GenMRProcContext ctx = (GenMRProcContext) opProcCtx;
// union consisted on a bunch of map-reduce jobs, and it has been split at
// the union
Operator<? extends OperatorDesc> reducer = op.getChildOperators().get(0);
UnionOperator union = Utils.findNode(stack, UnionOperator.class);
assert union != null;
Map<Operator<? extends OperatorDesc>, GenMapRedCtx> mapCurrCtx = ctx
.getMapCurrCtx();
GenMapRedCtx mapredCtx = mapCurrCtx.get(union);