Re: Avoiding roundoff error in pg_sleep()

On Thu, Sep 25, 2025 at 02:42:32PM -0400, Tom Lane wrote:
> Anyway, I propose trying to get rid of this misbehavior by avoiding
> floating point in the delay computation, as attached. With this
> patch I get less surprising behavior:
>
> [...]
>
> The code is a little more tied to TimestampTz being measured in
> microseconds than it was before, but it wouldn't really be much
> harder to fix if we ever change that.

LGTM. I considered suggesting initializing the delay before the loop and
then updating it at the end of the loop, but that moves the
CHECK_FOR_INTERRUPTS between the delay calculation and the WaitLatch(),
which seems like it might extend the sleeps a bit (although that might be
negligible in practice). Otherwise, the code seems to match
float8_timestamptz() somewhat closely, although I doubt it's worth trying
to unify the implementations.

--
nathan