On Wed, Dec 9, 2009 at 8:17 PM, Mario Briggs <mario.bri...@in.ibm.com> wrote: > I was too harsh on the GenericKeyField. How about GenericKeyField > (length=x). I think the reason i put length in there is obvious, but i > can explain if need be.
Well, you may have to, because the reason that it doesn't need a length is also obvious, and I've already explained it. To clarify: The *only* reason that we are even talking about adding this field is because DB2 can't index on the datatype that is the natural match for a length-unlimited TextField. That means that the DB2 backend needs to be able to differentiate between text fields that are actually storing length-unlimited text, and text fields that are being used as a generic key store. Now, a field is either a generic key field, or it isn't. If it is, it needs to be able to store as generic a key as the backend will allow. Ideally, that would be an length-unlimited text field, and on SQLite, MySQL, Postgres and Oracle, it will be. However, this isn't possible on DB2; but given that text fields aren't used as primary keys in practice, a suitably long character limitation will suffice. How long? Pick a number. It doesn't matter what number you pick - DB2 is the only database that will be affected, and whatever N you pick, I will be able to produce a model with a CharField primary key with length N+1 that will break it. You just need to pick an N such that all practical use cases will be covered. Oracle's indexing imposes an implicit limit of 4000 characters; that sounds to me like as good a number as any. As far as I can make out, there is absolutely no use case for specifying a length in GenericKeyField. Feel free to let me know the flaw in my reasoning. Yours, Russ Magee %-) -- You received this message because you are subscribed to the Google Groups "Django developers" group. To post to this group, send email to django-develop...@googlegroups.com. To unsubscribe from this group, send email to django-developers+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-developers?hl=en.
