[nhibernate-issues] [JIRA] Updated: (NH-826) Using Criteria to query for an item throws on Flush in some situations

[NHibernate J. <mik...@us...>]

     [ http://jira.nhibernate.org/browse/NH-826?page=all ]

Aaron Jensen updated NH-826:
----------------------------

    Attachment: NH826.patch

This patch fixes it for me.  It's hacky and doesn't feel right, so I'm sure theres a more top down approach to this.  Here's my side of a conversation I had with Ayende explaining the issue:
(1:30:11 PM) Aaron: it's hacky
(1:30:25 PM) Aaron: and i dont know if its the right solution
(1:31:05 PM) Aaron: the issue is that the loadelementsfromcolleciton gets the collectionpersisters for all possible collections for an entity (including it's subclasses)
(1:31:38 PM) Aaron: so if an entity is of the base class, it creates a collection that belongs to the subclass
(1:31:46 PM) Aaron: and it's automatically unreferenced
(1:31:49 PM) Aaron: because it can't be referenced
(1:32:13 PM) Aaron: ok, let me back up... you have a subclass
(1:32:19 PM) Aaron: and you have a base class
(1:32:26 PM) Aaron: sub has a collection
(1:32:29 PM) Aaron: base does not
(1:32:36 PM) Aaron: then you have a container class, that has a collection of base
(1:32:48 PM) Aaron: you get a row from the resultset
(1:32:56 PM) Aaron: and you've got to hydrate all the collections it contains
(1:33:18 PM) Aaron: so, if you get container fetch base fetch collection
(1:33:30 PM) Aaron: or just container join base fetch collection
(1:34:12 PM) Aaron: so the collection persister for the collection is there, and it's owner is base
(1:34:30 PM) Aaron: even though base does not have that collection
(1:34:53 PM) Aaron: at some point the entity's type is determined.. and it's instantiated
(1:34:59 PM) Aaron: so base is instantiated
(1:35:04 PM) Aaron: because that's what it is, it's NOT sub
(1:35:34 PM) Aaron: but the collectionpersister for the collection still exists because it doesn't know at the time it's created that it's not needed... AND it's needed later if there is a sub in the container
(1:35:55 PM) Aaron: so either the set of collectionpersisters needs to change on each row based on the type
(1:36:08 PM) Aaron: or we need to filter using reflection like my patch does
(1:37:31 PM) Aaron: no idea how it worked in 1.0
(1:37:34 PM) Aaron: didn't look at the code
(1:37:41 PM) Aaron: it may not have
(1:37:49 PM) Aaron: because they changed it to fetch as default
(1:37:55 PM) Aaron: so we may have never seen it

> Using Criteria to query for an item throws on Flush in some situations
> ----------------------------------------------------------------------
>
>          Key: NH-826
>          URL: http://jira.nhibernate.org/browse/NH-826
>      Project: NHibernate
>         Type: Bug
>   Components: Core
>     Versions: 1.2.0.Beta2
>     Reporter: Aaron Jensen
>      Fix For: 1.2.0.Beta3
>  Attachments: NH826.patch, NHibernateTest.zip
>
> The situation is best described by the attached sample project, but I will attempt to explain in words when this problem occurs.
> EntityA has a many-to-many to EntityB
> EntityB has a subclass EntityC
> EntityC has a one-to-many to EntityD
> If you create an EntityB and associate it to EntityA, then query for EntityA via Criteria (but not via HQL) then Session.Flush() will fail with: 
> NHibernate.HibernateException: You may not dereference an collection with cascade="all-delete-orphan"
>    at NHibernate.Impl.SessionImpl.UpdateUnreachableCollection(IPersistentCollection coll) in c:\net\nhibernate\nhibernat
> e\src\NHibernate\Impl\SessionImpl.cs:line 3957
>    at NHibernate.Impl.SessionImpl.FlushCollections() in c:\net\nhibernate\nhibernate\src\NHibernate\Impl\SessionImpl.cs:
> line 3802
>    at NHibernate.Impl.SessionImpl.FlushEverything() in c:\net\nhibernate\nhibernate\src\NHibernate\Impl\SessionImpl.cs:l
> ine 3090 
> The collection it is complaining about is a collection of EntityD objects which should never have been created in the first place.

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