Re: strange EO inheritance issue
Re: strange EO inheritance issue
- Subject: Re: strange EO inheritance issue
- From: Ken Anderson <email@hidden>
- Date: Fri, 04 Aug 2006 06:38:01 -0400
Patrick,
The performance problem would be related to fetching EO's at the
super-entity level. I would expect it to perform additional selects
on the extra table when doing those fetches.
To be honest, I was more thinking of all 8 tables using horizontal or
vertical inheritance. After re-reading your message, it probably
would not be as big of a problem as I had thought with 7 of the 8
using a single table.
Ken
On Aug 3, 2006, at 10:32 PM, Patrick Robinson wrote:
Ken,
I'm having a little trouble figuring out what the performance
problems might be. Wouldn't it depend on the access patterns? In
this app, each A object belongs to a different user, and they
create shared C objects, which are associated with the A's via B.
Just because one type of C corresponds to an association via a type
of B which happens to be stored in a separate B table... I dunno,
it doesn't seem like a problem to me. What am I not considering?
But.... that said, I think your suggestion of putting the extra
columns in a separate table with a relationship to it from the 8th
subclass is an excellent one. I should've thought of that!
Thanks,
- Patrick
On Aug 3, 2006, at 5:15 PM, Ken Anderson wrote:
Patrick,
Not to rain on your parade, but this is probably going to be a
performance nightmare (even if you get it to work right).
I would suggest putting those extra columns in a separate table,
putting a relationship to it in the 8th subclass, and setting a
nice batch fault number on it. I bet you it will perform WAY better.
Ken
On Aug 3, 2006, at 5:05 PM, Patrick Robinson wrote:
I've got a rather strange EO inheritance question. I've got a
situation where I've set up single-table inheritance (with a
subclass "type" column) for 7 out of 8 of my subclasses; and a
separate table (with the same "type" column) that has a bunch
more columns for the 8th, just because I didn't want all those
columns sitting there empty for most of the rows (i.e. for the
other 7 subclasses). Probably false economy, but be that as it
may....
My structure looks like this:
A <-->> B <<--> C
C is modeled as an inheritance hierarchy using horizontal
mapping, and B is modeled as the inheritance hierarchy described
above, using mostly single-table mapping. There is a different
subclass of B for each corresponding subclass of C.
It all built just fine, but when it came time to save an object
of my new C subclass (the one that corresponds to the B subclass
with its own table), the primary key of the C subclass object did
not propagate to the B subclass object -- it was left as null.
This is done with Oracle, so there's an Oracle sequence C_SEQ
that's used to obtain C's primary key, and C_ID is the primary
key of all C subclasses. Normally, this propagates to the B
subclass objects just fine (with all the other B subclasses, that
is), but it isn't working with the B subclass that is set in
EOModeler to use its own table.
Has anyone else tried to do this kind of thing, or am I just
trying to do something idiotic? :-)
--
Patrick Robinson
AHNR Info Technology, Virginia Tech
email@hidden
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