On Tue, Nov 04, 2014 at 08:30:21AM +0000, Laurenz Albe wrote: > David Fetter wrote: > > On Tue, Nov 04, 2014 at 07:51:06AM +0900, Tatsuo Ishii wrote: > >> Just out of curiosity, why is Oracle's NUMBER (I assume you are > >> talking about this) so fast? > > > > I suspect that what happens is that NUMBER is stored as a native > > type (int2, int4, int8, int16) that depends on its size and then > > cast to the next upward thing as needed, taking any performance > > hits at that point. The documentation hints (38 decimal places) > > at a 128-bit internal representation as the maximum. I don't know > > what happens when you get past what 128 bits can represent. > > No, Oracle stores NUMBERs as variable length field (up to 22 bytes), > where the first byte encodes the sign and the comma position and the > remaining bytes encode the digits, each byte representing two digits > in base-100 notation (see Oracle Metalink note 1007641.6).
Thanks for clearing that up, and sorry for spreading misinformed guesses. > So it's not so different from PostgreSQL. > No idea why their arithmetic should be faster. I have an idea, but this time, I think it's right. They have at least one team of people whose job it is to make sure that it is fast. Cheers, David. -- David Fetter <da...@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fet...@gmail.com iCal: webcal://www.tripit.com/feed/ical/people/david74/tripit.ics Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
