NH does not have code to clear a table, neither NH2 nor NH1.
Since NH2.1 *you* have an option to clear table/s representing a hierarchy
but nothing to clear a table representing a many-to-many table.

That said... somebody else have cleared your tables but you can continue
hoping in a bug somewhere else ;)

On Wed, May 4, 2011 at 4:36 PM, Mark Kharitonov
<[email protected]>wrote:

> Anyone?
>
> On 1 mai, 17:09, Mark Kharitonov <[email protected]> wrote:
> > Dear ladies and sirs.
> > I am not sure, if this is a bug, I am doing something wrong or this is
> > a bug in NH 2, but not NH 3 or later.
> > Anyway, we are using NH 2.
> >
> > I have two types of entities, here are the mappings:
> >
> >   <class name="Protocol, Entities" lazy="true" table="Protocol">
> >     <id name="Id" column="Id" type="string" >
> >       <generator class="assigned"/>
> >     </id>
> >
> >     <bag name="AssociatedEndpoints" table="Endpoint_Protocol"
> > access="noop">
> >       <key column="ProtocolId"/>
> >       <many-to-many column="EndpointId" class="Endpoint" />
> >     </bag>
> >   </class>
> >
> >   <class name="Endpoint, Entities" lazy="false" table="Endpoint">
> >     <id name="Id" column="Id" type="int" >
> >       <generator class="native"/>
> >     </id>
> >
> >     <bag name="SupportedProtocols" table="Endpoint_Protocol"
> > lazy="true">
> >       <key column="EndpointId"/>
> >       <many-to-many column="ProtocolId" class="Protocol" />
> >     </bag>
> >   </class>
> >
> > At some point, the database contains two endpoints and a dozen of
> > protocols - each endpoint is bound to each protocol. Meaning, the
> > Endpoint_Protocol table contains two rows per each protocol.
> >
> > Now, the server is restarted and one of the endpoints is refreshed. If
> > I throw away all irrelevant stuff (which has really nothing to do with
> > the problem), the relevant code is:
> >
> >       using (var session = GetSession())
> >       {
> >         var endpoint = FetchEndpoint(session, data.Id);
> >         using (var transaction = BeginTransaction(session))
> >         {
> >           transaction.Commit();
> >         }
> >       }
> >
> > Unless I do not understand something really basic, this code should
> > have no effect whatsoever on the database. And yet, after Commit
> > returns there the Endpoint_Protocol table is empty! Only the relations
> > were deleted, the entities themselves are fine.
> >
> > After debugging it, I have noticed this:
> > * Commiting flushes the entities and the collections found in the
> > session,
> > * While flushing the entities, it marks all those collections, which
> > are values of the mapped properties of some flushed entity - these are
> > the reachable collections.
> > * When flushing the collections, the unreachable ones are deleted from
> > the database.
> >
> > What happens, is that the fetch endpoint is reachable - of course. It
> > maps the SupportedProtocols property, hence all the protocol entities
> > are reachable as well. However, an AssociatedEndpoints collection
> > linked to each protocol entity is not reachable, because no mapped
> > property of Endpoint references it (recall thenoopaccess). At least,
> > this is how the  PocoEntityTuplizer extract the reachable values of an
> > entity - AssociatedEndpoints is not reachable according to it.
> >
> > Hence I witness these collections being deleted.
> >
> > Note, that once I remove the access="noop" making it the default
> > access and add the respective private property to the Protocol entity,
> > everything works just fine.
> >
> > What am I doing wrong?
> >
> > Thanks.
>
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-- 
Fabio Maulo

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