public static void serialize(Expression expression, DataOutputStream stream) throws IOException {
    ReadWriteIOUtils.write(expression.getExpressionType().getExpressionTypeInShortEnum(), stream);
    expression.serialize(stream);
  }
Accessible for {@link AstVisitor}, use {@link AstVisitor#process(Node, Object)} instead.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/Expression.java