On Thu, 2005-11-03 at 10:32 -0500, Tom Lane wrote: > Bruce Momjian <pgman@candle.pha.pa.us> writes: > >> On Thu, 3 Nov 2005, Simon Riggs wrote: > >>> At the moment we've established we can do this fairly much for free. > > > Agreed. With the proposal, we are saving perhaps 5% storage space for > > numeric fields, but are adding code complexity and reducing its possible > > precision. > > Having to invent UNKNOWNNUMERIC is hardly what I'd call "for free". > That takes it out of the realm of being a small localized project. > I'd feel a lot happier about this if we could keep the dynamic range > up to, say, 10^512 so that it's still true that NUMERIC can be a > universal parse-time representation. That would also make it even > more unlikely that anyone would complain about loss of functionality. > > To do that we'd need 8 bits for weight (-128..127 for a base-10K > exponent is enough) but we need 9 bits for dscale which does not > quite fit. I think we could make it go by cramming the sign and > the high-order dscale bit into the first NumericDigit --- the > digit itself can only be 0..9999 so there are a couple of bits > to spare. This probably *would* slow down packing and unpacking of > numerics, but just by a couple lines of C. Arguably the net reduction > in I/O costs would justify that.
This sounds a much better solution and the code neater too. This still would be a very small patch, not very intrusive at all. I'll have a hack at this now. Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org