diff --git a/interface/cassandra.thrift b/interface/cassandra.thrift
index 1fc7201b64..4eda4f82a2 100644
--- a/interface/cassandra.thrift
+++ b/interface/cassandra.thrift
@@ -496,7 +496,14 @@ enum CqlResultType {
     INT = 3
 }
 
-/** Row returned from a CQL query */
+/** 
+  Row returned from a CQL query.
+
+  This struct is used for both CQL2 and CQL3 queries.  For CQL2, the partition key
+  is special-cased and is always returned.  For CQL3, it is not special cased;
+  it will be included in the columns list if it was included in the SELECT and
+  the key field is always null.
+*/
 struct CqlRow {
     1: required binary key,
     2: required list<Column> columns