Mysql slow query on large table - mysql

Question

With Mysql 5.6.10, I have a table like this:
CREATE TABLE `es_user_action` (
`id` bigint(11) unsigned NOT NULL AUTO_INCREMENT,
`user_id` bigint(11) unsigned NOT NULL,
`company_id` bigint(11) unsigned NOT NULL,
`work_id` bigint(11) unsigned NOT NULL,
`action` tinyint(2) NOT NULL COMMENT '10, 20, 30, 40',
`action_id` bigint(11) unsigned DEFAULT NULL,
`apply_id` bigint(11) unsigned DEFAULT '0',
`apply_display_id` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`action_time` datetime NOT NULL,
`scout_time` datetime NOT NULL,
`register_datetime_sorting` datetime DEFAULT NULL,
`score` tinyint(2) DEFAULT '0',
`is_pending` tinyint(2) DEFAULT '0',
`apply_status` tinyint(2) DEFAULT '2' COMMENT '1: paid, 2: free',
`has_response` tinyint(2) DEFAULT '0',
`response_time` datetime DEFAULT NULL,
`is_shown` tinyint(2) DEFAULT '1',
`source` varchar(15) COLLATE utf8mb4_unicode_ci NOT NULL,
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `user_company_work` (`user_id`,`work_id`,`company_id`,`apply_id`,`source`),
KEY `IDX_2` (`company_id`,`is_shown`,`apply_status`,`apply_id`,`work_id`,`action_time`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=436896779 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
The full query I want to perform on the table would be the following:
SELECT
`id` AS `seqNo`,
`company_id` AS `companyId`,
`work_id` AS `workId`,
`action` AS `userActionType`,
`action_time` AS `userActionDatetime`,
`is_pending`,
`apply_status`,
`action_id`,
`source`,
`user_id` AS `userId`,
`apply_display_id`
FROM
`es_user_action`
WHERE
`company_id` = 449664
AND `is_shown` = 1
AND `apply_status` = 1
AND `apply_id` = 0
AND `action_time` >= '2021-01-05 15:56:14'
ORDER BY
is_pending ASC,
action ASC,
score DESC,
CASE
source
WHEN "entenshoku" THEN
action_time
END DESC,
CASE
WHEN source <> "entenshoku" THEN
action_time
END ASC
LIMIT 100 OFFSET 0;
The table has around 15 million rows and the following query takes around 15 seconds. The query becomes very slow.
Can anyone help out? Thanks in advance.
UPDATED:
This is the explain query result:

Answer 1

KEY `IDX_2` (`company_id`,`is_shown`,`apply_status`,`apply_id`,`work_id`,`action_time`)
Work_id is in the way of that index being effective for that SELECT. Remove it. That should speed up the query some. Still the are too many columns and expressions involved in the WHER and ORDER BY to do much more to help.
Changing BIGINTs to smaller INT types will help some (by shrinking the table).

Answer 2

I'm pretty sure that what you have cannot work.
You have is a dynamically changing ORDER BY, depending on the value of source. But which row's source?
If you could decide before issuing the query whether to scan action_time ascending or descending, which value of source would you pick?
Delete this Question, rewrite the query, then open another Question if you still have an issue.