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