On Mon, Jul 12, 2004 at 11:10:34AM -0400, Tom Lane wrote: > Peter Eisentraut <[EMAIL PROTECTED]> writes: > > The problem is that an interval datum already implies the units, > > so in order to allow interval * interval we would have to add a > > new type "interval squared", which would probably be considered to > > be a bit foolish. > > Not only foolish but complicated. Remember that interval internally > is "N months plus X seconds" (where N is integral but X needn't be). > To avoid losing information, a product datatype would have to look > something like "N months-squared plus X months-seconds plus Y > seconds-squared", which offers no intuition whatever about how to > operate on it. I doubt there's even a unique way to define > square-rooting this.
That's kinda what I was afraid of. If an interval were defined internally as a unique number of seconds, it would be easy. > Add on top the fact that we really need to change interval to be "M > months plus N days plus X seconds" to solve the ever-popular > daylight-savings-transition issues, and a product datatype would get > out of hand altogether. Yeah. > When I said "mash it down to seconds first", I was speaking very > literally... OK. So it looks like (oddly) interval can have a std. deviation, which is measured in seconds, but not a variance. Is that pretty close? Cheers, D -- David Fetter [EMAIL PROTECTED] http://fetter.org/ phone: +1 510 893 6100 mobile: +1 415 235 3778 Remember to vote! ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
