246a6c8f7b
Commit dafa084, added in 10, made the removal of temporary orphaned tables more aggressive. This commit makes an extra step into the aggressiveness by adding a flag in each backend's MyProc which tracks down any temporary namespace currently in use. The flag is set when the namespace gets created and can be reset if the temporary namespace has been created in a transaction or sub-transaction which is aborted. The flag value assignment is assumed to be atomic, so this can be done in a lock-less fashion like other flags already present in PGPROC like databaseId or backendId, still the fact that the temporary namespace and table created are still locked until the transaction creating those commits acts as a barrier for other backends. This new flag gets used by autovacuum to discard more aggressively orphaned tables by additionally checking for the database a backend is connected to as well as its temporary namespace in-use, removing orphaned temporary relations even if a backend reuses the same slot as one which created temporary relations in a past session. The base idea of this patch comes from Robert Haas, has been written in its first version by Tsunakawa Takayuki, then heavily reviewed by me. Author: Tsunakawa Takayuki Reviewed-by: Michael Paquier, Kyotaro Horiguchi, Andres Freund Discussion: https://postgr.es/m/0A3221C70F24FB45833433255569204D1F8A4DC6@G01JPEXMBYT05 Backpatch: 11-, as PGPROC gains a new flag and we don't want silent ABI breakages on already released versions.
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