### _Why are the changes needed?_
This is required by Batch V2, as it allows the batch job queued in metastore before being picked by Kyuubi Server for scheduling.
### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [x] Add screenshots for manual tests if appropriate
```
mysql> CREATE TABLE IF NOT EXISTS metadata(
-> key_id bigint PRIMARY KEY AUTO_INCREMENT COMMENT 'the auto increment key id',
-> identifier varchar(36) NOT NULL COMMENT 'the identifier id, which is an UUID',
-> session_type varchar(32) NOT NULL COMMENT 'the session type, SQL or BATCH',
-> real_user varchar(255) NOT NULL COMMENT 'the real user',
-> user_name varchar(255) NOT NULL COMMENT 'the user name, might be a proxy user',
-> ip_address varchar(128) COMMENT 'the client ip address',
-> kyuubi_instance varchar(1024) NOT NULL COMMENT 'the kyuubi instance that creates this',
-> state varchar(128) NOT NULL COMMENT 'the session state',
-> resource varchar(1024) COMMENT 'the main resource',
-> class_name varchar(1024) COMMENT 'the main class name',
-> request_name varchar(1024) COMMENT 'the request name',
-> request_conf mediumtext COMMENT 'the request config map',
-> request_args mediumtext COMMENT 'the request arguments',
-> create_time BIGINT NOT NULL COMMENT 'the metadata create time',
-> engine_type varchar(32) NOT NULL COMMENT 'the engine type',
-> cluster_manager varchar(128) COMMENT 'the engine cluster manager',
-> engine_open_time bigint COMMENT 'the engine open time',
-> engine_id varchar(128) COMMENT 'the engine application id',
-> engine_name mediumtext COMMENT 'the engine application name',
-> engine_url varchar(1024) COMMENT 'the engine tracking url',
-> engine_state varchar(32) COMMENT 'the engine application state',
-> engine_error mediumtext COMMENT 'the engine application diagnose',
-> end_time bigint COMMENT 'the metadata end time',
-> peer_instance_closed boolean default '0' COMMENT 'closed by peer kyuubi instance',
-> UNIQUE INDEX unique_identifier_index(identifier),
-> INDEX user_name_index(user_name),
-> INDEX engine_type_index(engine_type)
-> ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
Query OK, 0 rows affected (0.04 sec)
mysql> ALTER TABLE metadata MODIFY kyuubi_instance varchar(1024) COMMENT 'the kyuubi instance that creates this';
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW CREATE TABLE metadata;
mysql> SHOW CREATE TABLE metadata;
+----------+---------------------------------------------------------------------------+
| Table | Create Table |
+----------+---------------------------------------------------------------------------+
| metadata | CREATE TABLE `metadata` (
`key_id` bigint NOT NULL AUTO_INCREMENT COMMENT 'the auto increment key id',
`identifier` varchar(36) NOT NULL COMMENT 'the identifier id, which is an UUID',
`session_type` varchar(32) NOT NULL COMMENT 'the session type, SQL or BATCH',
`real_user` varchar(255) NOT NULL COMMENT 'the real user',
`user_name` varchar(255) NOT NULL COMMENT 'the user name, might be a proxy user',
`ip_address` varchar(128) DEFAULT NULL COMMENT 'the client ip address',
`kyuubi_instance` varchar(1024) DEFAULT NULL COMMENT 'the kyuubi instance that creates this',
`state` varchar(128) NOT NULL COMMENT 'the session state',
`resource` varchar(1024) DEFAULT NULL COMMENT 'the main resource',
`class_name` varchar(1024) DEFAULT NULL COMMENT 'the main class name',
`request_name` varchar(1024) DEFAULT NULL COMMENT 'the request name',
`request_conf` mediumtext COMMENT 'the request config map',
`request_args` mediumtext COMMENT 'the request arguments',
`create_time` bigint NOT NULL COMMENT 'the metadata create time',
`engine_type` varchar(32) NOT NULL COMMENT 'the engine type',
`cluster_manager` varchar(128) DEFAULT NULL COMMENT 'the engine cluster manager',
`engine_open_time` bigint DEFAULT NULL COMMENT 'the engine open time',
`engine_id` varchar(128) DEFAULT NULL COMMENT 'the engine application id',
`engine_name` mediumtext COMMENT 'the engine application name',
`engine_url` varchar(1024) DEFAULT NULL COMMENT 'the engine tracking url',
`engine_state` varchar(32) DEFAULT NULL COMMENT 'the engine application state',
`engine_error` mediumtext COMMENT 'the engine application diagnose',
`end_time` bigint DEFAULT NULL COMMENT 'the metadata end time',
`peer_instance_closed` tinyint(1) DEFAULT '0' COMMENT 'closed by peer kyuubi instance',
PRIMARY KEY (`key_id`),
UNIQUE KEY `unique_identifier_index` (`identifier`),
KEY `user_name_index` (`user_name`),
KEY `engine_type_index` (`engine_type`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+----------+---------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
```
The derby SQL also is tested
<img width="1330" alt="image" src="https://github.com/apache/kyuubi/assets/26535726/4eef0742-05dd-4bd6-a77e-e9de0238375e">
- [ ] [Run test](https://kyuubi.readthedocs.io/en/master/contributing/code/testing.html#running-tests) locally before make a pull request
Closes#5078 from pan3793/nullable.
Closes#5078
0c5dec85d [Cheng Pan] Make kyuubi_instance nullable in metadata table schema
Authored-by: Cheng Pan <chengpan@apache.org>
Signed-off-by: Cheng Pan <chengpan@apache.org>
b1865fffa6