Why this query is to slow in mysql - mysql

Question

I try to improve this query but I do not made successefully. I use a some left join and subquerys (I don't know another form) We try to get all bookings from users with certain status and the number of bookings multiples related with this booking and get from the log user the origin. The query is slow even if use a limit clausure. I Appreciate all the help can you give me.
This is the query:
SELECT DISTINCT b.uneaque_id, b.id, b.status, b.route_status, b.username, b.purpose, b.transfer, b.pickup_date, b.pickup_time, b.return_time, b.amount, b.default_location, b.start_address_route_comments, b.start_address_route, b.end_address_route_comments, b.end_address_route, u1.first_name, u1.last_name, b.transaction_Id, b.manual_payment, mr.AddressCount, lu.origin
FROM bookingdetails b
LEFT JOIN log_users lu ON lu.uneaque_id = b.uneaque_id AND lu.command_type = 'NEW BOOKING'
LEFT JOIN (
SELECT booking_id, COUNT(*) AS AddressCount FROM booking_multiple_rides GROUP BY booking_id
) mr ON b.id = mr.booking_id,
userdetails u1 WHERE b.username = u1.email
AND u1.user_status IN ('Active', 'Blocked', 'Not_Active')
AND b.default_location = 1
PD: Sorry for my english.

Answer 1

You have a ON b.id = mr.booking_id, userdetails u1 WHERE
you should change with a proper inner join
SELECT DISTINCT b.uneaque_id
, b.id, b.status
, b.route_status
, b.username
, b.purpose
, b.transfer
, b.pickup_date
, b.pickup_time
, b.return_time
, b.amount
, b.default_location
, b.start_address_route_comments
, b.start_address_route
, b.end_address_route_comments
, b.end_address_route
, u1.first_name
, u1.last_name
, b.transaction_Id
, b.manual_payment
, mr.AddressCount
, lu.origin
FROM bookingdetails b
LEFT JOIN log_users lu ON lu.uneaque_id = b.uneaque_id AND lu.command_type = 'NEW BOOKING'
LEFT JOIN (
SELECT booking_id
, COUNT(*) AS AddressCount
FROM booking_multiple_rides GROUP BY booking_id
) mr ON b.id = mr.booking_id
INNER JOIN userdetails u1 ON b.username = u1.email
AND u1.user_status IN ('Active', 'Blocked', 'Not_Active')
AND b.default_location = 1
and be sure you have proper index on
table bookingdetails a composite index on columns ( uneaque_id , id, default_location)
table log_users a composite index on columns (uneaque_id, command_type)
table userdetails a cmposite index on columns (email,user_status )

Answer 2

Tip 1.
Hiding a derived table in a LEFT JOIN is a prescription for sluggishness.
Replace
mr.AddressCount
with
( SELECT COUNT(*)
FROM booking_multiple_rides
WHERE booking_id = b.id
GROUP BY booking_id ) AS AddressCount
and get rid of the LEFT JOIN ( SELECT ... ) AS mr ON ..
Tip 2 Use explicit JOINs, no the old-fashioned "comma-join":
JOiN userdetails u1
ON b.username = u1.email
This won't help performance but it will make things clearer.
Tip 3: If you need an INNER JOIN (u1) after a LEFT JOIN, use parentheses. Else, put the inner joins first, then the left joins. This makes it easier to use, but may screw up the logic.
Tip 4: Don't use LEFT unless you need it. When you dont need it, it confuses the reader (and the Optimizer). (Again, no performance change.)
Tip 5: Why are you using DISTINCT? That takes an extra pass over all the resultset.
If those do not help enough, then provide SHOW CREATE TABLE so we can critique the indexes.