Manage schema evolution for an application.
generation
(Attribute)
Current schema generation
minimum_generation
(Attribute)
Minimum supported schema generation
* = required
evolve(context, generation)
Evolve a database to the given schema generation.
The database should be assumed to be at the schema generation one less than the given generation argument. In other words, the evolve method is only required to make one evolutionary step.
The context argument has a connection attribute, providing a database connection to be used to change the database. A context argument is passed rather than a connection to make it possible to provide additional information later, if it becomes necessary.
This method should not commit a transaction. The transaction will be committed by the caller if there is no error. It is acceptable to commit a transaction if there are no subsequent operations. The method may create savepoints.
getInfo(generation)
Return an information string about the evolution that is used to upgrade to the specified generation.
If no information is available, None should be returned.