RI violated, bug or feature?

Hi,

my 7.0.2 runs no stable, all tests except one numerical (least
signifcant digit was off by one) ran successfull. No I did play
with RI and discovered the following:

Lets create two tables:

    test_ri=> create table publisher (name char(20));
    CREATE

    test_ri=> create index publ on publisher (name);
    CREATE

    test_ri=> create table books (title char(32), publisher char(20)
references publisher(name));
    NOTICE:  CREATE TABLE will create implicit trigger(s) for FOREIGN KEY check(s)
    CREATE

Now let's insert some data:

    test_ri=> insert into publisher (name) values ('prentice');
    INSERT 35900 1
    test_ri=> insert into publisher (name) values ('addison');
    INSERT 35901 1
    test_ri=> insert into publisher (name) values ('springer');
    INSERT 35902 1

and at least

    test_ri=> insert into books (title) values ('violated');
    INSERT 35903 1

Hey, I have now a row in books, which has no corresponding
publisher entry. Let's do another test:

    test_ri=> insert into books (title, publisher) values ('dummy', 'x');
    ERROR:  <unnamed> referential integrity violation - key referenced from books not found in publisher

Ok, that's what I expected.

    test_ri=>  insert into books (title, publisher) values ('XML handbook', 'prentice');
    INSERT 35905 1

That's ok too.

If I create table books again and add a "DEFAULT ''" clause to
column publisher then inserting rows with empty field publisher
is prohibited.

Is this a bug or is it a feature?

Martin Jacobs