| From: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
|---|---|
| To: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Function to move the position of a replication slot |
| Date: | 2017-08-17 00:19:15 |
| Message-ID: | CAMsr+YE=uquLNnSK12tmPh70qdZ2nR+u31bacJwJB_V9a1wV6Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 17 August 2017 at 07:30, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
wrote:
>
> Definitely agreed on that. Any move function would need to check if
> the WAL position given by caller is already newer than what's
> available in the local pg_wal (minimum of all other slots), with a
> shared lock that would need to be taken by xlog.c when recycling past
> segments. A forward function works on a single entry, which should be
> disabled at the moment of the update. It looks dangerous to me to do
> such an operation if there is a consumer of a slot currently on it.
>
>
pg_advance_replication_slot(...)
ERROR's on logical slot, for now. Physical slots only.
Forward-only.
Future work to allow it to use the logical decoding infrastructure to
fast-forward a slot by reading only catalog change information and
invalidations, either via a dummy output plugin that filters out all xacts,
or by lower level use of the decoding code.
Reasonable?
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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