outputMappings.put(symbol, new Input(channel, 0)); // one column per channel
channel++;
}
List<TupleInfo> tupleInfos = getSourceOperatorTupleInfos(node, context.getTypes());
OperatorFactory operatorFactory = new TableScanOperatorFactory(context.getNextOperatorId(), node.getId(), dataStreamProvider, tupleInfos, columns);
return new PhysicalOperation(operatorFactory, outputMappings.build());
}