for(int i = 0; i < groupFields.length(); i++) {
String groupByField = groupFields.getString(i);
int fieldIndex = query.getSelectFieldIndex(groupByField);
Assert.assertTrue(fieldIndex >= 0 && fieldIndex <selectFields.size(), "Impossible to group on field [" + groupByField + "]");
String[] f = (String[])selectFields.get(fieldIndex);
transformer.addGrouByColumn(f[1]!=null? f[1]:f[0], query.getSelectFieldByIndex(fieldIndex).getAlias());
}
// count column
transformer.addAggregateColumn("*"/*f[1]!=null? f[1]:f[0]*/, "COUNT", "Records");