mysql NOT EXISTS, very slow - How to improve? - mysql

Question

I've got a small question about trying to ompimise this command I'm running on a table in my database. The table has over 934,836 rows and grows daily by about 12,000.
It holds snapshots of tanks taken daily. What I'm trying to achieve is to see the difference in the snapshots. i.e. see if the player has purchased any new tanks.
The actual snapshot data per account_id is only 100 to 250 rows.
Table wot_snapshots:
CREATE TABLE `wot_snapshots` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`snapshot` varchar(30) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=95 DEFAULT CHARSET=latin1
Table wot_tanks_all:
CREATE TABLE `wot_tanks_all` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`snapshot` int(11) NOT NULL,
`account_id` int(11) NOT NULL,
`tank_id` int(6) NOT NULL,
`wn8` float DEFAULT NULL,
`spotted` int(11) NOT NULL,
`avg_damage_blocked` decimal(6,2) NOT NULL,
`capture_points` int(11) NOT NULL,
`explosion_hits` int(11) NOT NULL,
`piercings` int(11) NOT NULL,
`xp` int(11) NOT NULL,
`survived_battles` int(11) NOT NULL,
`dropped_capture_points` int(11) NOT NULL,
`damage_dealt` int(11) NOT NULL,
`hits_percents` int(11) NOT NULL,
`draws` int(11) NOT NULL,
`battles` int(11) NOT NULL,
`damage_received` int(11) NOT NULL,
`frags` int(11) NOT NULL,
`direct_hits_received` int(11) NOT NULL,
`hits` int(11) NOT NULL,
`battle_avg_xp` int(11) NOT NULL,
`wins` int(11) NOT NULL,
`losses` int(11) NOT NULL,
`piercings_received` int(11) NOT NULL,
`no_damage_direct_hits_received` int(11) NOT NULL,
`shots` int(11) NOT NULL,
`explosion_hits_received` int(11) NOT NULL,
`tanking_factor` decimal(2,2) NOT NULL,
`mark_of_mastery` int(1) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=934837 DEFAULT CHARSET=utf8
Query:
SELECT t1.tank_id, wot_tanks.short_name_i18n FROM wot_tanks_all t1
JOIN wot_tanks ON t1.tank_id = wot_tanks.tank_id
WHERE NOT EXISTS (SELECT tank_id
FROM wot_tanks_all t2
WHERE t1.tank_id = t2.tank_id AND account_id = 527080765 AND snapshot = 60)
AND account_id = 527080765 AND snapshot = 93
Output:
tank_id short_name_i18n
8465 Panther II
53505 T-127
54865 Light VIC
Its currently taking around 30 seconds to run. Am I best to do this all in mysql or offload some of it to PHP?
Any advice and help is greatly appreciated
Thanks,
Jason
Edit: This has just been put together from Google. Still learning!

Answer 1

There is no index on tank id so joining on it will be very slow,I`ve rewritten it to eliminate the self join
SELECT t1.tank_id, wot_tanks.short_name_i18n FROM wot_tanks_all t1
JOIN wot_tanks
ON t1.tank_id = wot_tanks.tank_id
GROUP BY t1.tank_id,wot_tanks.short_name_i18n
HAVING SUM(account_id = 527080765 AND snapshot = 60)=0
AND SUM(account_id = 527080765 AND snapshot = 93)>0
These indexes will speed things up
ALTER TABLE wot_tanks_all ADD KEY(account_id ,snapshot )
ALTER TABLE wot_tanks_all ADD KEY(tank_id )