Optimize a SELECT code (vB code)

[Swedie]

I'm having issues on my server with a huge amount of slow queries like this one:

PHP Code:

SELECT postid, visible, userid

                        FROM post AS post

                        WHERE threadid = 124608                              

                                AND visible IN (1

                                ,2

                                )

                        ORDER BY dateline; 


Only thing that changed is the threadid.

I have query times of 20-50 seconds on each of these queries. It's bogging down the server.

So how can that code be optimized further? What about separating the dateline ordering into a php based sorting (array sort).