Update: I tried the following:
public FolderHierarchyNode Get()
{
using (var s = _sessions.OpenSession())
return s.CreateQuery("select n from
FolderHierarchyNode n join fetch n._children")
.SetResultTransformer(new
global::NHibernate.Transform.DistinctRootEntityResultTransformer())
.List<FolderHierarchyNode>()
.Single(n => n.Parent.IsNull());
}
This resulted in actually twice as many queries being issued. After
reading up on DistinctRootEntityResultTransformer, I don't see how it
can achieve my desired results since the problem I'm having is that I
get multiple queries, not that I get duplicate rows as a result of a
single query.
On Aug 24, 9:43 am, philw <[email protected]> wrote:
> Hi
>
> I think this might be of some help to you, ot was for me
>
> http://ayende.com/Blog/archive/2009/08/28/nhibernate-tips-amp-tricks-...
>
> Phil
>
> On Aug 24, 3:38 pm, George Mauer <[email protected]> wrote:
>
>
>
> > I have the following simple domain model representing a hierarchy:
>
> > public class FolderHierarchyNode
> > {
> > public virtual Guid Id { get; private set; }
> > public virtual string Name { get; private set; }
> > public virtual FolderHierarchyNode Parent { get; set; }
> > ICollection<FolderHierarchyNode> _children = new
> > HashSet<FolderHierarchyNode>();
> > public virtual IEnumerable<FolderHierarchyNode> Children { get
> > { return _children; } }
> > public FolderHierarchyNode() { }
> > }
>
> > I only need to track children, not the level in the hierarchy which I
> > should be able to do with this mapping:
>
> > <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
> > assembly="MyApp.Domain" namespace="MyApp.Domain.FolderHierarchy">
> > <class name="FolderHierarchyNode" table="NODES">
> > <id name="Id" column="PK_NODES" type="System.Guid" unsaved-
> > value="00000000-0000-0000-0000-000000000000">
> > <generator class="guid" />
> > </id>
> > <property name="Name" column="NDELNAME" />
>
> > <many-to-one name="Parent" column="FK_NODES"
> > class="FolderHierarchyNode" not-null="true" />
> > <set name="_children" access="field" cascade="all-delete-orphan"
> > lazy="false">
> > <key column="FK_NODES" />
> > <one-to-many class="FolderHierarchyNode"/>
> > </set>
> > </class>
> > </hibernate-mapping>
>
> > I can then query for the parent node simply like this:
> > public FolderHierarchyNode Get()
> > {
> > using (var s = _sessions.OpenSession())
> > return s.Linq<FolderHierarchyNode>()
> > .ToArray()
> > .Single(n => n.Parent.IsNull());
> > }
>
> > This generates at first the following SQL:
> > SELECT
> > this_.PK_NODES as PK1_4_0_, this_.NDELNAME as NDELNAME4_0_,
> > this_.FK_NODES as FK3_4_0_
> > FROM NODES this_
>
> > The results of this query should already contain all the information
> > necessary to build up the object tree but then I get a plethora more
> > select statements (I assume to fetch the children of each node):
>
> > SELECT children0_.FK_NODES as FK3_1_, children0_.PK_NODES as PK1_1_,
> > children0_.PK_NODES as PK1_4_0_, children0_.NDELNAME as NDELNAME4_0_,
> > children0_.FK_NODES as FK3_4_0_ FROM NODES children0_ WHERE
> > children0_.fk_nod...@p0;@p0 = 106e707a-699c-4c7e-a625-f3add43c0aee
> > SELECT children0_.FK_NODES as FK3_1_, children0_.PK_NODES as PK1_1_,
> > children0_.PK_NODES as PK1_4_0_, children0_.NDELNAME as NDELNAME4_0_,
> > children0_.FK_NODES as FK3_4_0_ FROM NODES children0_ WHERE
> > children0_.fk_nod...@p0;@p0 = 89e18057-eabe-466f-b3e6-e1ce02c90bfd
> > ....
> > etc.
>
> > What's the best way to get rid of these un-necessary sql calls? My
> > best guess is that I can drop the children from the mapping and in my
> > repository wire them up manually, but I'm hoping there's a more
> > integrated way to do this
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