Hi, Satyanarayana! On Wed, Apr 15, 2026 at 9:44 AM SATYANARAYANA NARLAPURAM <[email protected]> wrote: > GetCurrentLSNForWaitType() for WAIT_LSN_TYPE_STANDBY_WRITE and > WAIT_LSN_TYPE_STANDBY_FLUSH previously relied on the WAL receiver's > tracked write/flush positions (GetWalRcvWriteRecPtr/GetWalRcvFlushRecPtr). > There are two scenarios where WAIT FOR LSN queries can be stalled though > replay is making progress. Breaking it down to two to give clarity on setups > but > the underlying problem is the same. > > There are two scenarios here: > > (1). When the standby is disconnected from the primary and switched to WAL > archive mode, it continues to be in that mode until no more WAL is available > to replay > and then switch to streaming mode. Until then WAIT FOR LSN calls get stuck on > the > standby though replay catches up beyond the stale WAL receiver position. > Switching > XLog source from archive to streaming is separately tracked in [1]. > > (2). In the case of Archive recovery, no WAL receiver process exists, so these > functions return InvalidXLogRecPtr (0/0). WAIT FOR LSN with standby_flush or > standby_write modes would always time out, even for WAL that has been > fully replayed. > > Fix by falling back to the replay LSN (GetXLogReplayRecPtr) when the WAL > receiver position is invalid or behind replay. This is correct because any > WAL that has been replayed has necessarily already been written and flushed > to disk. Attached the repro test case.
Please, check, similar patch is already posted here. https://www.postgresql.org/message-id/CABPTF7Ukk8iJF7TpnK2mFOaboNJgWL1csfXu4e3J4GT0o7x0GQ%40mail.gmail.com ------ Regards, Alexander Korotkov Supabase
