Quoth Dmitry Kurochkin on Nov 08 at  8:34 am:
> Hi Austin.
> 
> On Mon,  7 Nov 2011 22:55:23 -0500, Austin Clements <amdragon@MIT.EDU> wrote:
> > This optimizes the user's tagging query to exclude messages that won't
> > be affected by the tagging operation, saving computation and IO for
> > redundant tagging operations.
> > 
> > For example,
> >   notmuch tag +notmuch to:notmuch@notmuchmail.org
> > will now use the query
> >   ( to:notmuch@notmuchmail.org ) and (not tag:"notmuch")
> > 
> > In the past, we've often suggested that people do this exact
> > transformation by hand for slow tagging operations.  This makes that
> > unnecessary.
> 
> Thanks!  This is a very useful optimization.
> 
> Does it work for multiple tags and tag removal?  I.e.:
> 
>   notmuch tag -inbox -unread +sent from:dmitry.kurochkin@gmail.com
> 
> can be converted to:
> 
>   notmuch tag -inbox -unread +sent from:dmitry.kurochkin@gmail.com and (tag:inbox or tag:unread or (not tag:sent))

Yep.  This is pretty much exactly what it does.