[This is preliminary documentation and subject to change.]
This is the PrimaryKeys method of the MsiDatabase object. This method returns an MsiRecord object containing the table name in field 0 and the column names (comprising the primary keys) in succeeding fields corresponding to their column numbers. The field count of the record is the count of primary key columns.
object.PrimaryKeys(table)
The PrimaryKeys method cannot be used with the _Tables table or the _Columns table.