I made this mistake once. We spent a LOT of money getting rid of them and in our case using a meaningful primary key actually stalled our business for the few months it took to get rid of them. Don't Do It!
J On Mon, Feb 2, 2009 at 6:22 AM, Pierre Lavignotte < pierre.lavigno...@gmail.com> wrote: > > 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 <ericllaza...@yahoo.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.lavigno...@gmail.com> > wrote: > > > > From: Pierre Lavignotte <pierre.lavigno...@gmail.com> > > Subject: Re: How to create Meaningful Primary Keys? > > To: user@cayenne.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.bar...@gmail.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 <nipar...@gmail.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 > > <nipar...@gmail.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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
