public int findColumn(String columnName) throws SQLException {
        checkState();

        return rs.findColumn(columnName);
    }
Maps the given <code>JdbcRowSetImpl</code> column name to its
<code>JdbcRowSetImpl</code> column index and reflects this on
the internal <code>ResultSet</code> object.

@param columnName the name of the column
@return the column index of the given column name
@throws SQLException if (1) a database access error occurs
(2) this rowset does not have a currently valid connection,
prepared statement, and result set
src/main/java/org/replicadb/rowset/sun/rowset/JdbcRowSetImpl.java