dovecot - May 2010 - mdbox: Is there any more info on the "cleanup" step? (Dovecot 2.0beta5)

The wiki page which mentions mdbox talks about a "cleanup" step for
mdbox:

: The space is later freed in "cleanup" step. This may be done
: automatically within the session or later in a nightly cronjob when
: there's less disk I/O. The cleanup first finds all files that have
: refcount=0 mails. Then it goes through each file and copies the
: refcount>0 mails to other dbox files (to the same files as where newly
: saved messages would also go), updates the map index and finally
: deletes the original file. So there is never any overwriting or file
: truncation.

I was wondering if there was any code to actually do this, or any 
command-line tools (and if either of those where they might be), or 
whether it was just design musings at the minute.

Regards,

Bill

On Thu, 2010-05-13 at 10:33 +0100, William Blunn wrote:
> The wiki page which mentions mdbox talks about a "cleanup" step
for mdbox:
> 
> : The space is later freed in "cleanup" step. This may be done
> : automatically within the session or later in a nightly cronjob when
> : there's less disk I/O. The cleanup first finds all files that have
> : refcount=0 mails. Then it goes through each file and copies the
> : refcount>0 mails to other dbox files (to the same files as where newly
> : saved messages would also go), updates the map index and finally
> : deletes the original file. So there is never any overwriting or file
> : truncation.
> 
> I was wondering if there was any code to actually do this, or any 
> command-line tools (and if either of those where they might be), or 
> whether it was just design musings at the minute.
doveadm purge does this step. There were also some plans to do it
automatically sometimes, but this doesn't happen currently.