Re: Doubts about FK

2008/9/12 Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>

> On Fri, Sep 12, 2008 at 12:14 PM, Rafael Domiciano
> <rafael(dot)domiciano(at)gmail(dot)com> wrote:
> > Hi there,
> >
> > In my DB I have a couple of FK, so the change of referenced columns is a
> > quite complicated.
> > Today, I DISABLE TRIGGER ALL on the tables envolved and then ENABLE
> TRIGGER
> > ALL to back them.
> > Is there a better way to do that?
>
> Depends. Are other people connected to the server when you do it?
> disable trigger disables the triggers for everybody, not just you if I
> remember correctly. If other folks are using the db, then they can
> insert bad data during that period.

I do it in a transaction, so there's no problem about the other folks...!

> > I read something about SET CONSTRAINTS ALL DEFFERED, but I don't know how
> to
> > use it.
>
> the constraints have to created as deferrable to do that. then, in a
> transaction, you can do something like:
>
Can I turn my FK into deferrable FK only in that transaction?

>
> begin;
> update in a way that would normally violate an FK
> insert in a way that fixes the previous statement's FK relationship
> commit;
>
> and it will work as long as the constraints all make sense by the time
> you get to commit.

That's what I wanna to do!

>
>
> Note that unique constraints are not deferrable in pgsql.
>