Re: max_standby_delay considered harmful

Florian Pflug <fgp(at)phlo(dot)org> writes:
> The only remaining option is to continue applying WAL until you reach
> a point where no locks are held, then pause. But from a user's POV
> that is nearly indistinguishable from simply setting
> hot_standby_conflict_winner to in the first place I think.

Not really, the use case would be using the slave as a reporting server,
you know you have say 4 hours of reporting queries during which you will
pause the recovery. So it's ok for the pause command to take time.

What I understand the boolean option would do is to force the user into
choosing either high-availability or using the slave for other purposes
too. The problem is in wanting both, and that's what HS was meant to solve.

Having pause/resume allows for a mixed case usage which is simple to
drive and understand, yet fails to provide adaptive behavior where
queries are allowed to pause recovery implicitly for a while.

In my mind, that would be a compromise we could reach for 9.0, but it
seems introducing those admin functions now is to far a stretch. I've
been failing to understand exactly why, only getting a generic answer I
find unsatisfying here, because all the alternative paths being
proposed, apart from "improve documentation", are more involved code
wise.

Regards,
--
dim