query extremely slow after migration to mysql 5.7 - mysql

Question

I have a MySQL database with InnoDB tables summing up over 10 ten GB of data that I want to migrate from MySQL 5.5 to MySQL 5.7. And I have a query that looks a bit like:
SELECT dates.date, count(mySub2.myColumn1), sum(mySub2.myColumn2)
FROM (
SELECT date
FROM dates -- just a table containing all possible dates next 5 years
WHERE date BETWEEN '2016-06-01' AND '2016-09-03'
) AS dates
LEFT JOIN (
SELECT o.id, time_start, time_end
FROM order AS o
INNER JOIN order_items AS oi on oi.order_id = o.id
WHERE time_start BETWEEN '2016-06-01' AND '2016-09-03'
) AS mySub1 ON dates.date >= mySub1.time_start AND dates.date < mySub1.time_end
LEFT JOIN (
SELECT o.id, time_start, time_end
FROM order AS o
INNER JOIN order_items AS oi on oi.order_id = o.id
WHERE o.shop_id = 50 AND time_start BETWEEN '2016-06-01' AND '2016-09-03'
) AS mySub2 ON dates.date >= mySub2.time_start AND dates.date < mySub2.time_end
GROUP BY dates.date;
My problem is that this query is performing fast in MySQL 5.5 but extremely slow in MySQL 5.7.
In MySQL 5.5 it is taking over 1 second at first and < 0.001 seconds every recurring execution without restarting MySQL.
In MySQL 5.7 it is taking over 11.5 seconds at first and 1.4 seconds every recurring execution without restarting MySQL.
And the more LEFT JOINs I add to the query, the slower the query becomes in MySQL 5.7.
Both instances now run on the same machine, on the same hard drive and with the same my.ini settings. So it isn't hardware.
The execution plans do differ, though and I don't know what to make from it.
This is the EXPLAIN EXTENDED on MySQL 5.5:
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | extra |
|----|-------------|------------|-------|---------------|-------------|---------|-----------|-------|----------|---------------------------------|
| 1 | PRIMARY | dates | ALL | | | | | 95 | 100.00 | Using temporary; Using filesort |
| 1 | PRIMARY | <derived2> | ALL | | | | | 281 | 100.00 | '' |
| 1 | PRIMARY | <derived3> | ALL | | | | | 100 | 100.00 | '' |
| 3 | DERIVED | o | ref | xxxxxx | shop_id_fk | 4 | '' | 1736 | 100.00 | '' |
| 3 | DERIVED | oc | ref | xxxxx | order_id_fk | 4 | myDb.o.id | 1 | 100.00 | Using index |
| 2 | DERIVED | o | range | xxxx | date_start | 3 | | 17938 | 100.00 | Using where |
| 2 | DERIVED | oc | ref | xxx | order_id_fk | 4 | myDb.o.id | 1 | 100.00 | Using where |
This is the EXPLAIN EXTENDED on MySQL 5.7:
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | extra |
|----|-------------|-------|--------|---------------|-------------|---------|------------------|------|----------|----------------|
| 1 | SIMPLE | dates | ALL | | | | | 95 | 100.00 | Using filesort |
| 1 | SIMPLE | oi | ref | xxxxxx | order_id_fk | 4 | const | 228 | 100.00 | |
| 1 | SIMPLE | o | eq_ref | xxxxx | PRIMARY | 4 | myDb.oi.order_id | 1 | 100.00 | Using where |
| 1 | SIMPLE | o | ref | xxxx | shop_id_fk | 4 | const | 65 | 100.00 | Using where |
| 1 | SIMPLE | oi | ref | xxx | order_id_fk | 4 | myDb.o.id | 1 | 100.00 | Using where |
I want to understand why the MySQLs treat the same query that much different, and how I can tweak MySQL 5.7 to be faster?
I'm not looking for help on rewriting the query to be faster, as that is something I am already doing on my own.

Answer 1

As can be read in the comments, #wchiquito has suggested to look at the optimizer_switch. In here I found that the switch derived_merge could be set to off, to fix this new, and in this specific case undesired, behaviour.
set session optimizer_switch='derived_merge=off'; fixes the problem.
(This can also be done with set global ... or be put in the my.cnf / my.ini)

Answer 2

Building and maintaining a "Summary Table" would make this query run much faster than even 1 second.
Such a table would probably include shop_id, date, and some count.
More on summary tables.

Answer 3

I too faced slow query execution issue after migrating to mysql 5.7 and in my case, even setting session optimizer_switch to 'derived_merge=off'; didn't help.
Then, I followed this link: https://www.saotn.org/mysql-innodb-performance-improvement/ and the query's speed became normal.
To be specific my change was just setting these four parameters in my.ini as described in the link:
innodb_buffer_pool_size
innodb_buffer_pool_instances
innodb_write_io_threads
innodb_read_io_threads