如何获取所有实体-Nhibernate选择具有多级深度的n + 1

Question

To explain my question let's assume I've got these two classes:

public class Grandfather
{
     private int Id;
     private int Version;
     private IList<Father> Childrens; 
}

public class Father
{
    private int Id;
    private int Version;
    private IList<double> ChildrensAges;
    private IList<double> ChildrenGradesOnMath;
    private IList<int> ChildrenNumberOfFriends;
}

The Mapping files are:

for Grandfather:

 <?xml version="1.0" encoding="utf-8" ?>
    <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
     namespace="Entities" assembly="Entities">
     <class name="Grandfather" table="Grandfather">
     <id name="Id" column="Id" type="Int32" unsaved-value="0">
         <generator class="assigned" />
        </id>
         <version name="Version" column="Version" type="Int32" unsaved-value="0" access="property"/>
         <bag name="Childrens" table="Childrens" cascade="all-delete-orphan" fetch="join" lazy="false">
            <key column="GrandfatherOwnerId"/>
            <one-to-many class="Father"
       </bag>
    </class>
    </hibernate-mapping>

for Father:

    <?xml version="1.0" encoding="utf-8" ?>
    <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
     namespace="Entities" assembly="Entities">
     <class name="Father" table="Father">
     <id name="Id" column="Id" type="Int32" unsaved-value="0">
         <generator class="assigned" />
     </id>
     <version name="Version" column="Version" type="Int32" unsaved-value="0" access="property"/>
     <list name="ChildrensAges" table="ChildrensAges" fetch="join" lazy="false">
        <key column="ChildrensAgesDBId"/>
        <index column="Ordinal"/>
        <element column="Value" type="System.Double"/>
    </list>
    <list name="ChildrenGradesOnMath" table="ChildrenGradesOnMath" fetch="join" lazy="false">
        <key column="ChildrenGradesOnMathDBId"/>
        <index column="Ordinal"/>
        <element column="Value" type="System.Double"/>
    </list>
    <list name="ChildrenNumberOfFriends" table="ChildrenNumberOfFriends" fetch="join" lazy="false">
        <key column="ChildrenNumberOfFriendsDBId"/>
        <index column="Ordinal"/>
        <element column="Value" type="System.Int"/>
    </list>
</class>
</hibernate-mapping>

I want to fetch all Grandfathers from the DB. When I use the query (on DB with 10,000 grandfathers, each grandfather has one child):

IList queryEntities = session.CreateQuery("from Grandfather").List();

It generate 10,000*5 queries and it take too much time.

What is the best way to fetch all the data (I need it all so it have to be eager) in one query?

Thanks in advanced :-)

Answer 1

Use FetchMany

something like the following

var grandfathers = (from grin session.Query<Grandfather>()
            select gr)
            .FetchMany(f => f.Childrens)
            .ThenFetch(fc = > fc.ChildrensAges)
            .ToList();

and you might extend this to ThenFetch or ThenFetchMany to get items on Father.