Scream,
I notice the increased use of LEFT (outer) joins in 5.08. While I appreciate the simplicity of db structure and coding this provides, I have always worked under the assumption that you take a performance hit when using these types of joins.
Because the query has to execute against both tables and you are not using a pre-built index, you are effectively performing two queries against the entire tables and a sort for every query that you submit (as I understand it - I could be wrong).
While it does not matter for small tables, and so should not matter for the category or boards tables, IMHO I think you should restrict LO joins to a minimum - and avoid them alltogther on the posts table.
I've actually seen a major application brought to it's knees through a single LEFT join.
Hope this is useful.
Dave.
