Mysql – Think I have the right indexes and query, but MySQL Query is still slow

table_1

id | column_1 | import_date

Indexes: Mutli-column key (multi_column) of import_date and column_1 in addition to an individual index for each column.

table_2

id | column_1 | column_2

Indexes: Multi-column key (multi_column) for column_1 and column_2 in addition to an individual index for each column.

i.e. both tables have two composite indexes (of the same name in this question) as well as separate indexes.

Query

I've tried flipping the query around and playing with using/forcing different indexes but it didn't seem to help.

SELECT table_1.import_date, count(*) AS count
FROM table_1
FORCE INDEX (import_date)
JOIN table_2 USE INDEX (multi_column) ON table_1.column_1 = table_2.column_1 AND column_2 = "Some String"
WHERE table_1.import_date >= '2016-05-26'
GROUP BY table_1.import_date
LIMIT 365

I tried adding in the LIMIT and a where clause to check where the date was greater than the same date last year just to try and prevent a large number of results and filter but neither seemed to improve the performance of the query, both tables have a large record set.

EXPLAIN

id  select_type table   partitions  type    possible_keys   key key_len ref rows    filtered    Extra
1   SIMPLE  table_1 NULL    range   multi_column,import_date    import_date 6   NULL    1932171 100.00  Using index condition; Using where
1   SIMPLE  table_2 NULL    ref multi_column    multi_column    126 table_1.column_1,const  117 100.00  Using index

Sorry for obfuscated table and column names, trying to keep it simple.

Original Explain without force/use:

id  select_type table   partitions  type    possible_keys   key key_len ref rows    filtered    Extra
1   SIMPLE  table_1 NULL    index   multi_column,column_1,import_date   import_date 69  NULL    365 100.00  Using where; Using index
1   SIMPLE  table_2 NULL    ref multi_column,column_1,column_2  multi_column    126 table_1.column_1,const  117 100.00  Using index

Row counts for each table are 3,937,236 and 4,503,551 respectively.

The query currently takes around 80s, how long should it take, I'm not sure but I imagined with indexes then hopefully under a second.

Running locally on my development machine just now, Mac OS X El Capitan, 2.2 GHz i7 16gb ram.

MySQL version 5.7.15

Both tables are using InnoDB.

This query seems to take it down to roughly 20 seconds:

select import_date, count(*) as count
from table_1
where exists (select * from table_2 where table_1.column_1 = table_2.column_1 and column_2 = 'Some String')
group by import_date