Re: fixing old_snapshot_threshold's time->xid mapping

On Thu, Apr 16, 2020 at 1:14 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> I still think we need a way to test this without waiting for hours to
> hit various edge cases. You argued against a fixed binning of
> old_snapshot_threshold/100 arguing its too coarse. How about a 1000 or
> so? For 60 days, the current max for old_snapshot_threshold, that'd be a
> granularity of 01:26:24, which seems fine. The best way I can think of
> that'd keep current GUC values sensible is to change
> old_snapshot_threshold to be float. Ugly, but ...?

Yeah, 1000 would be a lot better. However, if we switch to a fixed
number of bins, it's going to be a lot more code churn. What did you
think of my suggestion of making head_timestamp artificially move
backward to simulate the passage of time?

--
Robert Haas
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