I am trying a bunch of new (to me) feature of NHibernate and keep
running into problems. I am not sure whether this one is a bug or user
error, but when trying to eagerly fetch an entity with its collection
using the new Linq provider, I get what looks like a cartesian
product.
Parent entity -- "Operation":
public class Operation
{
public virtual Guid Id { get { return _id; } }
...
public virtual IList<OperationStep> Steps { get _steps; }
}
Child entity -- "OperationStep":
public abstract class OperationStep
{
public virtual Guid Id { get { return _id; } }
public virtual Operation Operation { get { return _operation; } }
...
}
public class InsertBatchStep : OperationStep
{
...
}
Linq query:
var operations = (from op in session.Query<Operation>
orderby op.DateCreated
select op).FetchMany(op =>
op.Steps).ToArray();
SQL:
select operation0_.Id as Id0_0_,
steps1_.Id as Id1_1_,
operation0_.DateCreated as DateCrea2_0_0_,
operation0_.Creator as Creator0_0_,
operation0_.Status as Status0_0_,
steps1_.OperationId as Operatio3_1_1_,
steps1_.StepOrder as StepOrder1_1_,
steps1_.ExecutionCount as Executio5_1_1_,
steps1_.DateOfNextExecution as DateOfNe6_1_1_,
steps1_.DateOfLastExecution as DateOfLa7_1_1_,
steps1_.Status as Status1_1_,
steps1_.LastError as LastError1_1_,
steps1_.Type as Type1_1_,
steps1_.OperationId as Operatio3_0__,
steps1_.Id as Id0__
from [Operation] operation0_
left outer join OperationStep steps1_
on operation0_.Id = steps1_.OperationId
order by operation0_.DateCreated asc
The Operation database table contains one operation, and the
OperationStep table contains four steps. The query returns 4
operations objects, each with 4 steps.
Mappings:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="FabricController" namespace="FabricController">
<class name="Operation" table="Operation">
<id name="Id">
<generator class="guid.comb" />
</id>
<property name="DateCreated"
access="nosetter.camelcase-underscore" /
>
<property name="Creator" access="nosetter.camelcase-underscore"
/>
<property name="Status" access="nosetter.camelcase-underscore"
/>
<bag name="Steps" table="OperationStep"
access="nosetter.camelcase-
underscore">
<key column="OperationId" />
<one-to-many class="OperationStep" />
</bag>
</class>
</hibernate-mapping>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="FabricController" namespace="FabricController">
<class name="OperationStep" table="OperationStep">
<id name="Id">
<generator class="guid.comb" />
</id>
<discriminator column="Type" />
<many-to-one name="Operation" column="OperationId"
access="nosetter.camelcase-underscore" />
<property name="StepOrder"
access="nosetter.camelcase-underscore" />
<property name="ExecutionCount" />
<property name="DateOfNextExecution" />
<property name="DateOfLastExecution" />
<property name="Status" />
<property name="LastError" />
<subclass name="OperationSteps.ConfirmBatchIndexedStep">
</subclass>
<subclass name="OperationSteps.InsertBatchStep">
</subclass>
<subclass name="OperationSteps.LoadBatchDataStep">
</subclass>
<subclass name="OperationSteps.PurgeDataStep">
</subclass>
</class>
</hibernate-mapping>
So is this me? What am I doing wrong?
Thanks in advance!
-Michael
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