Re: O(n) tasks cause lengthy startups and checkpoints

Nathan Bossart <nathandbossart(at)gmail(dot)com> writes:
> It's been a little while since I dug into this, but I do see your point
> that the wraparound risk could be higher in some cases. For example, if
> you have a billion temp files to clean up, the custodian could be stuck on
> that task for a long time. I will give this some further thought. I'm all
> ears if anyone has ideas about how to reduce this risk.

I wonder if a single long-lived custodian task is the right model at all.
At least for RemovePgTempFiles, it'd make more sense to write it as a
background worker that spawns, does its work, and then exits,
independently of anything else. Of course, then you need some mechanism
for ensuring that a bgworker slot is available when needed, but that
doesn't seem horridly difficult --- we could have a few "reserved
bgworker" slots, perhaps. An idle bgworker slot doesn't cost much.

regards, tom lane