Re: BUG #2996: to_char( timestamp, 'DD-Mon-YYYY HH24:MI:SS.MS' ) reports .1000 ms

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Anthony Taylor" <tony(at)tg-embedded(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #2996: to_char( timestamp, 'DD-Mon-YYYY HH24:MI:SS.MS' ) reports .1000 ms
Date: 2007-02-14 07:54:10
Message-ID: 19218.1171439650@sss.pgh.pa.us
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"Anthony Taylor" <tony(at)tg-embedded(dot)com> writes:
> When using the "to_char" function to output timestamps, some timestamps
> report .1000 milliseconds.

Confirmed here: using your test case, successive timestamps look like

14-Feb-2007 02:44:04.998
14-Feb-2007 02:44:04.998
14-Feb-2007 02:44:04.998
14-Feb-2007 02:44:04.998
14-Feb-2007 02:44:04.999
14-Feb-2007 02:44:04.999
14-Feb-2007 02:44:04.999
14-Feb-2007 02:44:04.999
14-Feb-2007 02:44:04.999
14-Feb-2007 02:44:04.999
14-Feb-2007 02:44:04.1000
14-Feb-2007 02:44:04.1000
14-Feb-2007 02:44:04.1000
14-Feb-2007 02:44:05.000
14-Feb-2007 02:44:05.000
14-Feb-2007 02:44:05.000
14-Feb-2007 02:44:05.001
14-Feb-2007 02:44:05.001
14-Feb-2007 02:44:05.001
14-Feb-2007 02:44:05.001
14-Feb-2007 02:44:05.001

Not having looked at the code, my bet is that this occurs only without
--enable-integer-timestamps; is your installation compiled with that?

It would be interesting to check what happens at an hour or day
boundary; I suspect the roundoff problem may extend to higher units.
We've seen related bugs before :-(

regards, tom lane

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