Here's what I found about Q2A related questions script. After following a chain of functions, the deep-down MySQL query is this:
JOIN (SELECT postid, SUM(score)+LOG(postid)/1000000 AS score FROM ((SELECT ^titlewords.postid, LOG(#/titlecount) AS score FROM ^titlewords JOIN ^words ON ^titlewords.wordid=^words.wordid JOIN ^titlewords AS source ON ^titlewords.wordid=source.wordid WHERE source.postid=# AND titlecount<#) UNION ALL (SELECT ^posttags.postid, 2*LOG(#/tagcount) AS score FROM ^posttags JOIN ^words ON ^posttags.wordid=^words.wordid JOIN ^posttags AS source ON ^posttags.wordid=source.wordid WHERE source.postid=# AND tagcount<#) UNION ALL (SELECT ^posts.postid, LOG(#/^categories.qcount) FROM ^posts JOIN ^categories ON ^posts.categoryid=^categories.categoryid AND ^posts.type='Q' WHERE ^categories.categoryid=(SELECT categoryid FROM ^posts WHERE postid=#) AND ^categories.qcount<#)) x WHERE postid!=# GROUP BY postid ORDER BY score DESC LIMIT #) y ON ^posts.postid=y.postid";
You can't expect a fast performance with this lengthy code. I think maybe this adds to performance when you list more related questions. I'm still struggling because when I reduce the number of related questions, less Adsense ads are shown. Maybe I will try to make a different thing that is simpler in term of server requests, but with more texts for Google adsense.
