Re: Why article numbers?

[kai.grossjohann@uni-duisburg.de (Kai Großjohann)]

Simon Josefsson <jas@extundo.com> writes:

> kai.grossjohann@uni-duisburg.de (Kai Großjohann) writes:
>
>> Simon Josefsson <jas@extundo.com> writes:
>>
>>> Regarding the nnimap issue, a better solution would IMHO be to fix it
>>> to do proper re-syncing on UIDVALIDITY changes, which it probably
>>> would have to do even if message-id's are used to index articles since
>>> IMAP uses integers to retrieve articles anyway.
>>
>> Is this possible?
>
> To fix it?  The situation is detected now (but ignored).  What would
> be required to make it work, would be to wipe out the gnus info for
> that group and replace it with new data from the server.  If the agent
> is used, the NOV cache and .agentview and cached articles must be
> removed too.  As for cached articles, I'm not sure to handle them --
> removing locally cached articles might be a bad idea since the user
> might want to keep them.  Gnus-specific flags (i.e., bookmarks) simply
> would have to be dropped unless some more information (like
> message-id) about the marked articles were available to search for its
> new article number.  It is a lot of work, and no backend interface to
> do it so nnimap would have to contain even more Gnus internal
> knowledge.  Fortunately, people rarely send bug reports about this (I
> can rememeber <5 times this was the real cause of a problem) so either
> it isn't that important or people give up Gnus for some other client
> and doesn't tell us.

Yeah.  What I think should happen is a renumbering.  For the cache,
renumbering is actually easier, most of the time: just renumber the
cached articles to start at 1, and you'll be fine in most cases.

The copies in the agent are a thornier issue.  I think it would not
be good to just delete them: they will then be fetched again from the
server, which is a waste of bandwidth that we wanted to avoid by
using the agent in the first place...

If you have an index of the local copies by message id, then you
could just ask the server for the headers (NOV) and then search for
articles mentioned there by message id.  That tells you which number
to use locally, and then there could be some articles that aren't
found on the server -- we want to delete them I think.

Hm.

Maybe the cache should be treated a little bit like a separate
backend, kind of like nnvirtual does it, at least conceptually.  I
think it would be best to just decouple the numbers used in the cache
totally from the numbers used on the server.  This leads to problems
when the cached articles are still on the server, but oh, well.

For the agent, the renumbering approach appears to be best.  (`Lost'
articles could be moved from the agent to the cache instead of
deleting them, now that I think about it.)

-- 
A preposition is not a good thing to end a sentence with.