Re: pgbench progress with timestamp

Use milliseconds for consistency with the '%n' log_prefix patch currently
submitted by Tomas Vondra in the CF.

  sh> ./pgbench -P 1 -N -T 100 -c 2
  starting vacuum...end.
  progress: 1.0 s, 546.0 tps, lat 3.619 ms stddev 4.426
  progress: 2.0 s, 575.0 tps, lat 3.480 ms stddev 1.705

  sh> ./pgbench -P 1 --progress-timestamp -N -T 100 -c 2
  starting vacuum...end.
  progress: 1440328800.064 s, 549.0 tps, lat 3.602 ms stddev 1.698
  progress: 1440328801.064 s, 570.0 tps, lat 3.501 ms stddev 1.704

I like the idea of the timestamp.  But could just always print both the
timestamp and the elapsed time, rather than adding another switch to decide
between them?

I agree that an option for this purpose is on the heavy side.

I'm not sure how fine it would be, though: progress lines can already be a little bit long (under -R & -L) and I do not like wide terminal. Also, I see --progress as a "user friendly" easy to read feature to know how things are going during a run. A timestamp does not fall into this category: it is pretty ugly and unreadable, so it is really out of necessity that I'm resorting to that.

So I would rather keep the option because of the inelegance of having timestamps printed.