответы |
Re: xact_start for walsender & logical decoding not updated
|
Список | pgsql-hackers |
On Fri, Dec 27, 2019 at 04:46:18PM -0300, Alvaro Herrera wrote: >On 2019-Dec-13, Kyotaro Horiguchi wrote: > >> At Fri, 13 Dec 2019 13:05:41 +0800, Craig Ringer <craig@2ndquadrant.com> wrote in >> > On Wed, 11 Dec 2019 at 02:08, Alvaro Herrera <alvherre@2ndquadrant.com> >> > wrote: >> > >> > > On 2019-Dec-10, Tomas Vondra wrote: >> > > >> > > > On Tue, Dec 10, 2019 at 09:42:17AM +0900, Kyotaro Horiguchi wrote: >> > > > > At Tue, 10 Dec 2019 00:44:09 +0100, Tomas Vondra < >> > > tomas.vondra@2ndquadrant.com> wrote in >> > > >> > > > > I'm not sure how much xact_start for walsender is useful and we really >> > > > > is not running a statement there. Also autovac launcher starts >> > > > > transaction without a valid statement timestamp perhaps for the same >> > > > > reason. >> > > > >> > > > Maybe, but then maybe we should change it so that we don't report any >> > > > timestamps for such processes. >> > > >> > > Yeah, I think we should to that. >> > Agreed. Don't report a transaction start timestamp at all if we're not in a >> > read/write txn in the walsender, which we should never be when using a >> > historic snapshot. >> > >> > It's not interesting or relevant. > >This patch changes xact.c to avoid updating transaction start timestamps >for walsenders (maybe more commentary is desirable). I think logical >decoding is just a special form of walsender and thus it would also be >updated by this patch, unless I misunderstood what Tomas explained. > It's true walsender should not be doing any read-write transactions or executing statements (well, maybe a decoding plugin could, but using historic snapshot). So I agree not leaving xact_start for walsender processes seems OK. >> > Reporting the commit timestamp of the current or last-processed xact would >> > likely just be confusing. I'd rather see that in pg_stat_replication if >> > we're going to show it, that way we can label it usefully. >> >> Sounds reasonable. > >Developers interested in this feature can submit a patch, as usual :-) > ;-) regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
В списке pgsql-hackers по дате отправления: