title: what's the best way to re-index just the models that changed during solr downtime?
body: <p>if I have millions of User records with some text fields getting indexed to solr on create and on update, how do I go back and re-index the few records that never made it to solr?</p>
  
  <p>i.e. what if solr goes down for a few minutes during the day and about 300 records out of millions never got indexed.</p>
  
  <p>I don't want to re-index millions of records, just the 300.</p>