Ran into this when upgrading from 13.11 to 15.3...
The pg_restore phase failed with "ERROR: out of shared memory", and
recommended that I increase max_locks_per_transaction. Doing so let the
process run to completion.
It took 12.5 minutes to upgrade a 13GB instance. Soon after, I upgraded a
78GB cluster, and it only took 3.1 minutes.
(Both are VMs (same number of CPUs and RAM) connected to the same SAN.)
A "pg_dump --schema-only" of the two systems shows that the small-but-slow
schema is 5.9M lines.
Is this to be expected of such a huge schema?
--
Born in Arizona, moved to Babylonia.