Whitelisting via SQL lookup to other address book

[Geoff Sweet]

  Greetings everyone, I am running amavisd-new 2.6.4.  It's been very 
stable for me. I would like to try to extend it a little via SQL. The 
vast majority of my virtual users read email via a web interface. That 
interface (horde) provides a fairly robust address book system.  I'm 
hoping that someone could help me understand if it would be possible to 
tune the $sql_select_white_black_list and %sql_clause to look into that 
address book database for whitelisting.

I can see in the structure of the table that the addresses in the 
address book are sorted via the address of the user.  I also can see in 
the documentation how to build a SQL query that will return the same 
format of data as described in the README.sql.txt.  What I am not 
totally clear on is what else I do or don't need to do.

If I add the $sql_select_white_black_list into the amavisd.conf with my 
query, I then need to add the %sql_clause lines as well? Something like 
this:

$sql_select_white_black_list = 'SELECT SOME STUFF';
%sql_clause = (
'sel_wblist' => \$sql_select_white_black_list
);

Correct?  If I understand correctly, anything else in the sql_clause 
that is left out defaults back to whatever is in the cofig file?  Or do 
I have to uncomment the entire %sql_clause block and define the entire 
SQL structure?

Thanks for the help,

-Geoff Sweet