private boolean generateIdentityColumnTransformerIfPossible(
      Expression expression, ColumnTransformerVisitorContext context) {
    List<InputLocation> inputLocations =
        context.inputLocations.get(expression.getExpressionString());
    if (inputLocations != null) {
      IdentityColumnTransformer identity =
          new IdentityColumnTransformer(
              TypeFactory.getType(context.getType(expression)),
              inputLocations.get(0).getValueColumnIndex());
      // add to leafList
      context.leafList.add(identity);
      context.cache.put(expression, identity);
      return true;
    }
    return false;
  }
the input could be calculated expressions that we can use directly and we do not need to do
further calculation if so

@return true if the expression has been calculated
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/expression/visitor/ColumnTransformerVisitor.java