On Tue, Apr 21, 2026 at 7:03 AM Xuneng Zhou <[email protected]> wrote: > > On Tue, Apr 21, 2026 at 2:46 AM Alexander Korotkov <[email protected]> > wrote: > > > The updated patchset is attached. It includes improved coverage as > > suggested by Andres upthread. And documentation that WAIT FOR LSN is > > timeline-blind (per off-list discussion with Xuneng). > > I revised the test patch 6 to make the new cases check the intended > WAIT FOR behavior more directly, and to avoid cases where the test > could pass for the wrong reason. > > The fresh walreceiver restart test now distinguishes what we can > observe from what is only covered indirectly. > 'pg_last_wal_receive_lsn()' reports 'flushedUpto', not 'writtenUpto', > so the test now describes that state accurately and covers > 'writtenUpto' through the 'standby_write' result. This seems > appropriate to me since the two positions are seeded in the places and > conditions. Test for flush lsn should also help verify write lsn. > > The fencepost tests were split by the actual frontier being tested. > 'standby_replay' uses 'pg_last_wal_replay_lsn()', while > 'standby_flush' uses 'pg_last_wal_receive_lsn()'. This avoids treating > a replay-derived LSN as if it were also the exact write/flush > boundary. I left 'standby_write' out of the exact fencepost helper > because its frontier is not SQL-visible once walreceiver is stopped. > The async wakeup case now starts the waiter while replay is still > paused, so it must actually sleep before replay and walreceiver are > allowed to advance. > > The cascading timeline-switch test now checks the 'WAIT FOR ... > NO_THROW' status from background psql stdout. The previous log-marker > pattern could pass after unexpected returned status, includingn > 'timeout', because the following statement would still run. The > 'received_tli > 1' check remains, but only as confirmation that the > downstream followed the new timeline; the 'success' status proves the > wait completed as intended. > > Please check it.
LGTM, I've added some comments for new functions in 0006. I propose to push this patchset. Probably something is still missing and we will have to go back to this. But it seems to make a lot of aspects much better. ------ Regards, Alexander Korotkov Supabase
v7-0002-Fix-memory-ordering-in-WAIT-FOR-LSN-wakeup-mechan.patch
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v7-0005-Wake-standby_write-standby_flush-waiters-from-the.patch
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v7-0004-Use-replay-position-as-floor-for-WAIT-FOR-LSN-sta.patch
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v7-0003-Remove-redundant-WAIT-FOR-LSN-caller-side-pre-che.patch
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v7-0001-Use-barrier-semantics-when-reading-writing-writte.patch
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v7-0006-Improve-WAIT-FOR-LSN-test-coverage.patch
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v7-0007-Document-that-WAIT-FOR-LSN-is-timeline-blind.patch
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