On Wed, Mar 06, 2024 at 09:05:59AM +0000, Bertrand Drouvot wrote: > Yeah, all of the above done in v3 attached.
Interesting, so this relies on the slot index to ensure the unicity of the stat entries. And if the entry pointing to this ID is updated we may refer to just incorrect data. The inconsistency you could get for the fetch and reset cases are narrow, but at least what you are proposing here would protect the index lookup until the entry is copied from shmem, so this offers a better consistency protection when querying pg_stat_get_replication_slot() on a fetch, while avoiding a reset of incorrect data under concurrent activity. In passing.. pgstat_create_replslot() and pgstat_drop_replslot() rely on the assumption that the LWLock ReplicationSlotAllocationLock is taken while calling these routines. Perhaps that would be worth some extra Assert(LWLockHeldByMeInMode()) in pgstat_replslot.c for these two? Not directly related to this problem. -- Michael
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