> Do poeple agree w/ me here?
I do !
All my tables have an autogenerated integer ID. I just need to read it to
point a specific row but I do NOT define it in Cayenne Modeler because
(until now) each time you have to re-engineer you DB schema you lose all the
fields you have manually designed and I don't want these fields to be
writable.
Cheers
Cordialement,
Pierre Lavignotte
Ingénieur Conception & Développement
http://pierre.lavignotte.googlepages.com
On Mon, Feb 2, 2009 at 3:15 PM, Eric Lazarus <ericllazaru..ahoo.com> wrote:
> I can't let this point(er) go buy: JUST SAY NO TO MEANINGFUL POINTERS!
>
> There are BIG problems with having meaningful primary keys in general in
> terms of keeping your program growing and useful long term. When you can
> avoid it, avoid it... and when YOU are designing the underlying database
> from scratch, I think you can almost always avoid it. Putting meaning in the
> pointers is often the reason that a system needs to be re-written or pitched
> and replaced.
>
> A client of mine had to replace an existing application because they had
> used four budget product codes as part of a pointer field and could no
> longer represent the number of products in four digits. Cost huge $ to
> upgrade to SAP...
>
> Here is another example, a bad choose made by apple early on, putting data
> into what amounts to a pointer:
>
> http://en.wikipedia.org/wiki/Mac_OS_memory_management
>
> So, now it seems that the name and DOB of each person is not going to
> change. Later it turns out that they do change under some situations and now
> you have to write big hacks to deal with it.
>
> Just say no to meaning in pointers! Keep pointers STUPID! Meaningless bit
> squences make great pointers in OO programs. That's my view.
>
> Of course rules are made to be broken and, when the DB exists already and
> is used by a big pile of existing code, you likely have no choice but in
> other situations, try to avoid meaningfulness in pointers.
>
> Do poeple agree w/ me here?
>
> Eric
> +1 (917) 589-6579
>
> --- On Mon, 2/2/09, Pierre Lavignotte <pierre.lavignott..mail.com> wrote:
>
> From: Pierre Lavignotte <pierre.lavignott..mail.com>
> Subject: Re: How to create Meaningful Primary Keys?
> To: use..ayenne.apache.org
> Date: Monday, February 2, 2009, 8:28 AM
>
> I don't think his question is about sequence usage but about selecting rows
> with specific PK values...
>
> Cordialement,
> Pierre Lavignotte
> Ingénieur Conception & Développement
> http://pierre.lavignotte.googlepages.com
>
>
> On Mon, Feb 2, 2009 at 2:25 PM, Alessio Giovanni Baroni <
> alessiogiovanni.baron..mail.com> wrote:
>
> > It's all ok. But, you are sure that in Entity screen, you are selected
> > "Custom Sequence" on the "PK Generation Strategy"?
> > If you do it, AND you add a filed relative to a pk column, you can
> handling
> > the keys, without the cayenne's control.
> >
> > Hi.
> >
> >
> > 2009/2/2 Νίκος Παράσχου <niparas..mail.com>
> >
> > > First of all thank you for your replies.
> > >
> > > I have the following table:
> > >
> > > Vehicle (
> > > plate_num CHAR(10) NOT NULL,
> > > mixed_weight DOUBLE PRECISION NOT NULL,
> > > type CHAR(30) NOT NULL,
> > > manufacturer CHAR(20),
> > > PRIMARY KEY (plate_num)
> > > )
> > >
> > > In Cayenne Modeller I have the dbEntity "vehicle" with all
> the above
> > > attributes (plate_num is check as PK). There is also the objEntity
> > > "Vehicle" with all the above attributes except the PK
> (plate_num).
> > >
> > > I want to select the type of the vehicle with plate_num =
> "AHZ-4141".
> > >
> > > Could you please post some code samples? I have tried so many things
> > > (with DataObjectUtils too) but still no success.
> > >
> > > Thank you,
> > > Nikos
> > >
> > > Στις 02-02-2009, ημέρα Δευ, και ώρα 12:49 +0100,
> ο/η Pierre Lavignotte
> > > έγραψε:
> > > > Hi Nikos,
> > > >
> > > > If you need PK for all your tables, then maybe you need to
> generate
> > them.
> > > > But if you only need to use them for a couple tables then you
> should
> > look
> > > at
> > > > DataObjectUtils class.
> > > >
> > > >
> > > > Cheers,
> > > > Pierre
> > > >
> > > > Cordialement,
> > > > Pierre Lavignotte
> > > > Ingénieur Conception & Développement
> > > > http://pierre.lavignotte.googlepages.com
> > > >
> > > >
> > > > On Mon, Feb 2, 2009 at 12:35 PM, Νίκος Παράσχου
> <niparas..mail.com>
> > > wrote:
> > > >
> > > > > Hello,
> > > > >
> > > > > It is the first time I am using cayenne and I have some
> questions
> > > > > regarding the primary keys.
> > > > >
> > > > > What I want to do is select some rows of a table where the
> PK has a
> > > > > specific value. The problem is I can't access the PK. I
> can specify
> > > > > qualifiers only with the non-PK columns. The PKs I am using
> have some
> > > > > meaning (they are not just numbers) so it is very important
> to be
> > able
> > > > > to use them.
> > > > >
> > > > > How can I add the PK to the fields of the Object Entities?
> > > > >
> > > > > In this page
> > > http://cayenne.apache.org/doc20/primary-key-generation.html
> > > > > the answer is to create a Meaningful Primary Key.
> > > > >
> > > > > How can I create Meaningful Primary Keys?
> > > > >
> > > > > Are there any security issues when using Meaningful Primary
> Keys?
> > > > >
> > > > > Thank you for your time,
> > > > > Nikos
> > > > >
> > > > >
> > >
> > >
> >
>
>
>
>
This archive was generated by hypermail 2.0.0 : Mon Feb 02 2009 - 09:23:16 EST