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

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

     [ http://216.121.112.228/browse/NH-2650?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Fabio Maulo updated NH-2650:
----------------------------

    Component/s:     (was: DataProviders / Dialects)
                 Core

> HQL + theta-style join + Enumerable() + select only one entity = strange proxies' behaviour while iterating
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: NH-2650
>                 URL: http://216.121.112.228/browse/NH-2650
>             Project:  NHibernate
>          Issue Type: Bug
>          Components: Core
>    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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