[wp-hackers] Proper posts_join filters

[Mattias Päivärinta]

Hi guys!
I need to left join the post2cat in my posts_join filter. But I get a 
collision so it seems I'm not the only one. Presently I work around this 
problem using strstr() to check for $wpdb->post2cat in the filter 
parameter. If there's a match I assume there is already a join clause 
equivalent to what I need and attemt to reference that one. But this is 
a less than waterproof hack.
So, what is the proper way of doing posts_join filters?

Mattias