dovecot - Feb 2014 - Syntax of pattern in map section

I can't seem to find any documentation on the meaning/syntax of the
"pattern" variable in map sections that are found in
dovecot-dict-sql.conf.ext for example. I am trying to setup shared folders.

The only thing[1] I found is:
>>First you'll need to know what kind of dict paths the code uses. ACL
>>plugin uses these paths:
>>
>>shared/shared-boxes/anyone/$owner
>>shared/shared-boxes/user/$user/$owner
>>shared/shared-boxes/group/$group/$owner
What is a "dict path"? Is this some kind of hard coded identifier in
the Dovecot code?

I need to understand how they work because I can't use the example in
http://wiki2.dovecot.org/SharedMailboxes/Shared. This is because in my PostreSQL
table users are not a single column but two columns with the local and domain
part[2]:

        Table "public.shared_mailboxes"
        Column         |          Type          
-----------------------+------------------------
 shared_mailbox_local  | character varying(64)  
 shared_mailbox_domain | character varying(253) 
 shared_to_local       | character varying(64)  
 shared_to_domain      | character varying(253)

How should a map section look in this case?

[1]http://www.dovecot.org/list/dovecot/2009-April/038922.html
[2]I did this in order to use REFERENCES to ensure the user exist.

Kind regards

On Sunday 16 February 2014 17:30:33 da-dovecotlist-15 at abelonline.de
wrote:
> I can't seem to find any documentation on the meaning/syntax of the
> "pattern" variable in map sections that are found in
> dovecot-dict-sql.conf.ext for example. I am trying to setup shared folders.
> I need to understand how they work because I can't use the example in
> http://wiki2.dovecot.org/SharedMailboxes/Shared. This is because in my
> PostreSQL table users are not a single column but two columns with the
> local and domain part
I couldn't find anything myself even after skimming through the code so I 
created PostgreSQL rules to circumvent the problem. Here they are in case 
anyone has the same problem. 

This is the view I created for listing shared folders:

CREATE VIEW view_shared_mailboxes AS
    SELECT shared_mailbox_local || '@' || shared_mailbox_domain AS 
"shared_mailbox", shared_to_local || '@' || shared_to_domain
AS "shared_to", 1
AS "dummy"
        FROM shared_mailboxes;

And these are the rules to enable INSERTSs and DELETEs:

CREATE RULE view_shared_mailboxes_insert AS ON INSERT TO view_shared_mailboxes
  DO INSTEAD
  INSERT INTO shared_mailboxes (shared_mailbox_local, shared_mailbox_domain, 
shared_to_local, shared_to_domain)
  VALUES (split_part(NEW.shared_mailbox,'@',1), 
split_part(NEW.shared_mailbox,'@',2),
split_part(NEW.shared_to,'@',1),
split_part(NEW.shared_to,'@',2));

CREATE RULE view_shared_mailboxes_delete AS ON DELETE TO view_shared_mailboxes
  DO INSTEAD
  DELETE FROM shared_mailboxes
  WHERE shared_mailbox_local = split_part(OLD.shared_mailbox,'@',1) AND
	shared_mailbox_domain = split_part(OLD.shared_mailbox,'@',2) AND
	shared_to_local = split_part(OLD.shared_to,'@',1) AND
	shared_to_domain = split_part(OLD.shared_to,'@',2);