| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
| Cc: | Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>, Jean-Luc Lachance <jllachan(at)nsd(dot)ca>, "Michael S(dot) Tibbetts" <mtibbetts(at)head-cfa(dot)cfa(dot)harvard(dot)edu>, pgsql-sql(at)postgresql(dot)org |
| Subject: | Re: min() and NaN |
| Date: | 2003-07-22 19:33:19 |
| Message-ID: | 15160.1058902399@sss.pgh.pa.us |
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Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)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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