[sr-dev] db version of nat pinger

[Juha Heinanen]

Klaus Darilion writes:

> Not sure if an index would be much faster here. Also the cflags & 0 = 0 
> should be rather fast.

klaus,

as i wrote, if an operation is done on index field, the index cannot be
used:

mysql> explain select SQL_NO_CACHE received, contact, socket, cflags, path, ruid from location where cflags & 16 = 16 and id % 20 = 0;
+----+-------------+----------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table    | type | possible_keys | key  | key_len | ref  | rows  | Extra       |
+----+-------------+----------+------+---------------+------+---------+------+-------+-------------+
|  1 | SIMPLE      | location | ALL  | NULL          | NULL | NULL    | NULL | 10035 | Using where |
+----+-------------+----------+------+---------------+------+---------+------+-------+-------------+

mysql> explain select SQL_NO_CACHE received, contact, socket, cflags, path, ruid from location where cflags >= 15 and id % 20 = 0;
+----+-------------+----------+-------+---------------+------------+---------+------+------+-------------+
| id | select_type | table    | type  | possible_keys | key        | key_len | ref  | rows | Extra       |
+----+-------------+----------+-------+---------------+------------+---------+------+------+-------------+
|  1 | SIMPLE      | location | range | cflags_idx    | cflags_idx | 4       | NULL | 1309 | Using where |
+----+-------------+----------+-------+---------------+------------+---------+------+------+-------------+

in terms of execution time, the latter is about half of previous.

-- juha