[Dovecot] Compressing existing maildirs

[Jan-Frode Myklebust]

On Thu, Dec 29, 2011 at 03:48:05PM +0200, Timo Sirainen wrote:
> > 
> > Can't I trust that no mails with timestamp before I enabled compression
> > are uncompressed? Or will dovecot compress old messages keeping old
> > timestamp when copying messages between folders, or something like that?
> 
> It's possible that a user saves a mail with an old IMAP INTERNALDATE (=file's mtime), which is already compressed. You could use ctime, but that could skip mails whose flags have been changed since compression.

Ok, if ctime is safer I think I'll use that and not worry too much about
missing some messages.

> 
> > I want to avoid reading every file to check if it's compressed
> > already, as that will add ages to an already slow process..
> 
> You could use mtime, and just before compressing the mail check if it's already compressed. That won't add much overhead.

Ah, right.. I'll have to read the messages from disk anyway, so checking
if they're compressed or not doesn't add much. So mtime +
compression-check is what I'll need to do then.


  -jf