Question

Apologies if this has been asked before but is there any way, at all, I can optimize this query to run faster. At the minute it takes about 2 seconds which while isn’t a huge amount it is the slowest query on my site, all other queries take less that 0.5 secs.

Here is my query:

SELECT SQL_CALC_FOUND_ROWS MAX(images.id) AS maxID, celebrity.* FROM images
JOIN celebrity ON images.celeb_id = celebrity.id
GROUP BY images.celeb_id
ORDER BY maxID DESC
LIMIT 0,20

Here is an explain:

1 SIMPLE celebrity ALL PRIMARY NULL NULL NULL 536 Using temporary; Using filesort
1 SIMPLE images ref celeb_id celeb_id 4 celeborama_ignite.celebrity.id 191

I’m at a loss at how to improve the performance in this query further. I’m not super familiar with MySQL, but I do know that it is slow because I am sorting on the data created by MAX() and that has no index. I can’t not sort on that as it gives me the results needed, but is there something else I can do to prevent it from slowing down the query?

Thanks.

Answer 1

If you really need fast solution – then don’t perform such queries in runtime.

Just create additional field last_image_id in celebrity table and update it on event of uploading of new image (by trigger or your application logic, doesn’t matter)