[RFC PATCH 00/14] modular mail stores based on URIs

[Ethan]

I sent this at first as a reply-only-to-sender. Oops! Sorry Mark for the
double send.

On Wed, Jun 27, 2012 at 5:17 AM, Mark Walters <markwalters1009 at gmail.com>wrote:

> > Personally, this isn't my favorite approach, for the following reasons:
> >
> > 1. Notmuch, at some point in its history, chose to store file paths
> > relative to a "mail database", with the intent that if this mail
> > database was moved, filenames would not change and everything would
> > Just Work (tm). The above scheme completely reverses this design
> > decision, and in general completely breaks this relocatability. I
> > don't see any easy way to handle this problem. This isn't just a
> > wishlist feature; at least two things in the test suite (caching of
> > corpus.mail, and the atomicity tests) rely on this behavior.
>
> Why can't the URI just store a relative path, at least for maildir://
> and mbox:// ? It is purely internal to notmuch so it doesn't need to be
> very standard.
>

Well, relative to where? This is especially relevant now that we can have
multiple mail stores. It sounds like you are suggesting that all mbox://
URIs are relative to an "mbox root", but the fundamental question is how to
pass that information from the configuration into the library.

Even using configuration itself may be problematic, because only the CLI
uses the configuration, and language bindings like Python and Ruby might
get out of sync! (But note also that the Python bindings currently use
.notmuch-config to find the database path, so maybe it's not a big deal.)

If I could do whatever I wanted, every mailstore would get registered
somehow and the URIs could use those registered names to specify what
they're relative to: maybe using hostname, such as
maildir://university-mail/some-mail-file, mbox://old-unix-system/some.mbox.
Then changing these names in .notmuch-config would be fine. I just don't
know how to pass that configuration information without an approach like in
the past patch series.

 > 2. Mail access information, i.e. open connections, etc. can only be
> > stored in variables global to the mailstore code, and cannot be stored
> > as private members of a mailstore object. This is more an aesthetic
> > concern than a functional one.
> >
> > Anyhow, the following (enormous) patch series implement this design. I
> > used uriparser as an external library to parse URIs. The API for this
> > library is a little idiosyncratic. uriparser supports parsing Unicode
> > URIs (strings of wchar_t), but I just used ASCII filenames because I
> > think that's what comes out of Xapian.
>
> Why use a library? Isn't it just a question of does the string contain
> // and, if so, splitting it? I guess that // is a nice separator as I
> think we can assume that a true path does not contain it (since a
> filename cannot contain /).
>

The URIs are true URIs. Filenames are provided by the "path" segment of the
uri -- everything from the first slash after the hostname up to a ? for
query arguments. My concern was that filenames could (in theory) contain #
or ?, and in practice they contain : (maildir flags). I figured it was
better to do it right.

 > Patch 11 is borrowed directly from the last patch series.
> >
> > The last four or five patches add mbox support, including a few
> > tests. That part of the series is still very first-draft: I added a
> > new config option to specify URIs to scan, and ">From " lines still
> > need to be unescaped. However, we support scanning mbox files whether
> > messages have content-length or not.
>
> I have an idea that mbox byte-locations change when messages are marked
> as read (amongst other things). It might be worth saying that this
> initial implementation only works for unchanging mboxs (rather than the
> append only condition that you currently say). But I have not got as far
> as applying/testing the series yet.
>

Yeah, I don't even know how an mbox message gets flagged read and I don't
know how I would support it.

Ethan
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