On 2017-11-05 17:38:39 -0500, Robert Haas wrote: > On Sun, Nov 5, 2017 at 5:17 AM, Lucas <luca...@gmail.com> wrote: > > The patch creates a "--lock-early" option which will make pg_dump to issue > > shared locks on all tables on the backup TOC on each parallel worker start. > > That way, the backup has a very small chance of failing. When it does, > > happen in the first few seconds of the backup job. My backup scripts (not > > included here) are aware of that and retries the backup in case of failure. > > I wonder why we don't do this already ... and by default.
Well, the current approach afaics requires #relations * 2 locks, whereas acquiring them in every worker would scale that with the number of workers. IIUC the problem here is that even though a lock is already held by the main backend an independent locker's request will prevent the on-demand lock by the dump worker from being granted. It seems to me the correct fix here would be to somehow avoid the fairness logic in the parallel dump case - although I don't quite know how to best do so. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
