mysql group by joined column too slow - mysql

Question

I have two tables events and event_params
the first table stores the events with these columns
events | CREATE TABLE `events` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`project` varchar(24) NOT NULL,
`event` varchar(24) NOT NULL,
`date` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`),
KEY `project` (`project`,`event`)
) ENGINE=InnoDB AUTO_INCREMENT=2915335 DEFAULT CHARSET=latin1
and second stores parameters for each event with these columns
event_params | CREATE TABLE `event_params` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`event_id` int(10) unsigned NOT NULL,
`name` varchar(24) NOT NULL,
`value` varchar(524) CHARACTER SET utf8 NOT NULL,
PRIMARY KEY (`id`),
KEY `name` (`name`),
KEY `event_id` (`event_id`),
KEY `value` (`value`),
) ENGINE=InnoDB AUTO_INCREMENT=20789391 DEFAULT CHARSET=latin1
now I want to get count of events those have various values on a specified parameter
I wrote this query for campaign parameter but this is too slow (15 secs to respond)
SELECT
event_params.value as campaign,
count(*) as count
FROM `events`
left join event_params on event_params.event_id = events.id
and event_params.name = 'campaign'
WHERE events.project = 'foo'
GROUP by event_params.value
and here is the EXPLAIN query result:
+----+-------------+--------------+------------+------+---------------------+----------+---------+------------------+------+----------+----------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+--------------+------------+------+---------------------+----------+---------+------------------+------+----------+----------------------------------------------+
| 1 | SIMPLE | events | NULL | ref | project | project | 26 | const | 1 | 100.00 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | event_params | NULL | ref | name,event_id,value | event_id | 4 | events.events.id | 4 | 100.00 | Using where |
+----+-------------+--------------+------------+------+---------------------+----------+---------+------------------+------+----------+----------------------------------------------+
can i speed up this query ?

Answer 1

You may try adding the following index on the event_params table, which might speed up the join:
CREATE INDEX idx1 ON event_params (event_id, name, value);
The aggregation step probably can't be optimized much because the COUNT operation involves counting each record.

Answer 2

Move the "campaign value" into the main table, with a suitable length for VARCHAR and then
SELECT
campaign,
count(*) as count
FROM `events`
WHERE project = 'foo'
GROUP by campaign
And have
INDEX(project, campaign)
A bit of advice when tempted to use EAV: Move the 'important' values into the main table; leave only the rarely used or rarely set 'values' in the other table. Also (assuming there are no dups), have
PRIMARY KEY(event_id, name)
More discussion: http://mysql.rjweb.org/doc.php/eav