help understanding the query optimizer

[Federico Bertola]

Hi,

I'm trying to understand the query optimizer for research purpose. As 
the codebase is quite huge, I would like some advice, i.e. where to look 
and what tests should I inspect.
What I really trying to do is to isolate the query optimizer so that I 
could get and show a plan without the need to execute the query with a 
full db stack. Of course this would require some wrapping but I think it 
is doable.

Thanks a lot for your help!

Best regards,
Federico.