Quoth Jani Nikula on Nov 05 at 12:34 am:
> On Sat, 03 Nov 2012, David Bremner <david@tethera.net> wrote:
> > Eirik Byrkjeflot Anonsen <eirik@eirikba.org> writes:
> >
> >> That's not what I see.  If I search for a term that only appears in
> >> one of the "copies", none of the copies are included in the search
> >> result.
> >
> > The offending code is at line 1813 of lib/database.cc; the message is
> > only indexed if the message-id is new.
> >
> > It might be sensible to move _notmuch_message_index_file into the other
> > branch of the if, but even if that works fine, something more
> > sophisticated is needed for the call to
> > __notmuch_message_set_header_values; the invariant that each message has
> > a single subject seems reasonable.
> >
> > Offhand I'm not sure of a good method of automatically deciding what is
> > the same message (with e.g. headers and footer text added by a mailing
> > list).
> 
> Assuming there was good method, what would you do with two different
> messages that have the same message id? That is the unique id we use to
> identify messages (which should be fine per RFC 5322 and its
> predecessors; we're talking about messages from broken systems here).
> 
> It might be helpful to have a configuration option similar to new.tags
> that would define the tags to be assigned to messages with duplicate
> message ids. (This could be done in the
> NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID case near line 516 of
> notmuch-new.c). This could be used to assign a "dupe" tag, for example,
> so the user could do whatever they want in the post-new hook or the user
> interface. A sufficiently clever post-new hook could compare the files
> of a message, and drop the tag or add another, as the case may
> be. Surely not a perfect solution, but keeps the implementation simple.

This would also trigger on message flag changes and folder moves
performed outside of notmuch, since notmuch sees those as a duplicate
message ID followed by a deletion.  The only way to do something for
every received message even if it has the same message ID as an
existing message is to do it in whatever delivers mail.  Currently, we
don't have a good story for integrating on-delivery operations with
notmuch.