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If a partition undergoes DETACH CONCURRENTLY immediately followed by DROP, this could cause a problem for a concurrent transaction recomputing the partition descriptor when running a prepared statement, because it tries to dereference a pointer to a tuple that's not found in a catalog scan. The existing retry logic added in commitdbca3469ebis sufficient to cope with the overall problem, provided we don't try to dereference a non-existant heap tuple. Arguably, the code in RelationBuildPartitionDesc() has been wrong all along, since no check was added in commit898e5e3290against receiving a NULL tuple from the catalog scan; that bug has only become user-visible with DETACH CONCURRENTLY which was added in branch 14. Therefore, even though there's no known mechanism to cause a crash because of this, backpatch the addition of such a check to all supported branches. In branches prior to 14, this would cause the code to fail with a "missing relpartbound for relation XYZ" error instead of crashing; that's okay, because there are no reports of such behavior anyway. Author: Kuntal Ghosh <kuntalghosh.2007@gmail.com> Reviewed-by: Junwang Zhao <zhjwpku@gmail.com> Reviewed-by: Tender Wang <tndrwang@gmail.com> Discussion: https://postgr.es/m/18559-b48286d2eacd9a4e@postgresql.org