You can now mark attributes in MK as "isIndexed" and the resulting SQL
column will get an index. This is important for the obj back refs that
are used for lists, so that retrieving lists is quick. You might have
other fields you wish to index like User.login (which would get
searched when someone attempts to log in to your site).
Regarding the specification in the object model: As usual, you can have
an "isIndexed" column which you fill out with 1s where needed (the
default is 0), or you can put "isIndexed=1" in the Extras column (which
is what I do cuz I have enough columns as it is).
On a related note, I've made MK fetches over twice as fast.
If you update from CVS you will have to "generate" again, of course.