change_column_required (KirbyBase::KBTable)

    # File lib/kirbybase.rb, line 2733
        def change_column_required(col_name, required)
            raise "Do not execute this method in client/server mode!" if \
             @db.client?

            raise ":recno is always required!" if col_name == :recno

            raise 'Invalid column name: ' % col_name unless \
             @field_names.include?(col_name)

            raise 'Required must be either true or false!' unless \
             [true, false].include?(required)

            @db.engine.change_column_required(self, col_name, required)

            # Need to reinitialize the table instance and associated indexes.

            @db.engine.remove_recno_index(@name)
            @db.engine.remove_indexes(@name)

            update_header_vars
            create_indexes
            create_table_class unless @db.server?
        end