I'm actually somewhat opposed to flattening in any situation but when
it comes to M-to-M
my justification is more performance related than anything else. I
actually omit joins from
the model in certain situations to avoid unwanted fetches and
flattening is more of a recipe
for disaster than a simple join is. If you're working with a small
data set then none of this is
a big deal but once you get up into 10's of millions of rows in any
given table then you have
to be extremely careful with the modeling in order to avoid
unexpected killer fetches.
You know what I work on and I think our challenges are somewhat
atypical. I do believe though
that they have some value as general principals because however small
your data set is
to begin with, it likely will grow over time.
Alan
On May 30, 2008, at 2:19 PM, Mike Schrag wrote:
IMHO you should never flatten a many-to-many (especially across
models).
So this is interesting ... I held this same belief for years until
about 6 months ago when Chuck convinced me that I was missing
out :) I had some silly misunderstanding of EOF caching with
respect to flattened relationships that Chuck proved was wrong.
I've since been pretty happy with them (though admittedly I've
never crossed model boundaries). I'm curious what you're reasoning
for not flattening is? Definitely it will fail across databases
boundaries (which totally makes sense), but it's not immediately
obvious that (or rather why) it would fail across model boundaries
onto the same database (assuming you have the EXACT same connection
dictionary between the two).
ms
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