From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruce Momjian <pgman@candle.pha.pa.us>
Cc: Stephan Szabo <sszabo@megazone.bigpanda.com>
Cc: Jean-Luc Lachance <jllachan@nsd.ca>
Cc: Michael S. Tibbetts <mtibbetts@head-cfa.cfa.harvard.edu>
Cc: pgsql-sql@postgresql.org
Subject: Re: min() and NaN
Date: Tue, 22 Jul 2003 15:33:19 -0400
Message-ID: <15160.1058902399@sss.pgh.pa.us> (raw)
In-Reply-To: <200307221859.h6MIxJk11503@candle.pha.pa.us>
References: <200307221859.h6MIxJk11503@candle.pha.pa.us>
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Well, my 2 cents is that though we consider NULL when ordering via ORDER
> BY, we ignore it in MAX because it really isn't a value, and NaN seems
> to be similar to NULL.
Good idea, but I don't think we can get away with it. The spec says
that MAX/MIN have to be consistent with the comparison operators (and
therefore with ORDER BY):
iii) If MAX or MIN is specified, then the result is respec-
tively the maximum or minimum value in TXA. These results
are determined using the comparison rules specified in
Subclause 8.2, "<comparison predicate>".
NULL can be special, because it acts specially in comparisons anyway.
But NaN is just a value of the datatype.
I'd be willing to go against the spec if I thought that having
ignore-NaNs behavior was sufficiently important, but I don't think it's
important enough to disregard the spec...
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgman@candle.pha.pa.us, sszabo@megazone.bigpanda.com, jllachan@nsd.ca, mtibbetts@head-cfa.cfa.harvard.edu
Subject: Re: min() and NaN
In-Reply-To: <15160.1058902399@sss.pgh.pa.us>
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