sub-second epoch precision

I couldn't find a nice way to turn a timestamp into a sub-second epoch value. What I came up with was:

sys.epoch(t) * 1000000 + cast((("second"(t) - floor("second"(t)))) * 1000000 as int)

Most functions seem to treat seconds as the lowest unit, e.g. extract(seconds...) and time_to_str

Is there a better option that I'm missing?

Thanks, Karl