I'm not sure; but I vaguely remember reading in pgsql-general that the optimizer can tell if the function returns a constant, so only evaluate it once. Yup, there it is: http://archives.postgresql.org/pgsql-general/2001-03/msg01476.php If you stick with one function per constant, it should still be fast. You loose that if you go the table route, though; or even a case-type statement within function. Further details (and confirmation of statement about speed of 'constant' functions) might be obtained by posting to pgsql-general. Frank At 09:33 PM 2/4/02 +0000, Shane Wright wrote: >Hi Frank, > >Thanks, interesting idea - it looks like it would work fine, but wouldn't it >be a little on the slow side? > >I like the constant table idea (hmm, could automatically populate the >constant table by parsing my PHP definitions files, tasty...) - but again >speed is of the essence... > >-- >Shane > >On Monday 04 Feb 2002 9:12 pm, Frank Bax wrote: >> Try a pg function. >> >> http://www.postgresql.org/idocs/index.php?sql-createfunction.html >> >> CREATE FUNCTION one() RETURNS int4 >> AS 'SELECT 1 AS RESULT' >> LANGUAGE 'sql'; >> SELECT one() AS answer; >> answer >> -------- >> 1 >> >> If you are truly adventurous, you could create a 'constant' table and have >> the function take an argument, which is key to the table. >> >> Frank >> >> At 02:00 PM 2/4/02 +0000, Shane Wright wrote: >> >Hi >> > >> >This may be the wrong list to ask this, apologies if so :) >> > >> >Anyway, is there any way to define constants in PostgreSQL - my app has >> > lots of them at the PHP level, but it'd be nice to use them directly in >> > the SQL without overly complex query building. >> > >> >Something like this... >> > >> >DEFINE CONSTANT MYCONST = 4; >> > >> >SELECT * FROM mytable WHERE myfield=MYCONST; >> > >> > >> >Thanks >> > >> >-- >> >Shane
