Comments on: Summer of NHibernate Session 11 Screencast: Techniques for Modeling Inheritance in the Database is now available http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/ Miscellaneous musings on life, .NET development, and related things that don't really matter Thu, 17 May 2012 21:14:59 +0000 http://wordpress.org/?v=2.7 hourly 1 By: Chev http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-17787 Chev Mon, 29 Jun 2009 16:17:34 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-17787 Mapping file attached: Mapping file attached:

]]> By: Chev http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-17786 Chev Mon, 29 Jun 2009 16:14:47 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-17786 Steve Thanks once again for taking the time to do these sessions. As great as nhibernate is, there is a learning curve! I have a question regarding multiple levels of inheritance. I have a FinTransaction abstract class modeling financial transactions. I have a derived class called Refunds that model relevant Refund info. I have another derived abstract class that models Payments. Payments has subclasses like CCPayment, CashPayment etc I have started off with table per subclass and can map the FinTransaction & Refund sublass fine. How does one map the Payment abstract class and relevant subclasses? Class diagram attached here: http://blackdiamonddev.com/fin.png Any help greatly appreciated as I am going buts here :-) Steve

Thanks once again for taking the time to do these sessions. As great as nhibernate is, there is a learning curve!

I have a question regarding multiple levels of inheritance. I have a FinTransaction abstract class modeling financial transactions.

I have a derived class called Refunds that model relevant Refund info. I have another derived abstract class that models Payments. Payments has subclasses like CCPayment, CashPayment etc

I have started off with table per subclass and can map the FinTransaction & Refund sublass fine. How does one map the Payment abstract class and relevant subclasses?

Class diagram attached here:
http://blackdiamonddev.com/fin.png

Any help greatly appreciated as I am going buts here :-)

]]> By: Recent Faves Tagged With "techniques" : MyNetFaves http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-14988 Recent Faves Tagged With "techniques" : MyNetFaves Tue, 12 May 2009 10:05:11 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-14988 [...] by westernsuffolkboces | 6 days ago Web Analytics First saved by smartia | 6 days ago Summer of NHibernate Session 11 Screencast: Techniques for ... First saved by TakaSohma1 | 8 days ago Fewer Natural Oils Means Drier Skin First saved by [...] [...] by westernsuffolkboces | 6 days ago Web Analytics First saved by smartia | 6 days ago Summer of NHibernate Session 11 Screencast: Techniques for … First saved by TakaSohma1 | 8 days ago Fewer Natural Oils Means Drier Skin First saved by [...]

]]> By: Recent Links Tagged With "exceptions" - JabberTags http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-8831 Recent Links Tagged With "exceptions" - JabberTags Wed, 21 Jan 2009 22:34:22 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-8831 [...] public links >> exceptions Summer of NHibernate Session 11 Screencast: Techniques for ... Saved by jenadamz on Fri 09-1-2009 Built in Exceptions you should use Saved by grumpygrim on Fri [...] [...] public links >> exceptions Summer of NHibernate Session 11 Screencast: Techniques for … Saved by jenadamz on Fri 09-1-2009 Built in Exceptions you should use Saved by grumpygrim on Fri [...]

]]> By: Corey http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-792 Corey Wed, 03 Sep 2008 04:22:23 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-792 That did the trick, thanks. I did however end up choosing to use a one-to-one relationship rather than inheritance, purely because I didn't really like having to evict my entity and then perform the promotion. Luckily the compromise still seems pretty consistent with the domain and doesn't feel like a compromise. Thanks again for the help. That did the trick, thanks. I did however end up choosing to use a one-to-one relationship rather than inheritance, purely because I didn’t really like having to evict my entity and then perform the promotion. Luckily the compromise still seems pretty consistent with the domain and doesn’t feel like a compromise. Thanks again for the help.

]]> By: sbohlen http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-769 sbohlen Tue, 02 Sep 2008 20:00:33 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-769 @Ray: I didn't have time to cover using abstract base classes or interfaces as the root of the inheritance hierarchy in the screencast but read comment #7 above (apply the abstract="true" attribute to the superclass mapping tag) for a beginning of where to look for anwers to this one. @Ray:

I didn’t have time to cover using abstract base classes or interfaces as the root of the inheritance hierarchy in the screencast but read comment #7 above (apply the abstract=”true” attribute to the superclass mapping tag) for a beginning of where to look for anwers to this one.

]]> By: Ray http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-762 Ray Tue, 02 Sep 2008 16:15:30 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-762 Great session Steve demonstrating the two inheritance implementations! I didn't see any reference to supporting Abstract classes. I have a series of ???Type classes that inherit from an abstract BaseType class, which is simply a data abstraction of the properties in common with all of my ???Type derived classes. I thought I would use the table-per-subclass strategy, but how can I map the abstract class so that nHibernate will not be expecting an underlying table for the BaseType abstract class? Thanks, -- Ray Great session Steve demonstrating the two inheritance implementations! I didn’t see any reference to supporting Abstract classes. I have a series of ???Type classes that inherit from an abstract BaseType class, which is simply a data abstraction of the properties in common with all of my ???Type derived classes. I thought I would use the table-per-subclass strategy, but how can I map the abstract class so that nHibernate will not be expecting an underlying table for the BaseType abstract class?

Thanks,

– Ray

]]> By: sbohlen http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-732 sbohlen Mon, 01 Sep 2008 23:33:05 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-732 @JAmes: I agree that I was leaving the impression that table-per-class-hierarchy was the more performant approach (and I still think it *usually* is) but your example definitely points out a very real scenario for which it might very well not be. I also agree that non-null constraints SHOULD be surfaced in the database (usually in addition to their being modeled in the domiain classes) and this is generally why I tend to prefer the table-per-subclass approach as it tends to feel more natural to me (e.g., most like I would be inclined to model things if I weren't using NHibernate). Thanks again for the continued comments~! @JAmes:

I agree that I was leaving the impression that table-per-class-hierarchy was the more performant approach (and I still think it *usually* is) but your example definitely points out a very real scenario for which it might very well not be.

I also agree that non-null constraints SHOULD be surfaced in the database (usually in addition to their being modeled in the domiain classes) and this is generally why I tend to prefer the table-per-subclass approach as it tends to feel more natural to me (e.g., most like I would be inclined to model things if I weren’t using NHibernate).

Thanks again for the continued comments~!

]]> By: James http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-731 James Mon, 01 Sep 2008 23:04:30 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-731 @Steve: Thanks for the responses. I agree that the classes should provide handling of nulls, i.e. implement the rules around the properties etc - It's just nice to have such constraints in the database too, for reasons like defensive programming and revealing intent etc. I appreciate that the performance topic is certainly not a simple one - I really only mentioned it here, as I got the impression (rightly or wrongly) from the screen-cast that the table per hierarchy approach was being described as the more performant one, which seemed like an over-simplification, as there are probably scenarios when that wouldn't be the case. @Steve:

Thanks for the responses.

I agree that the classes should provide handling of nulls, i.e. implement the rules around the properties etc - It’s just nice to have such constraints in the database too, for reasons like defensive programming and revealing intent etc.

I appreciate that the performance topic is certainly not a simple one - I really only mentioned it here, as I got the impression (rightly or wrongly) from the screen-cast that the table per hierarchy approach was being described as the more performant one, which seemed like an over-simplification, as there are probably scenarios when that wouldn’t be the case.

]]> By: sbohlen http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/comment-page-1/#comment-712 sbohlen Mon, 01 Sep 2008 13:43:41 +0000 http://unhandled-exceptions.com/blog/index.php/2008/08/29/summer-of-nhibernate-session-11-screencast-techniques-for-modeling-inheritance-in-the-database-is-now-available/#comment-712 @Corey: that method signature should be just... public PreferredCustomer PromoteToPreferred() ...with no passed in Customer instance since this method is actually *IN* the Customer class and so of course can just operate on its own instance of Customer :) @Corey:

that method signature should be just…

public PreferredCustomer PromoteToPreferred()

…with no passed in Customer instance since this method is actually *IN* the Customer class and so of course can just operate on its own instance of Customer :)

]]>