Re: Why are data types size limited?
Date: 2000/03/21
Message-ID: <8b81fr$mkj$1_at_bob.news.rcn.net>#1/1
eison_at_cc.gatech.edu wrote in message <8b63hp$91n_at_catapult.gatech.edu>...
>"Joe \"Nuke Me Xemu\" Foster" <joe_at_bftsi0.uucp> wrote:
>: It's mainly an implementation issue. The b-tree-based indexing scheme
>: most RDBMS' use works best when the b-tree nodes, including the keys,
>: fits within a disk page, however that's defined.
>
>Thank you, this seems to be pointing to the reason... more reasons would
>be lovely...
>
>: Who has
>: an email address longer than 255 characters?
>
>The point was that once you limit a field length, somebody will eventually
>come along with something longer than that field length. Say you decide
>all e-mails are 100 chars max, then some Lotus Notes user will come along
>with a 105 character address, and things break. I still don't understand
>why a database can't handle this; I would assume a slow-down on the rare
>cases where this happens would be more acceptable than an error message,
>but maybe it would be worse than just a slow-down.
>
>: Here's an example of one
>: of those tricks, in pseudo-SQL:
>: select mytable.*
>: from mytable
>: where mytable.IndexedEmailAddress = substring(:findthisaddress, 1, 255)
>: and mytable.FullEmailAddress = :findthisaddress
>
>Thanks for pointing this out. I believe it still won't deal with things
>like comments longer than Oracle's 4000 char limit (which requires you to
>switch to a different object with its own tricky weird rules for using it
>- I would think it should be a transparent-to-the-user switch, just use a
>different datatype, and unfortunately I would be wrong for thinking that).
>Additionally, I don't want to have to do this for almost every field I
>have - it seems to largely defeat the purpose of having the database in
>the first place.
>
>As an OO programmer, my intuition says that the database should be able to
>abstract these picky detail away from me so I don't have to worry about
>it. Right now I'm writing an extra layer to do it, but I really wanted to
>understand why I have to bother. I assume it's ignorance, and like the
>disk page explanation, and would love more explanations along those lines
>along with thoughts on working around them.
>
>-David
>--
>David Eison (404) 892-6579 x 212 <http://www.cc.gatech.edu/~eison>
>Brother, Phi Kappa Theta Fraternity
Received on Tue Mar 21 2000 - 00:00:00 CET