From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Neil Conway <neilc(at)samurai(dot)com> |
Cc: | Warren Turkal <turkal(at)google(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: code cleanup of timestamp code |
Date: | 2008-02-26 19:55:34 |
Message-ID: | 6968.1204055734@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Neil Conway <neilc(at)samurai(dot)com> writes:
> On Tue, 2008-02-26 at 00:22 -0800, Warren Turkal wrote:
>> As a result, I have a few questions about the timestamp code. In what
>> instances is the floating point timestamp recommended?
> One circumstance is when there isn't a native int64 type available.
There are other possible reasons to prefer the float implementation;
for example it has wider range than the int64 code. Most people have
no need to represent dates beyond 6 million AD, of course, but I think
it's at least potentially useful for some scientific applications.
Also, despite the Niagara-centric moans you may have noticed from some
Sun hackers, float arithmetic is faster than int64 on quite a wide
variety of recent hardware. That may sound counterintuitive but float
units have been a traditional place to fling any surplus of gates at,
while if you don't have 64-bit hardware then int64 isn't really a native
type. MegaFLOP ratings are marketable, mega-int64-ops not so much.
(Though it's possibly true that the actual arithmetic in datetime.c is
buried under too much logic for it to make a noticeable difference :-()
Anyway I think they both have their place. int64 is a sensible default,
because it doesn't have the type of non-decimal behavior that tends
to surprise novices (compare today's bug #3991). But I don't see float
disappearing entirely.
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2008-02-26 20:03:47 | Re: pg_dump additional options for performance |
Previous Message | Simon Riggs | 2008-02-26 19:55:29 | Re: pg_dump additional options for performance |