On 10/19/2016 09:59 AM, Bruce Momjian wrote: > On Wed, Oct 19, 2016 at 09:00:06AM -0400, Robert Haas wrote: >> On Wed, Oct 19, 2016 at 8:47 AM, Bruce Momjian <br...@momjian.us> wrote: >>> On Wed, Oct 19, 2016 at 08:33:20AM -0400, Robert Haas wrote:
>>>> Actually, I think vacuum_defer_cleanup_age is, and always has been, an >>>> ugly hack. But for some people it may be the ugly hack that is >>>> letting them continue to use PostgreSQL. >>> >>> I see vacuum_defer_cleanup_age as old_snapshot_threshold for standby >>> servers --- it cancels transactions rather than delaying cleanup. >> >> I think it's the opposite, isn't it? vacuum_defer_cleanup_age >> prevents cancellations. > > Uh, vacuum_defer_cleanup_age sets an upper limit on how long, in terms > of xids, that a standby query can run before cancel, like > old_snapshot_threshold, no? After that, we can cancel standby queries. > I see hot_standby_feedback as our current behavior on the master where > we never cancel standby queries. > > To me, hot_standby_feedback extends no-cleanup-no-cancel from the > standby to the master, while vacuum_defer_cleanup_age behaves like > old_snapshot_threshold in that it causes cancel for long-running > queries. See Andres' response on this thread. He's already covered why the setting is still useful, but why we might want to remove it anyway. -- -- Josh Berkus Red Hat OSAS (any opinions are my own) -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers