I've backported the term update optimisation patches <http://trac.xapian.org/ticket/250> to Xapian's 1.0 branch, and you can find snapshot tarballs including these changes here: http://oligarchy.co.uk/xapian/branches/1.0/ Xapian's testsuite passes (including the additional test coverage which I also backported), and I looked over each change carefully, but I would be interested to see some real world testing, particularly in the situation which these changes are intended to improve (i.e. speed of tagging in notmuch). So if you're so inclined, try it and report how you got on (on this list is fine). Cheers, Olly