Re: Patch: add timing of buffer I/O requests

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Peter Geoghegan <peter@2ndquadrant.com>, Ants Aasma <ants@cybertec.at>, Greg Smith <greg@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2012-04-25T16:47:28Z
Lists: pgsql-hackers
Robert Haas <robertmhaas@gmail.com> writes:
> On Sat, Apr 14, 2012 at 10:33 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> There's no particular reason to think that Moore's Law is going to
>> result in an increase in the fractional precision of timing data.
>> It hasn't done so in the past, for sure.

> Perhaps, but nobody's explained what we gain out of NOT using numeric.
>  "It's slow" doesn't impress me; selecting from a system view doesn't
> need to be lightning-fast.

Well, how about "the code is going to be quite a lot less readable"?
C can manipulate floats natively, but not numerics.

Also, as was pointed out upthread, the underlying data in shared memory
is almost certainly never going to be infinite-precision; so using
numeric in the API seems to me to be more likely to convey a false
impression of exactness than to do anything useful.

> However, the main thing here is that we need to do *something* here...

Agreed, this has got to be pushed forward.

			regards, tom lane