if (optimizeMultiGroupBy) {
curr = createCommonReduceSink(qb, input);
RowResolver currRR = opParseCtx.get(curr).getRR();
// create a forward operator
input = putOpInsertMap(OperatorFactory.getAndMakeChild(new forwardDesc(),
new RowSchema(currRR.getColumnInfos()), curr), currRR);
for (String dest : ks) {
curr = input;
curr = genGroupByPlan2MRMultiGroupBy(dest, qb, curr);