I'm aiming to get Xapian 1.2 into the next Debian stable release, so I
am in the process of checking all the Debian packages which depend on
Xapian, one of which is roundup.

Xapian 1.2.0 drops support for some deprecated features, and roundup
uses one: MSetItem's get_docid() method should now be a docid property.
 This change is compatible with 1.0.x as well, but may not be with
0.9.x.  But Xapian 0.9.x is completely obsolete now so I just update the
install docs to give 1.0.0 as the minimum requirement.

Also, transactions have been supported for ages (since 0.9.7) so I
enabled those.

And MSet now implements __len__ so I made that change.

I'll attach a patch with these changes, but I'm afraid it is untested as
I don't actually use roundup, and I could see any unit tests which
covered this.  I hope it's useful as a pointer though.  If you need help
or advice on Xapian, feel free to ask.