title: Cassandra batch select and batch update
body: <p>I have a requirement to update all users with a specific value in a job.</p>
  
  <p>i have million of users in my Cassandra database. is it okay to query million user first and do some kind of batch update? or is there some implementation available to do these kind of work. I am using hector API to interact with Cassandra. What can be the best possible way to do this.?</p>