Question

I have a table with 18,310,298 records right now.

And next query

SELECT COUNT(obj_id) AS cnt
FROM
`common`.`logs`
WHERE 
`event` = '11' AND
`obj_type` = '2' AND
`region` = 'us' AND 
DATE(`date`) = DATE('20120213010502');

With next structure

CREATE TABLE `logs` (
  `log_id` int(11) NOT NULL AUTO_INCREMENT,
  `event` tinyint(4) NOT NULL,
  `obj_type` tinyint(1) NOT NULL DEFAULT '0',
  `obj_id` int(11) unsigned NOT NULL DEFAULT '0',
  `region` varchar(3) NOT NULL DEFAULT '',
  `date` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`log_id`),
  KEY `event` (`event`),
  KEY `obj_type` (`obj_type`),
  KEY `region` (`region`),
  KEY `for_stat` (`event`,`obj_type`,`obj_id`,`region`,`date`)
) ENGINE=InnoDB AUTO_INCREMENT=83126347 DEFAULT CHARSET=utf8 COMMENT='Logs table' |

and MySQL explain show the next

+----+-------------+-------+------+--------------------------------+----------+---------+-------------+--------+----------+--------------------------+
| id | select_type | table | type | possible_keys                  | key      | key_len | ref         | rows   | filtered | Extra                    |
+----+-------------+-------+------+--------------------------------+----------+---------+-------------+--------+----------+--------------------------+
|  1 | SIMPLE      | logs  | ref  | event,obj_type,region,for_stat | for_stat | 2       | const,const | 837216 |   100.00 | Using where; Using index |
+----+-------------+-------+------+--------------------------------+----------+---------+-------------+--------+----------+--------------------------+
1 row in set, 1 warning (0.00 sec)

Running such query in daily peak usage time take about 5 seconds.

What can I do to make it faster ?

UPDATED: Regarding all comments I modified INDEX and take off DATE function in WHERE clause

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| logs  |          0 | PRIMARY  |            1 | log_id      | A         |    15379109 |     NULL | NULL   |      | BTREE      |         |
| logs  |          1 | event    |            1 | event       | A         |          14 |     NULL | NULL   |      | BTREE      |         |
| logs  |          1 | obj_type |            1 | obj_type    | A         |          14 |     NULL | NULL   |      | BTREE      |         |
| logs  |          1 | region   |            1 | region      | A         |          14 |     NULL | NULL   |      | BTREE      |         |
| logs  |          1 | for_stat |            1 | event       | A         |         157 |     NULL | NULL   |      | BTREE      |         |
| logs  |          1 | for_stat |            2 | obj_type    | A         |         157 |     NULL | NULL   |      | BTREE      |         |
| logs  |          1 | for_stat |            3 | region      | A         |         157 |     NULL | NULL   |      | BTREE      |         |
| logs  |          1 | for_stat |            4 | date        | A         |         157 |     NULL | NULL   |      | BTREE      |         |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+


    mysql> explain extended SELECT COUNT(obj_id) as cnt 
    ->     FROM `common`.`logs` 
    ->     WHERE `event`= '11' AND 
    ->     `obj_type` = '2' AND 
    ->     `region`= 'est' AND 
    ->     date between '2012-11-25 00:00:00' and '2012-11-25 23:59:59';
+----+-------------+-------+-------+--------------------------------+----------+---------+------+------+----------+-------------+
| id | select_type | table | type  | possible_keys                  | key      | key_len | ref  | rows | filtered | Extra       |
+----+-------------+-------+-------+--------------------------------+----------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | logs  | range | event,obj_type,region,for_stat | for_stat | 21      | NULL | 9674 |    75.01 | Using where |
+----+-------------+-------+-------+--------------------------------+----------+---------+------+------+----------+-------------+

It seems it’s running faster. Thanks everyone.

Answer 1

@Joni already explained what is wrong with your index. For query, I assume that your example query selects all records for 2012-02-13 regardless of time. You can change the where clause to use >= and < instead of DATE cast:

SELECT COUNT(obj_id) AS cnt
FROM
`common`.`logs`
WHERE 
`event` = 11 AND
`obj_type` = 2 AND
`region` = 'us' AND 
`date` >= DATE('20120213010502') AND
`date` <  DATE('20120213010502') + INTERVAL 1 DAY