Orpheus DDL Helper

Orpheus is database engine type agnostic. This means that it does not include any code targeting a specific database engine.

Despite the fact, that SQL based database engines use the SQL language, there are differences between them.

Here is where the IOrpheusDDLHelper comes into play.

Every IOrpheusDatabase requires a IOrpheusDDLHelper. Orpheus provides out of the box, helpers for SQL Server, MySQL, and PostgreSQL database engines (OrpheusSQLServerDDLHelper, OrpheusMySQLDDLHelper, OrpheusPostgreSQLDDLHelper).

So what do these helpers do?

As mentioned above, they reconcile differences between the different database engines.

For example SQL Server natively supports the UID type while MySQL does not. The helper will give this kind of information to the IOrpheusDatabase.

They're also where batched multi-row INSERT/UPDATE/DELETE commands get built, and — for tables with a DB-generated key — where the engine-specific technique for retrieving generated keys from a multi-row insert lives (SQL Server uses MERGE+OUTPUT with a correlation column, PostgreSQL uses INSERT...RETURNING, MySQL derives the range from LAST_INSERT_ID()), since there's no ADO.NET-portable way to do this generically.

You can implement your own IOrpheusDDLHelper and register it in OrpheusORM.

Implementing a custom IOrpheusDDLHelper

Implementing your own DDLHelper is not a requirement.

However if Orpheus does not provide one for you, for your database engine, it's quite easy to implement your own.

All you have to do is to create a class that implements IOrpheusDDLHelper,implement your logic and register it in Orpheus. Here is how you can register a custom DDL helper.