[Thomas Schwinge]
> +    /* This used to use NOTMUCH_SORT_MESSAGE_ID.  On 2011-10-29, a measurement
> +     * on a 372981 messages instance showed that wall time can be reduced from
> +     * 28 minutes (sorted by Message-ID) to 15 minutes (unsorted), the latter
> +     * being much more ``database-disk-layout-friendly''.  Subsequently sorting
> +     * the 25 MiB of data is a no-brainer, if required.  */

This sound like a great idea for my use case.  Doing 'notmuch dump'
with my 1.2 million emails take hours at the moment (not very fast
encrypted file system), and result in a 90 MiB dump file.
-- 
Happy hacking
Petter Reinholdtsen