On Thu, Jul 29, 2010 at 5:03 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> OK. I think you're misinterpreting the point of that comment, which >> may mean that it needs some clarification. By "the two byte header >> format is also used", I think I really meant "the header (and in fact >> the entire value) is just 2 bytes". Really, the low order bits have >> neither the old interpretation nor the new interpretation: they don't >> have any interpretation at all - they're completely meaningless. >> That's what the part after the word "but" was intended to clarify. >> Every routine in numeric.c checks for NUMERIC_IS_NAN() and gives it >> some special handling before doing anything else, so NUMERIC_WEIGHT() >> and NUMERIC_DSCALE() are never called in that case. > > I would suggest the comment ought to read something like > > NaN values also use a two-byte header (in fact, the > whole value is always only two bytes). The low order bits of > the header word are available to store dscale, though dscale > is not currently used with NaNs.
I can do something along those lines, though I'm reluctant to mention dscale specifically since we have no agreement that such a thing makes sense, or is the only/best use for those bits. Did you look at the patch to move the numeric stuff out of the .h file that I attached a few emails back? If that looks OK, I can commit it and then redo the rest of this along the lines we've discussed. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
