[Dovecot] dovecot.index is missing

[Timo Sirainen]

On Tue, 2013-01-29 at 03:37 -0600, Stan Hoeppner wrote:
> On 1/29/2013 1:37 AM, Alexandr Sabitov wrote:
> > Dear All,
> > 
> > I have noticed that dovecot.index is not generated straight away if you have just a few emails in the mailbox. Instead of that dovecot.index.log is modified and accessed by clients.
> > 
> > Only if the number of email reaches some level then it creates dovecot.index in user mailboxes.
> > 
> > Can somebody please tell me when (in my understanding of the process) the index log file drops all data into the mail index file. What does trigger that ?
> > Sorry I couldn't find any info on that in the wiki.
> 
> Dovecot is behaving here as designed.   You haven't found the technical
> answer because there is no configurable variable for this behavior--it's
> hard coded.  Thus it is not documented.
> 
> The layman's explanation is this:  up to a certain amount of mail it is
> more expensive to create the index than to simply read the mail.  Beyond
> that point indexing has benefit.  To understand how that decision is
> made requires reading the source, and understanding it.

The index still exists. It's just that for new mailboxes the
dovecot.index.log file contains everything that is necessary to create a
dovecot.index file, and Dovecot just hasn't gotten around to actually
creating it. If a mailbox shrinks enough, the dovecot.index file could
in theory be deleted as well (and maybe in future Dovecot version it
will).

So dovecot.index is just a snapshot that gets updated every once in a
while. http://wiki2.dovecot.org/IndexFiles and
http://wiki2.dovecot.org/Design/Indexes has some more details, although
they don't seem to talk about this exact thing.