Alvaro Herrera <alvherre@commandprompt.com> writes:
> As for signalling, maybe we could implement something like we do for the
> postmaster signal stuff: the requestor stores a dbid in shared memory
> and sends a SIGUSR2 to pgstat or some such.
No, no, no. Martin already had a perfectly sane design for that
direction of signalling: send a special stats message to the collector.
That can carry whatever baggage it needs to. It's the reverse direction
of "the data you requested is available now, sir" that is tricky.
And I fear that having to keep track of multiple stats-collector output
files would make it very significantly trickier --- both for the stats
collector's own bookkeeping and for the signaling mechanism itself.
I don't believe it's gonna be worth that.
regards, tom lane