On Sat, 10 Feb 2007, Tom Lane wrote:
> Stephan Szabo <sszabo@megazone.bigpanda.com> writes:
> > One side question is what should we do about the
> > places in the current system where it checks for the key sets being empty?
>
> I don't see that this affects that either way. I can't quite imagine
> what the semantics would be, though --- there's no such thing as a
> unique constraint with no columns, so how can there be an RI constraint
> with none?
Well, the code currently has checks with comments based on SQL3
text AFAICT. /* ---------- * SQL3 11.9 <referential constraint definition> * General rules 2)
a): * If Rf and Rt are empty (no columns to compare given) * constraint is true
if0 < (SELECT COUNT(*) FROM T) * * Note: The special case that no columns are given cannot *
occur up to now in Postgres, it's just there for * future enhancements. *
---------- */
The reason I was wondering is that it uses tgnargs == 4 as the check, and
if we change the meanings of tgnargs, we'd need to change the check.
Personally, I think we should probably just pull out the special case for
now, but thought it should be brought up.
