title: How to export partial Cassandra table data to another Cassandra db?
body: <p>I have a special request that I have to export partial table's data to another Cassandra db. Two servers are in different data center in different country.</p>
  
  <p>The exported table is the same structure as original, only the new db is the subset of the old one.</p>
  
  <p>For example, the table has 3 column [user, cxtId, cxt], and the [user, cxtId] is the primary key.</p>
  
  <p>In general case, I will have a user with many cxtId. Assume I have ten user's data in db now, but I only want to export 3 of them into the new db, the target may has some data with the same primary key exist and I want overwrite that data.</p>
  
  <p>How can I do this in Cassandra.</p>
  
  <p>I have checked the COPY command, but it seems support full data set ( may with partial columns).</p>
  
  <p>Are there good approach to achieve my problem? Thank you.</p>
  
  <p>Eric </p>