Thread: hot_standby_feedback implementation

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? 

On Tue, Jun 15, 2021 at 5:24 PM Christophe Pettus <xof@thebuild.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

> On Jun 15, 2021, at 17:30, Peter Geoghegan <pg@bowt.ie> wrote:
> 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.

Thank you!  Attempting to track down a sudden burst of every session waiting on lock_manager LW locks, and part of that
isfinding the source of locks.