Question

so I have a 560mb db with the largest table 500mb(over 10 million rows)

my query hase to join 5 tables and takes about 10 seconds to finish….

SELECT DISTINCT trips.tripid                                AS tripid,
                stops.stopdescrption                        AS "perron",
                Date_format(segments.segmentstart, "%H:%i") AS "time",
                Date_format(trips.tripend, "%H:%i")         AS "arrival",
                Upper(routes.routepublicidentifier)         AS "lijn",
                plcend.placedescrption                      AS "destination"
FROM   calendar
       JOIN trips
         ON calendar.vsid = trips.vsid
       JOIN routes
         ON routes.routeid = trips.routeid
       JOIN places plcstart
         ON plcstart.placeid = trips.placeidstart
       JOIN places plcend
         ON plcend.placeid = trips.placeidend
       JOIN segments
         ON segments.tripid = trips.tripid
       JOIN stops
         ON segments.stopid = stops.stopid
WHERE  stops.stopid IN ( 43914, 23899, 23925, 23908,
                         23913, 19899, 23871, 43902,
                         23876, 25563, 18956, 19912,
                         23889, 23861, 23879, 23884,
                         23856, 19920, 19898, 23916,
                         23894, 20985, 23930, 20932,
                         20986, 22434, 20021, 19893,
                         19903, 19707, 19935 )
       AND calendar.vscdate = Str_to_date('25-10-2011', "%e-%c-%Y")
       AND segments.segmentstart >= Str_to_date('15:56', "%H:%i")
       AND routes.routeservicetype = 0
       AND segments.segmentstart > "00:00:00"
ORDER  BY segments.segmentstart 

what are things I can do to speed this up? any tips are welcome, i’m pretty new to sql…
but I can’t change the structure of the db because it’s not mine…

Answer 1

Just looking at the query, I would say that you should make sure that you have indexes on trips.vsid, calendar.vscdate, segments.segmentstart and routes.routeservicetype. I assume that there is already indexes on all the primary keys in the tables.

Using explain as Briedis suggested would show you how well the indexes work.

You might want to add covering indexes for some tables, like for example an index on trips.vsid where tripid and routeid are included. That way the database can use only the index for the data that is needed from the table, and not read from the actual table.

Edit:

The execution plan tells you that it successfully uses indexes for everything except the segments table, where it does a table scan and filters by the where condition. You should try to make a covering index for segments.segmentstart by including tripid and stopid.