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  1. PO
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    <p>NH sometimes requires to set references to null. Usually this is to avoid problems in models where circular references exist. But it is not always clever enough to find a way to avoid it, even if the is one.</p> <p>So it may require to allow nulls in some foreign key fields, of course not only in the mapping file, also in the database. It actually <em>should</em> solve the problem.</p> <hr> <p><strong>Alternatively</strong>, you could also delete the data table by table using HQL. This works fine in all cases where you don't have inheritance and if you know all entities and the order to delete them:</p> <pre><code>object entityId; // gets keys to delete List&lt;object&gt; keyIds = Session .CreateQuery("select id from Key where Entity = :entity") .SetEntity("entity", Entity) .List&lt;object&gt;(); // delete KeyAttribute which reference the key Session.CreateQuery("delete KeyAttribute where Key.id in (:keyIds)") .SetParameterList("keyIds", keyIds) .ExecuteUpdate(); // delete the keys Session.CreateQuery("delete Key where id in (:keyIds)") .SetParameterList("keyIds", keyIds) .ExecuteUpdate(); // get attributes to delete List&lt;object&gt; attributeIds = Session .CreateQuery("select id from Attribute where Entity = :entity") .SetEntity("entity", Entity) .List&lt;object&gt;(); // delete KeyAttributes which reference the attributes Session.CreateQuery("delete KeyAttribute where Attribute.id in (:attributeIds)") .SetParameterList("attributeIds", attributeIds ) .ExecuteUpdate(); // delete the attributes Session.CreateQuery("delete Attribute where id in (:attributeIds)") .SetParameterList("attributeIds", attributeIds ) .ExecuteUpdate(); Session.CreateQuery("delete Entity where id = :entityId") .SetParameter("entityId", Entity.Id) .ExecuteUpdate(); </code></pre> <p>Note:</p> <ul> <li>You may break the parameter lists into piece if they exceed the size of around 2000 (in SQL Server).</li> <li>The session gets out of synch when deleting directly in the database. This doesn't cause any problems when deleting is all you do. When you are doing other staff in the same session, clear the session after deleting.</li> </ul>
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    1. PONHibernate exception while deleting object graph: not-null property references a null or transient value
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    1. USStefan Steinegger
    1. USStefan Steinegger
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    1. COThank you for the answer. I think that's pretty hard coding, especially in HQL! Now I'm trying to override CascadeBeforeDelete in own DeleteEventListener, I think I can set the right deletion order by that way
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      1. USEvgeniyK
    2. CO@EvgeniyK: wait a minute, I said that allowing nulls *should* solve the problem. The "hard coded" part is just giving you more control and may be a good performance optimization.
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      1. USStefan Steinegger
    3. COYeap, If I drop all constrains in NH & MS SQL, of course everything would be alright, no question; In Russia it called: "unsportsmanlike behavior" =))
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