On Fri, 21 Apr 2006, Alban Hertroys wrote:
> Stephan Szabo wrote:
> >>SQL> CREATE TABLE ltree_test (path ltree PRIMARY KEY REFERENCES
> >>ltree_test(path));
> >>NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
> >>"ltree_test_pkey" for table "ltree_test"
> >>CREATE TABLE
> >>SQL> INSERT INTO ltree_test VALUES ('a'::ltree);
> >>INSERT 84117368 1
> >>SQL> INSERT INTO ltree_test VALUES ('a.b'::ltree);
> >>INSERT 84117369 1
> >>SQL> INSERT INTO ltree_test VALUES ('a.b.c'::ltree);
> >>INSERT 84117370 1
> >>SQL> DELETE FROM ltree_test WHERE path = 'a.b'::ltree;
> >>DELETE 1
> >
> > I'm not sure why you expect this to error. Any row that would reference
> > a.b would be removed by the delete AFAICS.
>
> Nope, there's no ON DELETE CASCADE on the FK, and RESTRICT is the
> default (thankfully).
The only row that matches 'a.b' that I see in the above is the second
insert which is also the row that is deleted in the delete. And since the
constraint uses equality, any row that matches path='a.b' is a target of
the delete because it's the same operator.