how to optimize mysql group by - mysql

Question

table:
CREATE TABLE IF NOT EXISTS `l_not_200_page` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`server` tinyint(3) unsigned NOT NULL,
`domain` tinyint(3) unsigned NOT NULL,
`page` varchar(128) NOT NULL,
`query_string` varchar(384) NOT NULL,
`status` smallint(5) unsigned NOT NULL,
PRIMARY KEY (`id`),
KEY `idx_time_domain_status_page` (`time`,`domain`,`status`,`page`),
KEY `page` (`page`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
explain:
EXPLAIN SELECT *
FROM `l_not_200_page`
WHERE TIME
BETWEEN TIMESTAMP( '2014-03-25' )
AND TIMESTAMP( '2014-03-25 23:59:59' )
AND domain =1
AND STATUS = 404
GROUP BY PAGE
1
SIMPLE
l_not_200_page
range
idx_time_domain_status_page
idx_time_domain_status_page
7
NULL
1
Using where; Using temporary; Using filesort
it's very slow, how to optimize ?
sql:
SELECT PAGE , COUNT( * ) AS cnt
FROM l_not_200_page
WHERE TIME
BETWEEN TIMESTAMP( '2014-03-26 12:00:00' )
AND TIMESTAMP( '2014-03-26 12:30:00' )
AND domain =1
AND STATUS = 499
GROUP BY PAGE ORDER BY cnt DESC
LIMIT 100
the daily amount of data about 900w

Answer 1

Change the index to:
create index `idx_domain_status_time_page` on l_not_200_page(`domain`, `status`, `time`, `page`)
When MySQL uses an index for a where clause, the best index has all the fields in equality comparisons followed by one with an inequality, such as between. With time as the first element, it doesn't use the index for domain and status (well, it uses an index scan instead of a direct lookup).
For further optimization, you can get rid of the group by by choosing one row per page:
SELECT lp.* FROM l_not_200_page lp WHERE TIME BETWEEN TIMESTAMP( '2014-03-25' ) AND TIMESTAMP( '2014-03-25 23:59:59' ) AND
domain = 1 AND STATUS = 404 AND
NOT EXISTS (select 1
from l_not_200_page lp2
where lp2.page = lp.page and
lp2.domain = 1 and lp2.status = 404 and
lp2.TIME BETWEEN TIMESTAMP('2014-03-25) AND TIMESTAMP('2014-03-25 23:59:59') AND
lp2.id > lp.id
)
For this, an additional index on (page, domain, status, time) would help.