sql_io.py: Added row_num_col_def for use by import_csv(). The row_num column will be necessary again because PostgreSQL unfortunately does not return rows in inserted order (or any stable order: "If sorting is not chosen, the rows will be returned in an unspecified order [which] must not be relied on" <http://www.postgresql.org/docs/8.3/static/queries-order.html>), so an explicit ORDER BY is always needed to ensure staging table rows are retrievable in the order they were inserted.
sql_io.py: Added row_num_col_def for use by import_csv(). The row_num column will be necessary again because PostgreSQL unfortunately does not return rows in inserted order (or any stable order: "If sorting is not chosen, the rows will be returned in an unspecified order [which] must not be relied on" <http://www.postgresql.org/docs/8.3/static/queries-order.html>), so an explicit ORDER BY is always needed to ensure staging table rows are retrievable in the order they were inserted.