Question

I got a table with over 6.6 millions rows.

I got a field, named trip_id who’s in BINARY(16). I find my query too slow (0.2 seconds). This query run near once every 3 seconds.

Before doing anything stupid, I want to know if I lower the index size on trip_id from full to 12, would it make a difference ?

If I try to tweak my query more, would it make a difference ?

Thanks

EDIT:

Query :

SELECT      stop_times.stop_id
FROM        trips
LEFT JOIN   stop_times ON trips.trip_id = stop_times.trip_id
WHERE       trips.route_id  = '141'
GROUP BY    stop_times.stop_id
ORDER BY    trips.trip_headsign ASC,
            stop_times.stop_sequence ASC

trip_id BINARY(16)

route_id SMALLINT(3)

trip_headsign VARCHAR(50)

stop_sequence SMALLINT(3)

Explain of the query :

Answer 1

After doing researches, I’ve found the problem because yes, 0.2 seconds is slow.

SELECT      t.trip_headsign, st.stop_sequence, s.stop_code, s.stop_name
FROM        stop_times AS st
JOIN        stops AS s USING (stop_id)
JOIN        (   SELECT  trip_id,
                        route_id,
                        trip_headsign
                FROM    trips
                WHERE   route_id = '141'
                LIMIT   2
            ) AS t
WHERE       t.trip_id = st.trip_id
GROUP BY    st.stop_id

First, instead of doing a LEFT JOIN, JOIN is faster here. But the important point, I was matching all results from trips in the WHERE statement.

However, since a bus can only have 2 directions, I only have to limit my results to 2. Now, my results are near 0.018. Over 1000% improvement.