// ---- GROUP BY
if ( query.hasGroupBy() )
{
// When there is no GroupBy but there are some aggregates, it's a group of no variables.
op = new OpGroup(op, query.getGroupBy(), query.getAggregators()) ;
}
//---- Assignments from SELECT and other places (so available to ORDER and HAVING)
// Now do assignments from expressions
// Must be after "group by" has introduced it's variables.