Re: [Maypole] Auto Increment Primary Keys (and Documentation)

From: Dave Howorth (dhoworth at mrc-lmb.cam.ac.uk)
Date: Thu Jan 27 2005 - 10:57:44 GMT


Gordon Haverland wrote:
> I have a couple of tables which are related, one of which has an
> auto_increment primary key. I can create a tuple (row/object) of
> data without ever mentioning this primary key as I understand
> things. Fine. But, is there some easy way to find out just what
> value was assigned to that variable? For all the power of all
> the modules behind Maypole, do I really need to search for the
> maximum value in the primary key column after I create the tuple?
> It seems to me, that if there is a high access rate on the
> application, that this isn't going to get me the primary key
> value I want anyway, some other process may have created another
> tuple in that same table between when my process created the
> tuple and when it searched to find the maximum value of the
> primary key.
>
> I would have thought this would be a common requirement, since the
> value of the primary key column in a tuple is often used as a
> foreign key in other tables. But I just don't see it anywhere.
> Are the creates for the associated tables supposed to get this
> value automagically?

Does this answer your questions?

   my $brewery = Brewery->create({
        name => 'Anheuser Busch',
   })

   print $brewery->id;

   my $beer = Beer->create({
        name => 'Budweiser',
        brewery => $brewery,
        style => 'lager',
   });

   print $beer->id;

Cheers, Dave

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