RE: [OJB-developers] multiple classes mapped to single table requ est for comments

[Matthew B. <ma...@so...>]

Yah I figured #2 was the better was of doing it, I'm mostly done the
implementation now.

I assume for joined tables we don't need to add the class discriminator
since that relationship shouldn't have been able to be created in the first
place if the class type was wrong.

I thought about using IN, but doesn't that have a length limit? Maybe that's
not important for extents (people should inherit THAT much :))

m

-----Original Message-----
From: Oleg Nitz [mailto:on...@uk...] 
Sent: Sunday, June 09, 2002 12:43 PM
To: obj...@li...
Subject: Re: [OJB-developers] multiple classes mapped to single table
request for comments

On Sunday 09 June 2002 19:27, Matthew Baird wrote:
> 2. Change the select queries for classes that have the 'ojbConcreteClass'
> column mapped to append a where discriminator based on classtype. So a
> query for all D in the above example would include the following WHERE
> clause
>
> 	WHERE MultiTable.CLASS_TYPE='D' OR MultiTable.CLASS_TYPE='B'
>
> 	PROS: Most efficient. No checking necessary to see if the
> materialized object is an instance of what was requested. Iterators Would
> only contain valid candidates and thus size and other methods would work
as
> expected.
> 	CONS: Bigger change, more change to SQL generation code; where
> clause would be slower?
+1 for #2

BTW you might use the shorter syntax 
    WHERE MultiTable.CLASS_TYPE IN ('B','D')

Oleg




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