Generate UDT.getSupertype() and UDT.getSubtypes() #11371
Description
Dialects supporting UDTs could profit from a pre-generated type map of type Map<String, Class<?>>, which can be passed to JDBC to communicate all the mappings of UDTs for use with methods like CallableStatement.getObject(int, Map).
Currently, only Oracle would profit from this improvement as the PostgreSQL JDBC driver doesn't yet support the JDBC SQLData API (and we're parsing / serialising strings instead).
The improvement has 2 main benefits:
- The map doesn't have to be created every time for each serialisation / deserialisation of UDTs.
- It is a requirement for
TYPE .. UNDERtype hierarchies: Add support for Oracle TYPE .. UNDER type hierarchies #644
This issue takes care of code generation. The API is defined in #11372. A stub is implemented in CatalogImpl and SchemaImpl, returning empty maps.