Hi,
I'm probably misintepreting the documented equivalence of PERFORM and
SELECT INTO as far as the special variable FOUND is concerned, but the
following 2 definitions do not seem to produce the same result.
create table blup ( t1 text, t2 text );
create function blup_unique2 (text,text) returns boolean as 'begin
perform (select 1 from blup where t1=$1 or t1=$2 or t2=$1 or t2=$2 or
$1=$2 limit 1); return NOT FOUND; end' LANGUAGE plpgsql;
create function blup_unique3 (text,text) returns boolean as 'declare x
record; begin select into x 1 from blup where t1=$1 or t1=$2 or t2=$1 or
t2=$2 or $1=$2 limit 1; return NOT FOUND; end' LANGUAGE plpgsql;
The first will always produce false, i.e. apparently the subquery used
by PERFORM will not set the variable FOUND as expected. Is this correct?
(btw.: I'm trying a few ways to ensure that all values in both t1 and t2
are unique:
alter table blup add constraint check (blup_unique3(t1,t2)); - perhaps there are more elegant ways, any suggestions?)
Regards, Marinos
