private static List<Integer> getChannelsForSymbols(
      List<Symbol> symbols, Map<Symbol, Integer> layout) {
    ImmutableList.Builder<Integer> builder = ImmutableList.builder();
    for (Symbol symbol : symbols) {
      builder.add(layout.get(symbol));
    }
    return builder.build();
  }
This Visitor is responsible for transferring Table PlanNode Tree to Table Operator Tree.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/TableOperatorGenerator.java