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