Ok let me try to explain this again – maybe I was not very clear at
the beginning. Sorry!
I have a class BlaInteraction which is a child of statement. Each
statement has an IList<Publication>. This relationship is also part of
the domain model to make it future proved:
public class RelationshipStatementPublication : Entity
{
public virtual Statement Statement { get; set; }
public virtual Publication Publication { get; set; }
}
In my statement mapping I have:
mapping.HasManyToMany(x =>
x.Publications).Table("RelationshipStatementPublications");
My ‘naive’ approach to map a BlaInteraction to a viewmodel and count
the number of publications for each BlaInteraction is this:
return from oi in NHibernateSession.Current.Query<BlaInteraction>()
select new BlaViewModel
{
...
NoPublications = oi.Publications.Count(),
...
};
This does not scale as hnibernate creates sql code that hydrates each
publication of each (TOP n) BlaInteraction to JUST count the number of
publications. This is what I would like to prevent as removing the
‘hydration joins’ by hand optimising the sql code scales things.
Please note that I do not want to use SQL as I am trying to use IQuery
to make use of Telerik's 'Linq-based expression engine' which
generates all the 'stuff' for filtering, paging and sorting.
Another recent (failed) attempt was this:
return from oi in NHibernateSession.Current.Query<BlaInteraction>()
select new BlaViewModel
{
...
//NoPublications =
NHibernateSession.Current.QueryOver<BlaInteraction>().Where(x =>
x.Statement.Id ==
oi.Id).Select(Projections.RowCount()).SingleOrDefault<int>(),
NoPublications = NHibernateSession.Current.CreateSQLQuery("select
count(distinct PublicationId) from
dbo.RelationshipStatementPublications where StatementId
= :StatementId").SetParameter("StatementId",
oi.Id).UniqueResult<int>(),
...
};
The stuff commented out works but does not make sense. I tried this
due to a recent SO comment.
Thanks.
Christian
On Sep 14, 11:08 am, Gunnar Liljas <[email protected]> wrote:
> 1. The join is correct. You ask for the number of publications belonging to
> a specific BlaInteraction. That is what the SQL expresses.
> 2. Is it really important?
> 3. If it is, add the interaction id as a readonly property on the
> publication, and query on that.
>
> /G
>
> 2011/9/9 csetzkorn <[email protected]>
>
> > Hi experts,
>
> > Could you please be so kind and have a look at this:
>
> >http://stackoverflow.com/questions/7359783/prevent-unnecessary-cross-...
>
> > Thanks.
>
> > Christian
>
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