R – NHibernate – How to change schemas during run time

dynamicnhibernateschema

I'm using NHibernate to connect to an ERP database on our DB2 server. We have a test schema and a production schema. Both schemas have the same table structure underneath. For testing, I would like to use the same mapping classes but point NHibernate to the test environment when needed and then back when in production. Please keep in mind that we have many production schemas and each production schema has an equivalent test schema.

I know that my XML mapping file has a schema property inside it, but since it's in XML, it's not like I can change it via a compiler directive or change the schema property based on a config file.

Any ideas?

Thank You.

Best Answer

No need to specify schema in the mappings: there's a SessionFactory-level setting called default_schema. However, you can't change it at runtime, as NHibernate pregenerates and/or caches SQL queries, including the schema part.

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R – How to update database table schemas with NHibernate schema generation

The SchemaUpdate object provides database schema updating, by apparently generating and executing a series of SQL UPDATE statements (as well as constraint statements) when it's void Execute(bool script, bool doUpdate) function is called. The SchemaUpdate class is in the NHibernate.Tool.hbm2ddl namespace, which can be found in the Nhibernate.dll file.

SchemaUpdate is mentioned in chapter 15 of the nhibernate 1.0.2 toolset guide, here (section 15.1.5).

"The NHibernate FAQ" had (link now expired) a more complete example of how to use SchemaUpdate:

[Test]
public void Update_an_existing_database_schema()
{
    _cfg = new Configuration();
    _cfg.Configure();
    _cfg.AddAssembly(Assembly.LoadFrom("DataLayer.dll"));
    var update = new SchemaUpdate(_cfg);
    update.Execute(true, false);
}

.net – NHibernate – How to map to a class that has no table (for custom sql queries)

What you're looking for are projections. First of all you need to modify your query

  <sql-query name="usp_SomeCustomSproc">
    <return-scalar column="Id" type="Int32"/>
    <return-scalar column="Name" type="String"/>

    exec usp_SomeCustomSproc :TrackedEntityID

  </sql-query>

Then in the code where you call it you specify a result transformer. The AliasToBeanTransformer will take column aliases and map them to properties on the object.

session.GetNamedQuery("usp_SomeCustomSproc")
       .SetInt32("TrackedEntityID", 15)
       .SetResultTransformer(Transformers.AliasToBean<CustomObject>())
       .List<CustomObject>()

Best Answer

Related Solutions

R – How to update database table schemas with NHibernate schema generation

.net – NHibernate – How to map to a class that has no table (for custom sql queries)

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