GameMusic

Most likely your SQL is invalid for your tables.  Post the query.

EXPLAIN SELECT COUNT( * ) FROM boardposts t1 INNER JOIN boardposts t2 ON ( t2.topic =766 AND t2.replyTo =47069 ) WHERE t1.topic =766 AND ( t1.replyTo = t2.id OR t1.id = t2.id ) ORDER BY t1.addDate LIMIT 0 , 20 [code]id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref id_2,byTopic,byReplyTo byTopic 4 const 12943 Using where; Using filesort 1 SIMPLE t2 ref id_2,byTopic,byReplyTo byReplyTo 4 const 7185 Using where 1  SIMPLE  t1  ref  id_2,byTopic,byReplyTo  byTopic  4  const  12943  Using where 1 SIMPLE t2 ref id_2,byTopic,byReplyTo byReplyTo 4 const 7185 Using where[/code] The first 2 are the data query, and the second 2 are the count query topic = id of the topic replyTo = id of the post that post is a reply to

Try preg_replace_callback too.

SELECT t1.* FROM boardposts t1 INNER JOIN boardposts t2 ON ( t2.topic =766 AND t2.replyTo = 47069 ) WHERE t1.topic = 766 AND (t1.replyTo = t2.id OR t1.id = t2.id) ORDER BY t1.addDate LIMIT 0 , 20 I'm selecting a post and each reply to that post, and replies to those replies.  This query runs slowly (3 to 4 seconds) on a huge topic (12,000 replies) when selecting the first post. But the weird thing is, if I try to find the COUNT(*) or COUNT(t1.*) (for the purpose of pagination) the query runs a LONG time and the entire boardposts table is locked until I stop the process.  This doesn't make sense to me because I'd assume an internal counter would be faster than returning the data.