public int[] getKeyColumns() throws SQLException {
      int[]keyColumns  = this.keyCols;
      return (keyColumns == null) ? null : Arrays.copyOf(keyColumns, keyColumns.length);
   }
Returns the columns that make a key to uniquely identify a
row in this <code>StreamingRowSetImpl</code> object.

@return an array of column numbers that constitutes a primary
          key for this rowset. This array should be empty
          if no column is representitive of a primary key
@throws SQLException if the rowset is empty or no columns
          are designated as primary keys
@see #setKeyColumns
src/main/java/org/replicadb/rowset/StreamingRowSetImpl.java