public void unsetMatchColumn(int columnIdx) throws SQLException {
        // check if we are unsetting the SAME column
        if(! iMatchColumns.get(0).equals(Integer.valueOf(columnIdx) )  ) {
            throw new SQLException(resBundle.handleGetObject("jdbcrowsetimpl.unsetmatch").toString());
        } else if(strMatchColumns.get(0) != null) {
            throw new SQLException(resBundle.handleGetObject("jdbcrowsetimpl.usecolname").toString());
        } else {
                // that is, we are unsetting it.
               iMatchColumns.set(0, Integer.valueOf(-1));
        }
    }
Unsets the designated parameter to the given <code>int</code>
object.  This was set using <code>setMatchColumn</code>
as the column which will form the basis of the join.
<P>
The parameter value unset by this method should be same
as was set.

@param columnIdx the index into this rowset
       object's internal representation of parameter values
@throws SQLException if an error occurs or the
 parameter index is out of bounds or if the columnIdx is
 not the same as set using <code>setMatchColumn(int)</code>
src/main/java/org/replicadb/rowset/sun/rowset/JdbcRowSetImpl.java