code: public String generateSelectAllExistingFieldsSql(Connection connection, String namespace) throws SQLException {
          // select all columns from table
          // FIXME This is postgres-specific and needs to be made generic for non-postgres databases.
          PreparedStatement statement = connection.prepareStatement(
              "SELECT column_name FROM information_schema.columns WHERE table_schema = ? AND table_name = ?"
          );
          statement.setString(1, namespace);
          statement.setString(2, name);
          ResultSet result = statement.executeQuery();
  
          // get result and add fields that are defined in this table
          List<Field> existingFields = new ArrayList<>();
          while (result.next()) {
              String columnName = result.getString(1);
              existingFields.add(getFieldForName(columnName));
          }
  
          String tableName = String.join(".", namespace, name);
          String fieldPrefix = tableName + ".";
          return String.format(
              "select %s from %s", commaSeparatedNames(existingFields, fieldPrefix, true), tableName
          );
      }
docs: Generate a select statement from the columns that actually exist in the database table.  This method is intended
  to be used when exporting to a GTFS and eventually generates the select all with each individual field and
  applicable transformations listed out.