In master I've been testing some new code that I'm working on around foreign keys.
I wasn't quite sure if it was possible to include the same column twice in a foreign key, so I tested....
create table r1 (a int);
create table r2 (b int);
create unique index on r2(b,b);
alter table r1 add constraint r2_b_fkey foreign key (a,a) references r2 (b,b);
ERROR: cache lookup failed for opclass 0
Which is not quite any of the messages that I would have expected
I've tracked this down to a small bug in transformFkeyCheckAttrs() where opclasses[1] won't get set because if (attnums[0] == indexStruct->indkey.values[1]) will match then break out of the inner loop. Instead opclasses[0] gets set twice.
The attached seems to fix the problem, but the whole thing makes me wonder if this is even meant to be allowed? I was thinking that this might be a good time to disallow this altogether, since it's already broken and looks like it has been for about 11 years
Any thoughts?
Regards
David Rowley
