sql.py: add_row_num(): Add distinguishing comment to ADD COLUMN statement so that it will be cached. The distinguishing comment is required because sometimes column names are truncated, leading to unwanted collisions with previously-cached ADD COLUMN statements. It provides a way of distinguishing the full column name behind a particular ADD COLUMN statement.
sql.py: add_row_num(): Add distinguishing comment to ADD COLUMN statement so that it will be cached. The distinguishing comment is required because sometimes column names are truncated, leading to unwanted collisions with previously-cached ADD COLUMN statements. It provides a way of distinguishing the full column name behind a particular ADD COLUMN statement.