title: SPARK Steaming updateStateByKey values from previous Microbatch when no new such data for current Microbatch
body: <p>It is unclear to me if I want to show the top N ocurrences over all Microbatches to-date for some key with simple counts, whether this is possible with standard Spark Streaming when not UNIONing or JOINing in an appropriate manner! with a saved / persisted set of data taking into account that current processing may not have keys to process that were in the top 5. </p>
  
  <p>I.e. If the top 5 for current processing of an initial Microbatch are x,y,z,a,b and, then if, say, the next Microbatch has x,c,m only as data, can I retrieve a, b and y and z as part of the top 5 if c and m have less occurrences than these priors in terms of top 5?  </p>
  
  <p>May be it is a bad Use Case.</p>