Optimizing MySQL "IN" Select? - mysql

Question

I have the following MySQL query:
SELECT
`influencers`.*,
`locations`.`country_name`
FROM
`influencers`
LEFT JOIN `locations` ON `influencers`.`country_id` = `locations`.`id`
WHERE
`is_dead` = 0
AND `influencers`.`is_private` = 0
AND `influencers`.`country_id` = '31'
AND influencers.uuid IN(
SELECT
`influencer_uuid` FROM `category_influencer`
WHERE
`category_influencer`.`category_id` = 17
AND `category_influencer`.`is_main` = 1)
ORDER BY
`influencers`.`followed_by` DESC
LIMIT 7 OFFSET 6
I have identified the IN subquery is causing a lag of around 10s for this query to complete. Here is the EXPLAIN:
I have indexes on all columns being queried.
How can I significantly speed this query up?
Updated with SHOW CREATE TABLE for both:
locations
CREATE TABLE `locations` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`country_name` varchar(255) DEFAULT NULL,
`city_name` varchar(255) DEFAULT NULL,
`type` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `unique_index` (`city_name`, `country_name`),
KEY `type` (`type`)
USING BTREE) ENGINE = InnoDB AUTO_INCREMENT = 6479 DEFAULT CHARSET = utf8mb4
influencers
CREATE TABLE `influencers` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`bio` varchar(255) CHARACTER
SET utf8mb4 DEFAULT NULL,
`url` varchar(255) CHARACTER
SET utf8mb4 DEFAULT NULL,
`followed_by` int(11) DEFAULT NULL,
`follows` int(11) DEFAULT NULL,
`full_name` varchar(255) CHARACTER
SET utf8mb4 NOT NULL,
`social_id` varchar(255) DEFAULT NULL,
`is_private` tinyint (1) DEFAULT NULL,
`avatar` varchar(255) NOT NULL,
`username` varchar(30) NOT NULL,
`text_search` text CHARACTER
SET utf8mb4 NOT NULL,
`updated_at` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
`uuid` varchar(255) DEFAULT NULL,
`is_dead` tinyint (4) DEFAULT NULL,
`country_id` int(11) DEFAULT NULL,
`city_id` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `username` (`username`),
UNIQUE KEY `uuid` (`uuid`),
KEY `is_dead` (`is_dead`),
KEY `updated_at` (`updated_at`),
KEY `followed_by` (`followed_by`),
KEY `social_id` (`social_id`),
KEY `is_private` (`is_private`),
KEY `country_id` (`country_id`),
FULLTEXT KEY `text_search` (`text_search`)) ENGINE = InnoDB AUTO_INCREMENT = 2278376 DEFAULT CHARSET = utf8

Answer 1

You could avoid the in clause using an inner join
SELECT
`influencers`.*,
`locations`.`country_name`
FROM
`influencers`
INNER JOIN (
SELECT
`influencer_uuid` FROM `category_influencer`
WHERE
`category_id` = 17
AND `is_main` = 1
) T ON T.influencer_uuid = influencers.uuid
LEFT JOIN `locations` ON `influencers`.`country_id` = `locations`.`id`
WHERE
`is_dead` = 0
AND `is_private` = 0
AND `country_id` = '31'
ORDER BY
`followed_by` DESC
LIMIT 7 OFFSET 6
This way instead of an iteration on all the IN result you use just a single relational match based on join

Answer 2

Unless I missed something, you can replace the subselect with JOIN:
SELECT influencers.*,
locations.country_name
FROM influencers
JOIN category_influencer T ON (
T.influencer_uuid = influencers.uuid
AND category_id = 17
AND is_main = 1)
LEFT JOIN locations ON influencers.country_id = locations.id
WHERE is_dead = 0
AND is_private = 0
AND country_id = '31'
ORDER BY followed_by DESC
LIMIT 7 OFFSET 6