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

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Peter Geoghegan <peter(at)2ndquadrant(dot)com>, Ants Aasma <ants(at)cybertec(dot)at>, Greg Smith <greg(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Patch: add timing of buffer I/O requests
Date: 2012-04-25 16:47:28
Message-ID: 7950.1335372448@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Sat, Apr 14, 2012 at 10:33 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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

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