We need both the entries that don't pass the specified filter for the
attribute, and those that don't have the attribute at all. We would
need a way to get all entries that are not contained in the index for
the attribute and a way to join that enumeration to the one we had in
the old code (which should be easy enough with a JoinedEnumeration class).
I think the current attribute indices need to be modified to store a
list of entries that do not have the attribute. Each index will then
take up a bit more space.
All existing ApacheDS installations would
also need their attribute indices rebuilding too.
What do you think?