Обсуждение: short ciruit logic of plpgsql in 8.2
Does anyone know if logic operations in plpgsql are short circuited in 8.2? Regards, Richard Broersma Jr.
hello, it depends on SQL. plpgsql hasn't own arithmetic unit. You can test it simply: postgres=# create or replace function a() returns bool as $$ begin raise notice 'a'; return true; end$$ language plpgsql; CREATE FUNCTION postgres=# create or replace function b() returns bool as $$ begin raise notice 'a'; return true; end$$ language plpgsql; CREATE FUNCTION postgres=# select a() or b(); NOTICE: a ?column? ---------- t (1 row) result: statements are short circuited. 2007/5/17, Richard Broersma Jr <rabroersma@yahoo.com>: > Does anyone know if logic operations in plpgsql are short circuited in 8.2? > > Regards, > Richard Broersma Jr. > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Have you searched our list archives? > > http://archives.postgresql.org/ >
Richard Broersma Jr <rabroersma@yahoo.com> writes: > Does anyone know if logic operations in plpgsql are short circuited in 8.2? They are often optimized, but if you expect "short circuiting" following exactly the rules of, say, C, you are likely to be disappointed. See the manual: http://www.postgresql.org/docs/8.2/static/sql-expressions.html#SYNTAX-EXPRESS-EVAL regards, tom lane
This keeps biting me. In a trigger function for INSERT OR UPDATE if you try IF TG_OP = 'UPDATE' AND OLD.foo = 'bar' THEN ... it will blow up on inserts because there is no OLD. I always expect this to short circuit and am always disappointed. Easy fix, of course... IF TG_OP = 'UPDATE' THEN IF OLD.foo = 'bar' THEN ... In case this was what the OP was asking about in particular, it still happens to me in 8.2 - Ian On 5/17/07, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Richard Broersma Jr <rabroersma@yahoo.com> writes: > > Does anyone know if logic operations in plpgsql are short circuited in 8.2? > > They are often optimized, but if you expect "short circuiting" following > exactly the rules of, say, C, you are likely to be disappointed. See > the manual: > > http://www.postgresql.org/docs/8.2/static/sql-expressions.html#SYNTAX-EXPRESS-EVAL > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 1: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly >