Aaron Stone wrote:
> On Sat, 2007-07-14 at 11:09 +0200, Paul J Stevens
wrote:
>> Aaron Stone wrote:
>
>>> You can't just update the dbmail_users table to
change the user_idnr
>>> because the foreign keys in the mailboxes table
will cause the user's
>>> mailboxes to be detached and then removed.
>> Wrong, *because* of the constraints it is in fact
absolutely necessary
>> to change the user_idnr in the dbmail_users table.
It's what I do,
>> whenever I migrate to ldap. Works perfectly, but
only if you have the
>> proper constraints in place. They are part of the
default schema.
>
> I don't understand this. If there are current entries
in dbmail_users,
> and they have user_idnr's, and those are targets of a
FK in the dbmail_
> mailboxes table...
>
> CREATE TABLE dbmail_mailboxes (
> ...
> FOREIGN KEY owner_idnr_fk (owner_idnr)
> REFERENCES dbmail_users (user_idnr) ON DELETE
CASCADE ON UPDATE CASCADE
> );
>
> ....when you change the user_idnr in dbmail_users,
doesn't it cause a
> cascading delete of those entries in the mailboxes
table?
Nope. You misunderstand. If you delete a user entry, the
delete
cascades. But if you update a user entry, the update
cascades. So in
this case, if you update a user_idnr in the users table,
all
corresponding entries in the mailboxes table follow suit:
the
back-reference stays intact.
--
____________________________________________________________
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Paul Stevens paul at
nfg.nl
NET FACILITIES GROUP GPG/PGP:
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