SQL: Refactoring a multi-join query - mysql

Question

I have a query that should be quite simple and yet it causes me a lot of headaches.
I have a simple ads system that requires filtering ads according to a few variables.
I need to limit the number of views/clicks per day and the total number of views/clicks for a given ad. Also each ad is linked to one or more slots in which the ad can appear. I have a table that saves the statistics that I need about each ad. Note that the statistics table changes very frequently.
These are the tables that I'm using:
CREATE TABLE `t_ads` (
`id` int(10) unsigned NOT NULL auto_increment,
`name` varchar(255) NOT NULL,
`content` text NOT NULL,
`is_active` tinyint(1) unsigned NOT NULL,
`start_date` date NOT NULL,
`end_date` date NOT NULL,
`max_views` int(10) unsigned NOT NULL,
`type` tinyint(3) unsigned NOT NULL default '0',
`refresh` smallint(5) unsigned NOT NULL default '0',
`max_clicks` int(10) unsigned NOT NULL,
`max_daily_clicks` int(10) unsigned NOT NULL,
`max_daily_views` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE `t_ad_slots` (
`id` int(10) unsigned NOT NULL auto_increment ,
`name` varchar(255) NOT NULL,
`width` int(10) unsigned NOT NULL,
`height` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE `t_ads_to_slots` (
`ad_id` int(10) unsigned NOT NULL,
`slot_id` int(10) unsigned NOT NULL,
`value` int(10) unsigned NOT NULL,
PRIMARY KEY (`ad_id`,`slot_id`),
KEY `slot_id` (`slot_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
ALTER TABLE `t_ads_to_slots`
ADD CONSTRAINT `t_ads_to_slots_ibfk_1` FOREIGN KEY (`ad_id`) REFERENCES `t_ads` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION,
ADD CONSTRAINT `t_ads_to_slots_ibfk_2` FOREIGN KEY (`slot_id`) REFERENCES `t_ad_slots` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION;
CREATE TABLE `t_ad_stats` (
`ad_id` int(10) unsigned NOT NULL,
`slot_id` int(10) unsigned NOT NULL,
`date` date NOT NULL COMMENT,
`views` int(10) unsigned NOT NULL,
`unique_views` int(10) unsigned NOT NULL,
`clicks` int(10) unsigned NOT NULL default '0',
PRIMARY KEY (`ad_id`,`slot_id`,`date`),
KEY `slot_id` (`slot_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
ALTER TABLE `t_ad_stats`
ADD CONSTRAINT `t_ad_stats_ibfk_1` FOREIGN KEY (`ad_id`) REFERENCES `t_ads` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION,
ADD CONSTRAINT `t_ad_stats_ibfk_2` FOREIGN KEY (`slot_id`) REFERENCES `t_ad_slots` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION;
This is the query that I use to get ads for a given slot (Note that in this example I hard coded 20 as the slot id and 0,1,2 as the ad type, I get this data from a php script which invokes this query)
SELECT `ads`.`content`, `slots`.`value`, `ads`.`id`, `ads`.`refresh`, `ads`.`type`,
SUM(`total_stats`.`views`) AS "total_views",
SUM(`total_stats`.`clicks`) AS "total_clicks"
FROM (`t_ads` AS `ads`,
`t_ads_to_slots` AS `slots`)
LEFT JOIN `t_ad_stats` AS `total_stats`
ON `total_stats`.`ad_id` = `ads`.`id`
LEFT JOIN `t_ad_stats` AS `daily_stats`
ON (`daily_stats`.`ad_id` = `ads`.`id`) AND
(`daily_stats`.`date` = CURDATE())
WHERE (`ads`.`id` = `slots`.`ad_id`) AND
(`ads`.`type` IN(0,1,2)) AND
(`slots`.`slot_id` = 20) AND
(`ads`.`is_active` = 1) AND
(`ads`.`end_date` >= NOW()) AND
(`ads`.`start_date` <= NOW()) AND
((`ads`.`max_views` = 0) OR
(`ads`.`max_views` > "total_views")) AND
((`ads`.`max_clicks` = 0) OR
(`ads`.`max_clicks` > "total_clicks")) AND
((`ads`.`max_daily_clicks` = 0) OR
(`ads`.`max_daily_clicks` > IFNULL(`daily_stats`.`clicks`,0))) AND
((`ads`.`max_daily_views` = 0) OR
(`ads`.`max_daily_views` > IFNULL(`daily_stats`.`views`,0)))
GROUP BY (`ads`.`id`)
I believe that this query is self explanatory, even though its quite long. Note that the MySQL version that I'm using is: 5.0.51a-community. It seems to me like the big issue here is the double join to the stats table (I did that so that I will be able to get the data from a specific record and from multiple records (sum)).
How would you implement this query in order to get better results? (Note that I can't change from InnoDB).
Hopefully everything is clear about my question, but if that is not the case, please ask and I will clarify.
Thanks in advance,
Kfir

Answer 1

Add indexes to following columns:
t_ads.is_active
t_ads.start_date
t_ads.end_date
Change the order of the primary key on t_ad_stats to:
(`ad_id`,`date`,`slot_id`)
or add a covering index to t_ad_stats
('ad_id', 'date')
Change from 0 meaning "no limit" to 2147483647 meaning no limit, so you can change things like:
((`ads`.`max_views` = 0) OR (`ads`.`max_views` > "total_views"))
to
(`ads`.`max_views` > "total_views")
You could greatly improve this is if you were keeping running totals instead of having to calculate them each time.

Answer 2

Expanding on a comment above I believe that the following columns should be indexed:
ads.id
ads.type
ads.start_date
ads.end_date
daily_stats.date
As well as these:
slots.slot_id
ads.is_active
And these as well:
ads.max_views
ads.max_clicks
ads.max_daily_clicks
ads.max_daily_views
daily_stats.clicks
daily_stats.views
Do note that applying indexes on these columns will speed up your SELECTs but slow down your INSERTs since the indexes will need updating as well. But, you don't have to apply all of this all at once. You can do it incrementally and see how the performance shakes out for selects as well as inserts. If you cannot find a good middleground then I would suggest denormalization.