User defined types

 The MonetDB kernel supports creation of user defined types, e.g. geometric types. The relationship between SQL and MAL world is expressed using an external name.

CREATE TYPE type_name EXTERNAL NAME type_identification

DROP TYPE type_name [RESTRICT | CASCADE]

The implementation of new atomary types is best postponed until there is no other performance-wise acceptable solution. Addition of an atomary type in the kernel would be beneficial if it is also complemented with bulk-operations and when type specific optimizers could exploit there semantics.