> On Thu, 24 Jul 2008 17:55:24 +0200, Brady Kelly
> <[EMAIL PROTECTED]> wrote:
>
> >> Could this be because you are/were working in a data centric world? I
> >> regularly see changes in database structure that do not represent
> >> changes in my domain. An example of this might be selective
> >> denormalization for optimization on a small system or the pulling out
> >> of something that was columns into a new joined table.
> >>
> >> Cheers,
> >>
> >> Greg
> >
> >Maybe with less coupling I would see more changes like that, but now that
> I
> >consider it, coupling is the reason I don't see these changes. They are
> >considered indulgent, as they would require 'unnecessary' code changes.
>
> That's an example of the push-back I talked about. Optimizations to the
> database don't take place because the code is overly coupled to it and
> that optimization to the database would require time to perform extensive
> changes to code.
I think most denormalizations don't take place for the simple reason
that it would create a big steaming pile of crap.
Denormalizations for performance are almost always for data fetches,
and then also for aggregated sets e.g. for reports. In most cases
denormalizations for these targets aren't done on the tables which are
updated, inserted for the simple fact that the code tehn also has to work with
denormalized tables.
Before someone steps in and yelps: "See! I was right", data management
on denormalized data is a pain, not because there are more fields in the
table, but because there are more rows to manage for a single entity update.
This isn't covered in most (of at all) o/r mappers and I think also in
almost no DAL. No, repositories and the like won't help here, you can't
abstract away denormalization downsides.
Frankly, reading the posts following my earlier post I still have the
idea that not everyone understood with what I said with coupling between
abstract entity E and table, and abstract entity E and class: instead, the
focus is still 'what if a table is changed' or 'what if a class is changed',
and what kind of effects that might have...
FB
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