title: Querying Cassandra by a partial partition key
body: <p>In Cassandra, I can create a composite partition key, separate from my clustering key:</p>
  
  <pre><code>CREATE TABLE footable (
      column1 text,
      column2 text,
      column3 text,
      column4 text,
      PRIMARY KEY ((column1, column2))
  )
  </code></pre>
  
  <p>As I understand it, quering by partition key is an extremely efficient (the most efficient?) method for retrieving data. What I don't know, however, is whether it's also efficient to query by only part of a composite partition key.</p>
  
  <p>In MSSQL, this would be efficient, as long as components are included starting with the first (column1 instead of column2, in this example). Is this also the case in Cassandra? Is it highly efficient to query for rows based only on column1, here?</p>