"The problem we're facing is that one of the classes uses a *<component> *mapping for a property, while another derivee uses a *many-to-one* for the same property."
The DB can be old but I would know why/when you need an Entity with its ID as a component. I have used a similar trick but with a read-only view and was a very ugly quick solution done 4 years ago. Believe me that is not a good idea especially if you are doing it with a read-write entity and/or with the cache enabled... compared the QueryOver "problem" is nothing. On Wed, May 4, 2011 at 7:42 PM, lege <[email protected]> wrote: > Yes Fabio, same property of the same type. It's a legacy database > schema and it's pretty much impossible to change right now. > > On May 4, 11:12 pm, Fabio Maulo <[email protected]> wrote: > > "The problem we're facing is that one of the classes uses a > > *<component> *mapping > > for a property, while another derivee uses a *many-to-one* for the same > > property." > > > > Same property of the same Type ? > > > > On Wed, May 4, 2011 at 4:57 PM, Andrei Alecu <[email protected] > >wrote: > > > > > > > > > > > > > > > > > > > > > Hello all, > > > > > We heavily use inheritance in our data layer, almost every class we > have is > > > inherited from a base class and there are several derivees. > > > > > Recently we tried to move a pretty big dynamic HQL query that was > getting > > > out of hand and was resulting in a lot of code duplication. > > > > > The problem we're facing is that one of the classes uses a *<component> > *mapping > > > for a property, while another derivee uses a *many-to-one* for the same > > > property. > > > > > Because of QueryOver needing explicit joins to be defined, I can't seem > to > > > easily create just one query that applies to both classes. Trying to > define > > > a JoinAlias() for the <component> relationship results in an error, and > > > queries for the derivee with many-to-one don't work without a > JoinAlias(). > > > It seems awkward to need to adapt my data access code based on the way > the > > > property is defined in the mapping, and seems like a leaky abstraction > API > > > design issue. > > > > > I was able to work around this with some very ugly helper methods that > > > return various *System.Linq.Expressions.Expression<Func<* return types > > > based on which class is being worked on. > > > > > Here's some code: > > > > > Derivee1Repository.cs: > > > > > protected virtual > System.Linq.Expressions.Expression<Func<TDerivee, object>> > CategoryNameExpression() > > > { > > > return p => CategoryAlias.CategoryName; // for the > many-to-one > > > } > > > > > Derivee2Repository.cs: > > > > > protected virtual > System.Linq.Expressions.Expression<Func<TDerivee, object>> > CategoryNameExpression() > > > { > > > return p => p.Category.CategoryName; // for the component, > can't use CategoryAlias here, it will throw an exception that Derivee does > not contain a property called CategoryName > > > } > > > > > Then the joint DeriveeRepositoryBase.cs could do, for example: > > > > > query.Select(CategoryNameExpression()) > > > > > Also, another problem seems to be that casts on aliases do not seem to > work > > > at all: > > > > > Derivee1Repository.cs: > > > > > query.JoinAlias(p => p.BillingInfo, () => BillingInfoAlias); // > separate table > > > > > query.JoinAlias(() => BillingInfoAlias.PaymentMethod, () => > PaymentMethodAlias); > > > > > Derivee2Repository.cs: > > > > > query.JoinAlias(() => p.BillingInfo.PaymentMethod, () => > PaymentMethodAlias); // here billinginfo is just a component of the same > table: > > > > > DeriveeRepositoryBase.cs: > > > > > > query.Select(()=>((CreditCard)PaymentMethodAlias).ExpirationDate); > > > // exception, Derivee does not contain property called ExpirationDate > > > query.Select(()=>PaymentMethodAlias.Id); // Id is defined on > base, > > > this works > > > > > I wasn't able to use Projections.Property() either as a parameter for > the > > > method, unless someone can help with an idea on how to do the cast. > > > > > It would be nice if there was a way for JoinAlias() to work with (or > > > silently ignore) components as well, allowing an alias to be defined > and > > > used the same as if it was a separate table. *OR*, even better would be > if > > > there was a way for QueryOver to allow Linq-like auto-joins of tables > if > > > they're needed. That would simplify our code tremendously. > > > > > Ideally, I'd use Nhibernate linq for this, which does not have any of > these > > > problems as far as I can tell but I need to call a custom function that > is > > > specified in our custom Dialect, and I wasn't able to find how to call > a > > > custom function with nhibernate linq (if it's at all possible). > > > > > So, to recap, the questions are: > > > 1) Is the QueryOver behavior going to be fixed? Are there any plans on > > > making it more like linq and not requiring explicit joins for > everything? > > > It's tedious and requires intimate knowledge of how mappings are > defined, > > > which breaks abstraction layers. > > > 2) Any clues on the cast issue? > > > 3) Is it possible to use nhibernate linq to call a custom function > defined > > > in the dialect? (it's a custom AddDays(prop1, prop2) function that we > need, > > > were both prop1 and prop2 are columns in the table) > > > > > Thanks, > > > Andrei > > > > > -- > > > You received this message because you are subscribed to the Google > Groups > > > "nhusers" group. > > > To post to this group, send email to [email protected]. > > > To unsubscribe from this group, send email to > > > [email protected]. > > > For more options, visit this group at > > >http://groups.google.com/group/nhusers?hl=en. > > > > -- > > Fabio Maulo > > -- > You received this message because you are subscribed to the Google Groups > "nhusers" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/nhusers?hl=en. > > -- Fabio Maulo -- You received this message because you are subscribed to the Google Groups "nhusers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nhusers?hl=en.
