Dominique Devienne <ddevienne@xxxxxxxxx> writes: > Hi. A tester just tried to restore two custom backups (not official > PostgreSQL ones) concurrently. > ... > The second session completed OK. > But the first session errors out with: > Error: DDL Error: GRANT USAGE ON SCHEMA "SCH1", "SCH2" TO "SCH2:RO", > "SCH2:RW", "SCH2:SU": #XX000: ERROR: tuple concurrently updated > Thus I'm trying to understand what's going on. Since both restores tried to grant some permissions on SCH1, they both had to update SCH1's pg_namespace row (specifically nspacl). We have no support for concurrent updates in the catalog-manipulation code, so if the second run arrives at that step before the first one has committed its pg_namespace change, you get this error. > Is the issue related to trying to change SCHEMA ACLs for SCH1 concurrently, > in two long running transactions? How am I supposed to resolve this? The window is probably too small to hit if each restore is committing as it goes, but if you run in --single-transaction mode then this isn't surprising. I'd say don't try to run concurrent restores. regards, tom lane
