convert query result to dim result

This modifies the zone list command in such a way, that a query result
could be directly returned to the response.

With a bit of work, large query results could be rendered with a
streaming json renderer to the output.

zone_list.go

@@ -32,17 +32,18 @@ func zoneList(c *Context, req Request, res *Response) error {
 		return nil
 	}
 
-	selClause := query.FieldListToSelect(options.Attributes, zoneListMap)
-
-	rows, err := c.tx.Query(fmt.Sprintf(`select %s from zones z`, selClause))
+	selClause := query.FieldListToSelect("z", options.Attributes, zoneListMap)
+	from := "zones z"
+	queryStr := fmt.Sprintf(`select %s from %s`, selClause, from)
+	rows, err := c.tx.Query(queryStr)
 	if err != nil {
 		res.AddMessage(LevelError, "could not return result")
-		return fmt.Errorf("could not get zone list: %s", err)
+		return fmt.Errorf("could not get zone list: %s - query: %s", err, queryStr)
 	}
 	defer rows.Close()
-	res.Result["zones"], err = query.RowsToMap(rows)
+	res.Result, err = query.RowsToMap(rows)
 	if err != nil {
-		delete(res.Result, "zones")
+		res.Result = nil
 		res.AddMessage(LevelError, "could not return result")
 		return fmt.Errorf("could not parse zone list: %v", err)
 	}