Query takes more than 40 seconds to execute - mysql

Question

This query takes more than 40 seconds to execute on a table that has 200k rows
SELECT
my_robots.*,
(
SELECT count(id)
FROM hpsi_trading
WHERE estado <= 1 and idRobot = my_robots.id
) as openorders,
apikeys.apikey,
apikeys.apisecret
FROM my_robots, apikeys
WHERE estado <= 1
and idRobot = '2'
and ready = '1'
and apikeys.id = my_robots.idApiKey
and (my_robots.id LIKE '%0'
OR my_robots.id LIKE '%1'
OR my_robots.id LIKE '%2')
I know it is because of the count inside the query, but how could i fix this efficiently.
Edit: Explain
Thanks.

Answer 1

Use GROUP BY instead
SELECT my_robots.*,
count(id) as openorders,
apikeys.apikey,
apikeys.apisecret
FROM my_robots
JOIN apikeys ON apikeys.id = my_robots.idApiKey
LEFT JOIN hpsi_trading ON hpsi_trading.idRobot = my_robots.id and estado <= 1
WHERE estado <= 1 and
idRobot = '2' and
ready = '1' and
(
my_robots.id LIKE '%0' OR
my_robots.id LIKE '%1' OR
my_robots.id LIKE '%2'
)
GROUP BY my_robots.id, apikeys.apikey, apikeys.apisecret
Use explicit JOIN syntax. Some indexes will be needed to run it fast, however, the database structure is not clear from your post (and from your query as well).

Answer 2

The explain plan shows that the largest pain is selecting the data from the table hpsi_trading.
The challenge from the database's point of view is that the query contains a correlated subquery in the SELECT clause, which needs to be executed once for each result of the outer query (after filtering).
Replacing this subquery with a JOIN + GROUP BY will require MySQL to join between all these records (inflate) and only then deflate the data using GROUP BY, which might take time.
Instead, I would extract the subquery to a temporary table, which is grouped during creation, index it and join to it. That way, the subquery will run once, using a quick covering index, it will already group the data and only then join it to the other table.
This far, it's all pros. But, the con here is that extracting a subquery to a temporary table might require more effort on the development side.
Please try this version and let me know if it helped (if not, please provide a fresh EXPLAIN plan screenshot):
Creating the temp table:
CREATE TEMPORARY TABLE IF NOT EXISTS temp1 AS
SELECT idRobot, COUNT(id) as openorders
FROM hpsi_trading
WHERE estado <= 1
GROUP BY idRobot;
The modified query:
SELECT
my_robots.*,
temp1.openorders,
apikeys.apikey,
apikeys.apisecret
FROM
my_robots,
apikeys
LEFT JOIN temp1 on temp1.idRobot = my_robots.id
WHERE
estado <= 1 AND idRobot = '2'
AND ready = '1'
AND apikeys.id = my_robots.idApiKey
AND (my_robots.id LIKE '%0'
OR my_robots.id LIKE '%1'
OR my_robots.id LIKE '%2')
The indexes to add for this solution (I assumed from logic that estado, idRobot and ready are from the apikeys table. If that's not the case, let me know and I'll adjust the indexes):
ALTER TABLE `temp1` ADD INDEX `temp1_index_1` (idRobot);
ALTER TABLE `hpsi_trading` ADD INDEX `hpsi_trading_index_1` (idRobot, estado, id);
ALTER TABLE `apikeys` ADD INDEX `apikeys_index_1` (`idRobot`, `ready`, `id`, `estado`);
ALTER TABLE `my_robots` ADD INDEX `my_robots_index_1` (`idApiKey`);