DetachedCriteria: CreateCriteria vs CreateAlias

b3ardman · **Joined:** Tue Aug 15, 2006 11:01 am **Posts:** 10

NHibernate version:
1.2.0.4000
Mapping documents:
(abreviated for clarity)

Code:

<hibernate-mapping  auto-import="true" default-lazy="false" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="urn:nhibernate-mapping-2.2">
  <class name="FRS.Business.Job, FRS.Entities" table="JOBS">
    <id name="Id" access="property" column="JOBID" type="Int32" unsaved-value="0">
      <generator class="sequence">
        <param name="sequence">JOBSPK</param>
      </generator>
    </id>
    <bag name="Vehicles" access="field.camelcase-underscore" table="VEHICLES" lazy="false">
      <key column="JOBID" />
      <one-to-many class="FRS.Business.Vehicle, FRS.Entities" />
    </bag>
  </class>
  <class name="FRS.Business.Vehicle, FRS.Entities" table="VEHICLES">
    <id name="Id" access="property" column="VEHICLEID" type="Int32" unsaved-value="0">
      <generator class="native">
        <param name="sequence">VEHICLESPK</param>
      </generator>
    </id>
    <many-to-one name="Job" access="property" class="FRS.Business.Job, FRS.Entities" column="JOBID" />
    <bag name="RunningVehicles" access="field.camelcase-underscore" table="RUNNINGVEHICLES" lazy="false">
      <key column="VEHICLEID" />
      <one-to-many class="FRS.Business.RunningVehicle, FRS.Entities" not-found="ignore" />
    </bag>
    <joined-subclass name="FRS.Business.StandByVehicle, FRS.Entities" table="STANDBYS">
      <key column="VEHICLEID" />
    </joined-subclass>
  </class>
  <class name="FRS.Business.RunningVehicle, FRS.Entities" table="RUNNINGVEHICLES">
    <id name="Id" access="property" column="RUNNINGVEHICLEID" type="Int32" unsaved-value="0">
      <generator class="sequence">
        <param name="sequence">RUNNINGVEHICLESPK</param>
      </generator>
    </id>
    <many-to-one name="Vehicle" access="field.camelcase-underscore" class="FRS.Business.Vehicle, FRS.Entities" column="VEHICLEID" />
  </class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():

Code:

DetachedCriteria criteria = DetachedCriteria.For(typeof(Job), "j")
                    .CreateAlias(Job.Properties.Vehicles, "v", JoinType.LeftOuterJoin)
                    .CreateAlias("v." + Vehicle.Properties.RunningVehicles, "r", JoinType.LeftOuterJoin);
//go on to use the criteria as a subquery

Full stack trace of any exception that occurs:

Code:

NHibernate.QueryException: duplicate alias: j
at NHibernate.Loader.Criteria.CriteriaQueryTranslator.CreateAliasCriteriaMap()
at NHibernate.Loader.Criteria.CriteriaQueryTranslator..ctor(ISessionFactoryImplementor factory, CriteriaImpl criteria, Type rootEntityName, String rootSQLAlias)
at NHibernate.Loader.Criteria.CriteriaLoader..ctor(IOuterJoinLoadable persister, ISessionFactoryImplementor factory, CriteriaImpl rootCriteria, Type rootEntityName, IDictionary enabledFilters)
at NHibernate.Impl.SessionImpl.Find(CriteriaImpl criteria, IList results)
at NHibernate.Impl.SessionImpl.Find[T](CriteriaImpl criteria)
at NHibernate.Impl.CriteriaImpl.List[T]()

Name and version of the database you are using:
Oracle 10g

Diagnosis

This problem seems to be limited to DetachedCriteria.

If I try and do the same thing with session.CreateCriteria, it works fine.

Also, changing the CreateAlias to CreateCriteria works fine.

However, I can't do either of these as I need to left outer join on more than one child of the Job and this is part of a sub query.

Is this a limitation or a bug?

Thanks

b3ardman · **Joined:** Tue Aug 15, 2006 11:01 am **Posts:** 10

Related to this:

This produces a left outer join on the RunningVehicles.

Code:

DetachedCriteria criteria = DetachedCriteria.For ( typeof ( Job ), "j" );
criteria.CreateCriteria( "j." + Job.Properties.Vehicles, "v", JoinType.LeftOuterJoin);
criteria.CreateCriteria ( "v." + Vehicle.Properties.RunningVehicles, "r", JoinType.LeftOuterJoin );

This creates an inner join on RunningVehicles.

Code:

DetachedCriteria criteria = DetachedCriteria.For ( typeof ( Job ), "j" )
            .CreateCriteria( "j." + Job.Properties.Vehicles, "v", JoinType.LeftOuterJoin);
criteria.CreateCriteria ( "v." + Vehicle.Properties.RunningVehicles, "r", JoinType.LeftOuterJoin );

Again, correct behaviour or a bug?

mnichols · **Joined:** Mon Aug 21, 2006 9:18 am **Posts:** 179

HAve you looked at the GetCriteriaByAlias or GetCriteriaByPath methods of the DetachedCriteria object?
That would allow you to attach your criterion to different children.

Mike

b3ardman · **Joined:** Tue Aug 15, 2006 11:01 am **Posts:** 10

mnichols wrote:

HAve you looked at the GetCriteriaByAlias or GetCriteriaByPath methods of the DetachedCriteria object?
That would allow you to attach your criterion to different children.

Mike

AFAIK, they're only in the repository at the moment.