Re: Gnus maildir backend issues

[Paul Jarc]

Sascha Wilde <address@hidden> wrote:
> address@hidden (Paul Jarc) wrote:
>> [.nmaildir/num/ files are] used to keep track of article number
>> assignments.  If you remove them, you may cause some data
>> corruption.
>
> Hu?  I removed the entire .nnmaildir sometimes and had no problems.

It depends on what Gnus features you use.  Removing those files will
make nnmaildir reassign article numbers, which may be different from
the article numbers that were assigned the first time.  If you use any
features that store article numbers outside the backend, such as the
cache or agent, then you'll have trouble.

Also, deleting just some of the num/* files, and leaving the rest of
.nnmaildir intact, will definitely cause trouble, even for just
gathering new messages.

> Even more, I wouldn't expect to encounter an problems as I would expect
> the original maildir to be self contained.  Actually for most other MUAs
> it is, isn't it?

Could be; I'm not familiar with any others enough to say.  It's
certainly possible to design a MUA from scratch so that all metadata
can be regenerated at any time.  nnmaildir does that as much as it can
(removing the nov/* files is safe), but Gnus requires numeric IDs
assigned to articles, and some features require those IDs to never
change.  So deleting the information of what numbers have been
assigned will screw up those features.

> First of all I consider it problematic in general, to store meta
> data forever.  Why would one need any information on mails deleted
> years ago?

As much of the metadata as possible is deleted along with the article
itself.  All that is kept is the fact that the article number has
already been assigned, so it won't be reused.

> excluding all the .nnmaildir directories makes entering the commands
> more cumbersome.  Not a big issue, but annoying.

If I had to do that often, I'd make a small script or some other kind
of shortcut.


paul