After some extreme hacking and debugging, the dust around the pgsql driver has finally settled. The fixes mostly concern rare conditions when the driver is being (ab)used while under heavy error rates from the database, cancelling random queries, dropping and/or destructing objects willy-nilly.
It passes all tests that I have with flying colours now, no exceptions.
People using PostgreSQL are invited to test the improved driver (both in Pike 8.0 and in Pike 8.1).