Re: max_standby_delay considered harmful

Robert Haas wrote:
> If you had a genuinely better idea for how this should work, I would
> be the first to endorse it, but it's becoming clear that you don't,
> which makes me also skeptical of your contention that we will be
> better off with no knob at all. I find that position not very
> plausible. Nor do I really see how this is backing us into any kind
> of a corner. If we're really concerned that we're going to suddenly
> come up with a much better method of controlling this behavior (and so
> far nobody seems close to having such a brilliant insight), then let's
> just put a note in the documentation saying that the setting has
> problems X, Y, and Z and that if we develop a better method for
> controlling this behavior, the GUC may be modified or removed in a
> future release. Ripping it out seems like a drastic overreaction,
> particularly considering that we're already in beta.
>
> This feature has been in the tree since December 19th when the initial
> Hot Standby patch was committed, and the last significant code change
> was on February 13th. It is now May 5th. The fact that you didn't
> read the patch sooner is not a reason why we should rip it out now.
> Yes, the current implementation is a little crufty and has some
> limitations. See also work_mem.

I am afraid the current setting is tempting for users to enable, but
will be so unpredictable that it will tarnish the repuation of HS and
Postgres. We don't want to be thinking in 9 months, "Wow, we shouldn't
have shipped that features. It is causing all kinds of problems." We
have done that before (rarely), and it isn't a good feeling.

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