RowResolver outputRS = opParseCtxMap.get(op).getRowResolver();
MapJoinOperator mapJoinOp = (MapJoinOperator) OperatorFactory.getAndMakeChild(
mapJoinDescriptor, new RowSchema(outputRS.getColumnInfos()), op.getParentOperators());
OpParseContext ctx = new OpParseContext(outputRS);
opParseCtxMap.put(mapJoinOp, ctx);
mapJoinOp.getConf().setReversedExprs(op.getConf().getReversedExprs());
mapJoinOp.setColumnExprMap(colExprMap);