Use catalog views for table metadata.

Sqoop currently uses JDBC interface javax.sql.DatabaseMetaData for retrieving table metadata for things such as identifying the primary key column. This is error prone, not uniformly supported by all vendors and drivers, and usually has lower performance than direct queries. Furthermore, due to inconsistent semantics of users, schemas and privileges across different vendors, this interface is not sufficiently reliable for consistent results.

It would therefore be preferable for Sqoop to use catalog views for obtaining table metadata where possible.