| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Christophe Pettus <xof(at)thebuild(dot)com> |
| Cc: | "pgsql-generallists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: hot_standby_feedback implementation |
| Date: | 2021-06-16 00:30:52 |
| Message-ID: | CAH2-Wzkjz8kKPpje5oX29Of=vUkHZNi2nXsWmsP586pndbNzqA@mail.gmail.com |
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| Lists: | pgsql-general |
On Tue, Jun 15, 2021 at 5:24 PM Christophe Pettus <xof(at)thebuild(dot)com> wrote:
> When a replica sends a hot_standby_feedback message to the primary, does that create an entry in the primary's lock table, or is it flagged to autovacuum some other way?
It pretty much works by making the WAL sender process on the primary
look like it holds a snapshot that's as old as the oldest snapshot on
the replica.
A replica can block VACUUM on the primary *directly* by holding a
table-level lock, though in practice only when somebody on the replica
acquires an AccessExclusiveLock -- which is presumably rare in
practice.
--
Peter Geoghegan
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