@Override
  public ColumnTransformer visitExpression(
      Expression expression, ColumnTransformerVisitorContext context) {
    throw new UnsupportedOperationException(
        "Unsupported statement type: " + expression.getClass().getName());
  }
Responsible for constructing {@link ColumnTransformer} through Expression.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/expression/visitor/ColumnTransformerVisitor.java