Re: PITR potentially broken in 9.2

I wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
>> On 2012-12-05 17:24:42 +0000, Simon Riggs wrote:
>>> So ISTM that we should make recoveryStopsHere() return false while we
>>> are inconsistent. Problems solved.

>> I prefer the previous (fixed) behaviour where we error out if we reach a
>> recovery target before we are consistent:

> I agree. Silently ignoring the user's specification is not good.
> (I'm not totally sure about ignoring the pause spec, either, but
> there is no good reason to change the established behavior for
> the recovery target spec.)

On further thought, it seems like recovery_pause_at_target is rather
misdesigned anyway, and taking recovery target parameters from
recovery.conf is an obsolete API that was designed in a world before hot
standby. What I suggest people really want, if they're trying to
interactively determine how far to roll forward, is this:

(1) A recovery.conf parameter that specifies "pause when hot standby
opens up" (that is, as soon as we have consistency).

(2) A SQL command/function that releases the pause mode *and* specifies
a new target stop point (ie, an interactive way of setting the recovery
target parameters). The startup process then rolls forward to that
target and pauses again.

(3) A SQL command/function that releases the pause mode and specifies
coming up normally, ie not following the archived WAL any further
(I imagine this would force a timeline switch).

The existing "pause now" function could still fit into this framework;
but it seems to me to have mighty limited usefulness, considering the
speed of WAL replay versus human reaction time.

regards, tom lane