Fwd: Re: [Glorp-development] Class hierarchy mapping & queries

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Date: Wed, 13 Dec 2006 11:03:56 -0500
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From: Alan Knight <[hidden email]>
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Subject: Re: [Glorp-development] Class hierarchy mapping & queries
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That's an interesting question, and one which illustrates why I described the inheritance support as having weaknesses.  In particular, it appears that subselects to abstract classes mapped with horizontal inheritance don't work. Also, it looks like mechanisms like retrieve: don't work with horizontal inheritance. In the former case it tries to build up a query using the primary table of the abstract superclass, which doesn't have one. In the latter I think it's just that the retrieve: clauses don't get propogated to the generated sub-queries.

I think the right thing to do for this would be for the subselect to generate a compound query doing a union of required fields from each of the concrete tables. But the inheritance support predates support for unions, and it hasn't been set up to use it. This would be useful for the general case of horizontal inheritance as well.

At 04:53 AM 12/13/2006, Mark Plas wrote:

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Hi,
 
This mail is part of a set of glorp questions I have (see some other mails I've sent recently).
 
The question I would like to address here is:
 
Suppose I have a class hierarchy mapped in such a way that there is one table for each concrete class. When I do a query on the abstract superclass, Glorp will issue several sql statements and concatenate the results (I think). My question is: What happens if I have a query on the abstract superclass that itself contains a sub-select on another abstract superclass ? Will Glorp execute queries for every combination of concrete classes ? Are there limitations here ?
 
Thanks,
Mark
 
 
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