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 the noop access). 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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