执行json_object，结果返回字段顺序会改变，和mariadb，mysql数据库不一样

[co63oc]

mysql> SELECT JSON_OBJECT('id', 123, 'name', 'polardb-x');
+---------------------------------------------+
| JSON_OBJECT('id', 123, 'name', 'polardb-x') |
+---------------------------------------------+
| {"name":"polardb-x","id":123} |
+---------------------------------------------+
1 row in set (0.00 sec)

mariadb数据库的结果为，这应该是和mysql数据库一样
MariaDB [(none)]> SELECT JSON_OBJECT('id', 123, 'name', 'polardb-x');
+---------------------------------------------+
| JSON_OBJECT('id', 123, 'name', 'polardb-x') |
+---------------------------------------------+
| {"id": 123, "name": "polardb-x"} |
+---------------------------------------------+
1 row in set (0.000 sec)

[co63oc]

mysqld测试结果
mysql> SELECT JSON_OBJECT('id', 123, 'name', 'polardb-x');
+---------------------------------------------+
| JSON_OBJECT('id', 123, 'name', 'polardb-x') |
+---------------------------------------------+
| {"id": 123, "name": "polardb-x"} |
+---------------------------------------------+
1 row in set (0.00 sec)

[co63oc]

polardbx-optimizer\src\main\java\com\alibaba\polardbx\optimizer\core\function\calc\scalar\json\JsonObject.java
对应源码，生fastjson成json时会有顺序，没找到怎么改变设置顺序

    @Override
    public Object compute(Object[] args, ExecutionContext ec) {
        if (args.length % 2 != 0) {
            throw JsonParserException.wrongParamCount(getFunctionNames()[0]);
        }

        Map<String, Object> resultJson = Maps.newHashMap();
        for (int i = 0; i < args.length; i += 2) {
            if (args[i] == null) {
                throw new JsonParserException("JSON documents may not contain NULL member names.");
            }

            if (i + 1 < args.length) {
                resultJson.put(DataTypeUtil.convert(operandTypes.get(i), DataTypes.StringType, args[i]), args[i + 1]);
            } else {
                throw JsonParserException.wrongParamCount(getFunctionNames()[0]);
            }
        }

        return JSON.toJSONString(resultJson);
    }

[F-ca7]

关于MySQL 对 json_object输出顺序的描述：https://dev.mysql.com/doc/refman/8.0/en/json.html#json-normalization

To make lookups more efficient, MySQL also sorts the keys of a JSON object. You should be aware that the result of this ordering is subject to change and not guaranteed to be consistent across releases.

MySQL会对 JSON对象的key进行排序，但是不保证这个顺序在每个发行版都是一致的。

而PolarDB-X中调用了FastJson的接口，底层com.alibaba.fastjson.serializer.MapSerializer 是基于HashMap的遍历，这个同样也是不保证顺序的。