[nhibernate-issues] [NHJIRA] Created: (NH-2650) HQL + theta-style join + Enumerable() + select only one entity = strange proxies' behaviour while iterating

[Kirill M. (JIRA) <nh...@gm...>]

HQL + theta-style join + Enumerable() + select only one entity = strange proxies' behaviour while iterating
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                 Key: NH-2650
                 URL: http://216.121.112.228/browse/NH-2650
             Project:  NHibernate
          Issue Type: Bug
          Components: DataProviders / Dialects
    Affects Versions: 3.1.0
            Reporter: Kirill Medvedev
            Priority: Major


I've created a test which consists of two classes:

Man:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Domain" namespace="Domain" default-lazy="true">
  <class name="Man" table="Men">
    <id name="Id" column="Id">
      <generator class="native"/>
    </id>
    <many-to-one name="Owner" class="Owner" column="OwnerId" cascade="save-update"/>
    <property name="Name"/>
  </class>
</hibernate-mapping>

Owner:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Domain" namespace="Domain" default-lazy="true">
  <class name="Owner" table="Owners">
    <id name="Id" column="Id">
      <generator class="native"/>
    </id>
    <property name="Name"/>
    <bag name="Men" cascade="save-update">
      <key column="OwnerID"/>
      <one-to-many class="Man"/>
    </bag>
  </class>
</hibernate-mapping>

If I write a simple hql-query without theta-joins, I get a lazily-loaded collection of proxies:

IEnumerable<Man> men = session.CreateQuery("from Man").Enumerable<Man>();

I can iterate through this collection without loading proxies:
foreach (Man each in men) 
{
   //No code here, only iterating... Proxies are not loaded here, as expected.
}

But when I add theta-style join to this query...
IEnumerable<Man> result = session.CreateQuery("select m from Man m left join m.Owner").Enumerable<Man>();

NHibernate generates acceptable TSQL and builds SafetyEnumerable collection

select man0_.Id as col_0_0_
from   Men man0_
       left outer join Owners owner1_
         on man0_.OwnerId = owner1_.Id

but (!) when I add iterating logic without accessing to any properties
foreach (Man each in men) 
{
    //No code here! Only iterating through elements
}

new queries go to database each iteration, and load each entity:

SELECT man0_.Id      as Id1_0_,
       man0_.OwnerId as OwnerId1_0_,
       man0_.Name    as Name1_0_
FROM   Men man0_
WHERE  man0_.Id = 5098 /* @p0 */


Therefore I can't even convert this IEnumerable<Man> to List<Man> without loading the whole list of objects, because List constructor iterates through IEnumerable collection to add this collection to itself

//public List(IEnumerable<T> collection) - constructor
while (enumerator.MoveNext())
{
   this.Add(enumerator.Current);
}

Question: Is this behaviour designed to behave such way intentionally? It's strange that different hql queries return SafetyEnumerable collection which behaves differently while iterating through it (in case of non-theta joined queries, collection's entities are not loaded while iterating through it (without accessing any properties), but in theta-joined queries, entities are loaded while iterating through collection). Strange proxies' behaviour.

Thank you.

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