Re: Backend writing

[Simon Josefsson <jas@extundo.com>]

Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) writes:

>> Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) writes:
>> 
>>>| that number, or Gnus will get mightily confused.@footnote{??? Is
>>>| this still true with the nnchoke-request-*-mark* functions?}
>>>| Third, article
>> 
>> It's still true.
> 
> But haven't you just changed nnimap to ignore article renumberings?  I
> suppose you wouldn't do that unless it's safe?

I don't know if it's safe, that's what Oort is for. <g>

Basicly, nnimap makes sure the old NOV cache isn't used when a
uidvalidity has changed.  Nnimap also updates all Gnus marks when
entering a group so they should be OK.  The only thing left is the
active range, and that's updated by Gnus when you `g', `M-g' or
somesuch.  Possibly a uidvalidity change breaks the cache or the agent
if article numbers are actually re-used.  But in several cases IMAP
servers update UIDVALIDITY but still does not re-use article numbers,
so in those cases it's OK to ignore the error.

It gets sort of ugly if a backend has to update internal things of
Gnus's cache and agent.  Some sort of mechanism to handle renumberings
in the cache and agent would be nice.

>>>| The previous paragraph already mentions all the `hard'
>>>| restrictions that article numbers must fulfill.  But it seems that
>>>| it might be useful to assign @emph{consecutive} article numbers,
>>>| for Gnus gets quite confused if there are holes in the article
>>>| numbering sequence.  However, due to the `no-reuse' restriction,
>>>| holes cannot be avoided altogether.
>> 
>> I would say "is slowed down" instead of "gets quite confused".  I
>> don't think there are any problems, other than that the
>> `gnus-range-*' functions start to take very long time.  Some IMAP
>> servers leave large holes.
> 
> I meant that Gnus says `1276423 messages in this group, how many?' or
> something like that when the user enters the group.

That's another side-effect of the high/low article number story.  It's
documented, so maybe we could call it a feature.  For now at least.