[Dovecot] SIS for maildir?

[Timo Sirainen]

On Fri, 2010-09-03 at 12:07 -0500, Mike Abbott wrote:
> When might deduplication of attachments work with maildir?

I was planning on never. :) But here's a quick design idea:

 - Save normal mail data without attachments, similar to dbox
 - In maildir filename keep S= and W= the same as if the attachments
were there, just like with zlib plugin

Then one of:

a) Among cur/ new/ tmp/ directories create meta/ directory that contains
maildir metadata files. Each file has the same base filename as in cur/
directory. Contents could be similar to dbox metadata, most importantly
the attachment metadata.

b) Trust that dovecot-uidlist won't get deleted/corrupted and put the
attachment metadata into it.

c) Combine a+b so that b) is used but when something goes wrong it
fallbacks to reloading metadata from a). Still more disk I/O when
saving/deleting mails because of the creation/deletion of the metadata
file.

Possibly also something else is missing that I can't think of right now.

Hmm. This reminds me, it might be nice to be able to copy messages with
attachments in sdbox without temporarily duplicating the attachment..