Hmmm... you may have to push this into a build step that generates your mapping
files. So your formula would look something like this:
<property name="MetaTrainName" formula="(SELECT SomeField FROM
${Qualify('MyTableName')})"/>
Then you could have an NAnt target that would set up brail or some other
templating language, process the mapping files, and copy them to a known
directory.
Does that make sense?
-tyler
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Stefan Nobis
Sent: Tuesday, June 23, 2009 1:38 AM
To: [email protected]
Subject: [nhusers] Denormalized Domain Model
Hi.
My database schema has quite some references and in order to avoid loading
always a great part of the wohle object graph I would like to get some of the
often used detail data directly in the entity without denormalizing the schema.
Two concrete examples: In the following mappings the class 'Waggongroup' should
be extended with the name of the associated MetaTrain
(Waggongroup.Schedule.MetaTrain.Name). The other detail I'm interested in is
the StartingStation of the first associated NetworkSection in the Routing list
of the Waggongroup and the Destination of the last associated NetworkSection in
the Routing list.
Here is the mapping:
-----<Mappings>---------------------------------------------
<class name="Waggongroup">
<id .../>
<version .../>
<many-to-one name="Schedule" class="Schedule" not-null="true"/>
<list name="Routing">
<key .../>
<index column="route_order"/>
<many-to-many class="NetworkSection"/>
</list>
...
</class>
<class name="Schedule">
<id .../>
<version .../>
<many-to-one name="MetaTrain" class="MetaTrain" not-null="true"/>
...
</class>
<class name="MetaTrain">
<id .../>
<version .../>
<property name="Name" type="String" not-null="true" unique="true"/>
...
</class>
<class name="NetworkSection">
<id .../>
<version .../>
<many-to-one name="StartingStation" class="Location" not-null="true"
unique-key="UQ_Track"/>
<many-to-one name="Destination" class="Location" not-null="true"
unique-key="UQ_Track"/>
...
</class>
<class name="Location">
<id .../>
<version .../>
<property name="Name" type="String" not-null="true"/>
<property name="Mnemonic" type="String" not-null="true" unique="true"/>
...
</class>
-----</Mappings>--------------------------------------------
My first attempt to solve at least the easier of the two denomalizations is to
use a property with a formula, something like the following in the Waggongroup:
<property name="MetaTrainName" formula="(SELECT ....)"/>
This kind of works. The problem is that I need to support SqLite (for testing
purposes), MS SQL Server, and Oracle. All users of Oracle have a default schema
that is different than the schema where the tables live so all objects have to
be fully qualified with the schema name. On the other hand MS-SQL and SqLite
don't have this problem and both don't use schemas. Is there any way to use
formula in such a way that would work with both cases? Or even better: Would it
be possible to use HQL for the formula (or is such a support planned for the
(near) future)?
Has anybody other ideas how to achive the denormalization in the domain model
without denormalizing the database?
--
Until the next mail...,
Stefan.
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