why my sql query slow? - mysql

Question

I try to create a view which join from 4 tables (tb_user is 200 row, tb_transaction is 250.000 row, tb_transaction_detail is 250.000 row, tb_ms_location is 50 row),
when i render with datatables serverside, it's take 13 secons. even when I filtering it.
I don't know why it's take too long...
here my sql query
CREATE VIEW `vw_cashback` AS
SELECT
`tb_user`.`nik` AS `nik`,
`tb_user`.`full_name` AS `nama`,
`tb_ms_location`.`location_name` AS `lokasi`,
`tb_transaction`.`date_transaction` AS `tanggal_setor`,
sum(CASE WHEN `tb_transaction_detail`.`vehicle_type`=1 THEN 1 ELSE 0 END) AS `mobil`,
sum(CASE WHEN `tb_transaction_detail`.`vehicle_type`=2 THEN 1 ELSE 0 END) AS `motor`,
sum(CASE WHEN `tb_transaction_detail`.`vehicle_type`=3 THEN 1 ELSE 0 END) AS `truck`,
sum(CASE WHEN `tb_transaction_detail`.`vehicle_type`=4 THEN 1 ELSE 0 END) AS `speda`,
sum(`tb_transaction_detail`.`total`) AS `total_global`,
(sum(`tb_transaction_detail`.`total`) * 0.8) AS `total_user`,
(sum(`tb_transaction_detail`.`total`) * 0.2) AS `total_tgr`,
((sum(`tb_transaction_detail`.`total`) * 0.2) / 2) AS `total_cashback`,
(curdate() - cast(`tb_user`.`created_at` AS date)) AS `status`
FROM `tb_user`
JOIN `tb_transaction` ON `tb_user`.`id` = `tb_transaction`.`user_id`
JOIN `tb_transaction_detail` ON `tb_transaction`.`id` = `tb_transaction_detail`.`transaction_id`
JOIN `tb_ms_location` ON `tb_ms_location`.`id` = `tb_transaction`.`location_id`
GROUP BY
`tb_user`.`id`,
`tb_transaction`.`date_transaction`,
`tb_user`.`nik`,
`tb_user`.`full_name`,
`tb_user`.`created_at`,
`tb_ms_location`.`location_name`
thanks

Answer 1

The unfiltered query must be slow, because it takes all records from all tables, joins and aggregates them.
But you say the view is still slow when you filter. The question is: How do you filter? As you are aggregating by user, location and transaction date, it should be one of these. However, you don't have the user ID or the transaction ID in your result list. This doesn't feel natural and I'd suggest you add them, so a query like
select * from vw_cashback where user_id = 5
or
select * from vw_cashback where transaction_id = 12345
would be possible.
As is, you'd have to filter by location name or user nik / name. So if you want it thus, then create Indexes for the lookup:
CREATE idx_location_name ON tb_ms_location(location_name, id)
CREATE idx_user_name ON tb_user(full_name, id)
CREATE idx_user_nik ON tb_user(nik, id)
The latter two can even be turned into covering indexs (i.e. indexes containing all columns used in the query) that may still speed up the process:
CREATE idx_user_name ON tb_user(nik, id, full_name, created_at);
CREATE idx_user_nik ON tb_user(full_name, id, nik, created_at);
As for the access via index, you also may want covering indexes:
CREATE idx_location_id ON tb_ms_location(id, location_name)
CREATE idx_user_id ON tb_user(id, nik, full_name, created_at);