Re: Registry.. what is its purpose?

[Ted Zlatanov <tzz@lifelogs.com>]

On Sat, 10 May 2003, hgp@sbcglobal.net wrote:
> Sorry for the dumb question but starting at the top of gnus info
> manual for 5.10.1 (Which is what came with my cvs 5.10.2) an `index'
> search doesn't hit `registry' neither does an `s' search.

It's far from stable, so I haven't put any info in the manual yet.

> Looking at posted messages about the registry, I find only bits and
> pieces, though I'm sure it was fully explained if taken together or
> maybe way back down the road some where.
> 
> I wondered if someone in the know about the registry could give an
> overview of its purpose in life.

That would be me.  The registry associates group names and extra data
with a Message-ID, not with an article number as the rest of Gnus
does.  It uses hooks to catch article delete, move, copy, etc.  You
can set a group/topic parameter of registry-ignore or the variable
gnus-registry-ignored-groups if you want to avoid registering
particular backends or group names.

The registry is saved as an alist in ~/.gnus.registry.eld currently.
I'm thinking of an optimized storage format, but Gnus and Emacs don't
have a fast file database that I know of.

It is currently only used for gnus-registry-split-fancy-with-parent,
which is analogous to nnmail-split-fancy-with-parent but it's useful
for generic backends (including nnimap, that is).  You just call it in
your split-fancy and it figures out what group the message belongs to,
using the References or In-Reply-To headers (the code was copied from
nnmail-split-fancy-with-parent).

The registry will be used for spam.el.  It will remember if a message
was registered with a spam or ham processor, and will be able to undo
that action or avoid doing it twice (for instance, if the same message
is marked as spam twice by accident, there's no need to process it as
spam twice and in fact that may be statistically undesirable).

Right now, there are some issues:

- the registry may need to be stored in a way that allows multiple
  machines to share it.  I think I will use IMAP storage (imap-db.el
  which I am developing) to store a generic file in an IMAP group.  If
  the registry is not shared between multiple machines, and one
  machine does article spooling, copies, moves, or deletions, the
  other machines will not know to update the article IDs' info in the
  registry.  Suggestions are welcome.

- only the short group name is saved, because I could not find a
  reliable way to get the long group name in every case.  This still
  works, but is not complete.

See the source in gnus-registry.el if you are interested in the
implementation.

Thanks
Ted