title: Unique Key generation in Hive/Hadoop
body: <p>While selecting a set of records from a big data hive table, a unique key needs to be created for each record. In a sequential mode of operation , it is easy to generate unique id by calling soem thing like max(id). Since hive runs the task in parallel, how can we generate unique key as part of a select query, without compromising the performance of hadoop.
  Is this really a map reduce problem or do we need to go for a sequential approach to solve this.</p>