Mysql slow query: INNER JOIN + ORDER BY causes filesort

Question

I\'m trying to optimize this query:

SELECT `posts`.* FROM `posts` INNER JOIN `posts_tags` 
     ON `posts`.id = `posts_tags`.post_id 
     WHERE  (((`posts_tags`.         


        

Answer 1

your key index_posts_on_created_at is sorted ascending but you want results sorted descending