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Michael Paquier ab874faaa1 Ignore temporary relations in RelidByRelfilenumber() ... Temporary relations may share the same RelFileNumber with a permanent relation, or other temporary relations associated with other sessions. Being able to uniquely identify a temporary relation would require RelidByRelfilenumber() to know about the proc number of the temporary relation it wants to identify, something it is not designed for since its introduction in f01d1ae3a1. There are currently three callers of RelidByRelfilenumber(): - autoprewarm. - Logical decoding, reorder buffer. - pg_filenode_relation(), that attempts to find a relation OID based on a tablespace OID and a RelFileNumber. This makes the situation problematic particularly for the first two cases, leading to the possibility of random ERRORs due to inconsistencies that temporary relations can create in the cache maintained by RelidByRelfilenumber(). The third case should be less of an issue, as I suspect that there are few direct callers of pg_filenode_relation(). The window where the ERRORs are happen is very narrow, requiring an OID wraparound to create a lookup conflict in RelidByRelfilenumber() with a temporary table reusing the same OID as another relation already cached. The problem is easier to reach in workloads with a high OID consumption rate, especially with a higher number of temporary relations created. We could get pg_filenode_relation() and RelidByRelfilenumber() to work with temporary relations if provided the means to identify them with an optional proc number given in input, but the years have also shown that we do not have a use case for it, yet. Note that this could not be backpatched if pg_filenode_relation() needs changes. It is simpler to ignore temporary relations. Reported-by: Shenhao Wang <wangsh.fnst@fujitsu.com> Author: Vignesh C <vignesh21@gmail.com> Reviewed-By: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Reviewed-By: Takamichi Osumi <osumi.takamichi@fujitsu.com> Reviewed-By: Michael Paquier <michael@paquier.xyz> Reviewed-By: Masahiko Sawada <sawada.mshk@gmail.com> Reported-By: Shenhao Wang <wangsh.fnst@fujitsu.com> Discussion: https://postgr.es/m/bbaaf9f9-ebb2-645f-54bb-34d6efc7ac42@fujitsu.com Backpatch-through: 13		3 weeks ago
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src	Ignore temporary relations in RelidByRelfilenumber()	3 weeks ago
KNOWN_BUGS	…
MISSING_FEATURES	…
Makefile	…
TODO	Change documentation references to PG website to use https: not http:	8 years ago