speed up this query ( join + mediumtext field) - mysql

Question

I have this query
SELECT
t.name,t.userid,t.date,t.cat_id,t.forum_id,t.reply,t.hidden,t.moderated,t.sticky,t.statut,t.poll,t.helpful,t.del,
t_data.message,
user.name AS author_name,user.level AS author_level,user.is_globalMod AS author_global,user.award,<br>
user.statut AS author_statut,user.posts AS user_posts,user.point AS user_points,user.title AS user_title,
user.image AS user_avatar,user.sex AS user_sex,user.other_level,user.hid_posts
FROM frm_thread AS t
LEFT JOIN frm_thread_data AS t_data ON t_data.thread_id = t.id
LEFT JOIN frm_member AS user ON user.id =t.userid
WHERE t.id = 248925
frm_thread is
CREATE TABLE IF NOT EXISTS `frm_thread` (
`id` mediumint(7) unsigned NOT NULL auto_increment,
`last_userid` int(10) unsigned NOT NULL,
`last_date` int(10) unsigned default NULL,
`forum_id` tinyint(5) unsigned NOT NULL,
`cat_id` tinyint(3) unsigned NOT NULL,
`name` varchar(250) collate utf8_unicode_ci NOT NULL,
`userid` int(10) unsigned NOT NULL,
`date` int(10) unsigned default NULL,
`view` mediumint(5) unsigned NOT NULL,
`reply` smallint(4) NOT NULL,
`sticky` tinyint(1) unsigned NOT NULL,
`linked` tinyint(1) unsigned NOT NULL,
`linked_order` tinyint(2) unsigned NOT NULL,
`spam` tinyint(1) unsigned NOT NULL,
`statut` tinyint(1) unsigned NOT NULL,
`moderated` tinyint(1) unsigned NOT NULL,
`hidden` tinyint(1) unsigned NOT NULL,
`poll` smallint(5) unsigned NOT NULL,
`del` tinyint(1) unsigned NOT NULL,
`t_icon` smallint(10) unsigned NOT NULL,
`helpful` int(10) unsigned NOT NULL
PRIMARY KEY (`id`),
KEY `forum_id` (`forum_id`),
KEY `last_date` (`last_date`,`date`,`sticky`),
KEY `linked` (`linked`),
KEY `date` (`date`),
KEY `userid` (`userid`),
KEY `last_userid` (`last_userid`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=249014 ;
frm_thread_data
CREATE TABLE IF NOT EXISTS `frm_thread_data` (
`thread_id` int(10) unsigned NOT NULL,
`message` mediumtext collate utf8_unicode_ci NOT NULL,
PRIMARY KEY (`thread_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
as you can see, the message content is in a separated table,
now this query normaly is completed in 0.0005 which is shown by codeigniter profiling
bu somethimes it takes up to 25.0050 sec
i have a posts table but the text field is not in a seperated table and it always gives a number close to 0.0020
is there a way to imporve this query please ?
EXPLAIN SHOW's
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t const PRIMARY PRIMARY 3 const 1
1 SIMPLE t_data const PRIMARY PRIMARY 4 const 1
1 SIMPLE user const PRIMARY PRIMARY 4 const 1

Answer 1

I guess that time oscillation it's cache related.
Try to use query profiler
Use explain directive for further details
Take a look at top 10 SQL Performance tips