Leon <leon@udmnet.ru> wrote:
> Earlier I proposed that links should be of type similar to tid,
> so inserts should be fed with values of tid. But this requires
> intermediate step, so there can be a function which takes primary
> key and returns tid, or as you say a function
> last_touched('other_table_name') - this seems the best choice.
Beware of adding special purpose hard-links as a way to
skip the run-time value comparisons. A link looks attractive
but it really only works for one-to-one relationships
(any multi-way relationships would require a list of links
to follow) and a link has all of the overhead that a
foreign key requires.
As somone who has developed several commercial dbms systems,
I would discourage doing a special "link" type. There are
other ways to gain performance -- de-normalize your tables
if you are doing mainly reads; carefully check your storage
layout; and, of course, buy more RAM ;-)
--
Bob Devine devine@cs.utah.edu