Unnacceptable waitingtime for a left join query. What's wrong?

[Leif Wessman]

Hi!

Please have a look at the following query:

SELECT BOOKS.ISBN, BOOKS.TITLE, IMAGES.WEIGHT, IMAGES.WIDTH
FROM BOOKS
LEFT JOIN IMAGES ON BOOKS.ISBN = IMAGES.ID
WHERE MATCH(BOOKS.TITLE) AGAINST ('mysql database')

BOOKS.ISBN is primary key and IMAGES.ID is primary key

This query USUALLY takes less than 1 sec, but SOMETIMES it can take
about 15 - 25 seconds to complete.

When I remove the LEFT JOIN part the query ALWAYS is very fast.

My MySql version is 3.23.53

When I run EXPLAIN I get the following info:

+--------+----------+---------------+---------+---------+-----------+------+------------+
| table | type | possible_keys | key | key_len | ref |
rows | Extra |
+--------+----------+---------------+---------+---------+-----------+------+------------+
| BOOKS | fulltext | NAME | NAME | 0 | |
1 | where used |
| IMAGES | eq_ref | PRIMARY | PRIMARY | 10 | BOOKS.ISBN|
1 | |
+--------+----------+---------------+---------+---------+-----------+------+------------+

I've tried to optimize both tables, that didn't help.

Any ideas of why the query sometimes takes very long time to finish?

Leif