On Thu, Mar 07, 2024 at 10:57:28AM +0530, shveta malik wrote: > --It can happen in a small window in pg_stat_get_replication_slot() > when we are consuming the return values of pgstat_fetch_replslot > (using slotent).
Yeah, it is possible that what you retrieve from pgstat_fetch_replslot() does not refer exactly to the slot's content under concurrent activity, but you cannot protect a single scan of pg_stat_replication_slots as of an effect of its design: pg_stat_get_replication_slot() has to be called multiple times. The patch at least makes sure that the copy of the slot's stats retrieved by pgstat_fetch_entry() is slightly more consistent, but you cannot do better than that except if the data retrieved from pg_replication_slots and its stats are fetched in the same context function call, holding the replslot LWLock for the whole scan duration. > Do you feel that the lock in pgstat_fetch_replslot() should be moved > to its caller when we are done copying the results of that slot? This > will improve the protection slightly. I don't see what extra protection this would offer, as pg_stat_get_replication_slot() is called once for each slot. Feel free to correct me if I'm missing something. -- Michael
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