it's common in SQL and JDBC API to return count of affected rows.
Hive should do the same (it's not as of 9/24/2014)
Hive JDBC driver should return a proper update-count of rows affected by query
Advance Hadoop Architecture (AHA) - Advance Hive (Umbrella) JIRA -- Enhanced Updates & others
Implement insert, update, and delete in Hive with full ACID support