On 3 June 2010 02:06, Bruce Momjian <br...@momjian.us> wrote: >> Also, foreign keys can't be defined that refer to a deferrable primary >> key. That isn't mentioned at all in the manual with regard to the >> DEFERRABLE clause, though it is mentioned in the FK section. You get >> this error message >> ERROR: cannot use a deferrable unique constraint for referenced table >> >> The use case for this feature looks a little narrow at present. Can we >> do something about usability? > > Not sure why that was a limitation. >
That's in accordance with the SQL spec. I didn't think of this case originally, but all sorts of complications would arise if we were to allow FKs to refer to deferrable PKs. For example, if there are 2 temporarily duplicated PKs, and you update one of them, what would the FK's ON UPDATE actions do? I'm not convinced there is any sensible answer to this question. Regards, Dean -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
