Re: Remove vacuum_defer_cleanup_age

On Wed, Oct 19, 2016 at 08:33:20AM -0400, Robert Haas wrote:
> On Tue, Oct 18, 2016 at 4:33 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> > Based on that argument, we would never be able to remove any
> > configuration parameter ever.
>
> Well... no. Based on that argument, we should only remove
> configuration parameters if we're fairly certain that they are not
> useful any more, which will be rare, but is not never. I agree that
> *if* vacuum_defer_cleanup_age is no longer useful, it should be
> removed. I'm just not convinced that it's truly obsolete, and you
> haven't really offered much of an argument for that proposition. It
> does something sufficiently different from hot_standby_feedback that
> I'm not sure it's accurate to say that one can substitute for the
> other, and indeed, I see Andres has already suggested some scenarios
> where it could still be useful.
>
> 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.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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