MySQL query runs very slow - mysql

Question

I have a MySQL (v5.7.26) query that runs forever. Here is the query:
SELECT
ur.user_id AS user_id,
sum(r.duration) AS total_time,
count(user_id) AS number_of_workouts
FROM user_resource ur
INNER JOIN resource r ON r.id = ur.resource_id
WHERE
ur.status = 1
AND NOT ur.action_date IS NULL
AND ur.user_id IN (
SELECT user_id
FROM user_resource ur2
WHERE ur2.action_date >= now() - INTERVAL 2 DAY
)
AND r.type = 'WORKOUT'
GROUP BY ur.user_id;
I have played a bit with it, by trying to understand where is the problem. For the testing purposes, I tried breaking in two. So:
SELECT user_id
FROM user_resource ur2
WHERE ur2.action_date >= now() - INTERVAL 2 DAY;
That returns (very quickly) list of user user_id's.
When I plug the returned result in to the first part of the query, like this:
SELECT
ur.user_id AS user_id,
sum(r.duration) AS total_time,
count(user_id) AS number_of_workouts
FROM user_resource ur
INNER JOIN resource r ON r.id = ur.resource_id
WHERE
ur.status = 1
AND NOT ur.action_date IS NULL
AND ur.user_id IN (1,1,1,4,4,5,6,7,7,7);
AND r.type = 'WORKOUT'
GROUP BY ur.user_id
It runs very fast. My assumption is the IN (Subquery) is the bottleneck.
I was thinking to extract the subquery and get the user_ids, and then used it as a variable, but I am not sure is it the good approach, and additionally I am having issues with it. this is my attempt:
-- first statement
SET #v1 = (SELECT user_id
FROM user_resource ur2
WHERE ur2.action_date >= now() - INTERVAL 2 DAY)
-- second statement
SELECT
ur.user_id AS user_id,
sum(r.duration) AS total_time,
count(user_id) AS prefixes
FROM user_resource ur
INNER JOIN resource r ON r.id = ur.resource_id
WHERE
ur.status = 1
AND NOT ur.action_date IS NULL
AND ur.user_id IN (#v1);
AND r.type = 'WORKOUT'
GROUP BY ur.user_id
Problem here is that the first statement returns an error:
Subquery returns more than 1 row.
Expected result are user_id's, that can be duplicates. And I need those duplicated for the count.
How can I fix this?

Answer 1

Try EXISTS instead of IN
...
AND EXISTS (SELECT *
FROM user_resource ur2
WHERE ur2.user_id = ur.user_id
AND ur2.action_date >= now() - INTERVAL 2 DAY)
...
and indices on user_resource (user_id, action_date), user_resource (status, action_date, user_id) and/or user_resource (type).

Answer 2

You could try:
-- first statement
SET #v1 = (SELECT GROUP_CONCAT(user_id)
FROM user_resource ur2
WHERE ur2.action_date >= now() - INTERVAL 2 DAY)
-- second statement
SELECT
ur.user_id AS user_id,
sum(r.duration) AS total_time,
count(user_id) AS prefixes
FROM user_resource ur
INNER JOIN resource r ON r.id = ur.resource_id
WHERE ur.status = 1 AND NOT ur.action_date IS NULL AND FIND_IN_SET(ur.user_id,#v1)
AND r.type = 'WORKOUT'
GROUP BY ur.user_id

Answer 3

Additional join will be faster then sub-query:
SELECT
ur.user_id AS user_id,
sum(r.duration) AS total_time,
count(user_id) AS number_of_workouts
FROM user_resource ur
INNER JOIN resource r ON r.id = ur.resource_id
INNER JOIN (
SELECT user_id
FROM user_resource ur2
WHERE ur2.action_date >= now() - INTERVAL 2 DAY
) t ON t.user_id = ur.user_id
WHERE
ur.status = 1
AND NOT ur.action_date IS NULL
AND r.type = 'WORKOUT'
GROUP BY ur.user_id;