title: DIH in SOLR based on primary key of a table
body: <p>currently am using DIH for pulling data from MSSQL server to SOLR. Where in am using dataimporter.last_index_time to pull the records which are into database only after last_index_time. So i was exploring if there are any other option for DIH to use instead of using last_index_time may be something like last_pk_id. 
  Is such option available?  could anyone let me know. </p>