list_tabledata_callback calls the supplied callback with each page
of data.
list_tabledata_iter returns a named list with functions next_
(fetches one chunk of rows), next_paged (fetches arbitrarily many
rows using a specified page size), is_complete (checks if all rows
have been fetched), get_schema (returns the schema of the table),
and get_rows_fetched (returns the number of rows already fetched).