Looks like none of the JDBC 4 drivers for PostgreSQL, MySQL and Derby
support SQLXML. MySQL got a little further than PostgreSQL, but it is
still not close.
So again we'll have to do a driver's job in Cayenne by mapping
java.sql.SQLXML to character columns (CLOB, TEXT, etc.). Feels sorta
meaningless, but I guess we can still go with such implementation for
Derby and PostgreSQL have a native XML DB type, but reading it in Java
requires special SQL syntax (XMLPARSE/XMLSERIALIZE) and doesn't seem
to provide any "optimizations" in XML access from Java. (i.e. it
converts internal XML representation to String that the Java code
would have to convert back to XML).
So that's where we stand on that...