sql-statements: flashback cluster support through ddl history (pingca…

…p#12811)

* sql-statements: flashback cluster support through ddl history

* Update sql-statement-flashback-to-timestamp.md

* Update sql-statement-flashback-to-timestamp.md

* Update sql-statements/sql-statement-flashback-to-timestamp.md

Co-authored-by: Ran <huangran.alex@gmail.com>

* Update sql-statements/sql-statement-flashback-to-timestamp.md

Co-authored-by: Ran <huangran.alex@gmail.com>

* Update sql-statements/sql-statement-flashback-to-timestamp.md

Co-authored-by: Ran <huangran.alex@gmail.com>

* Update sql-statement-flashback-to-timestamp.md

* Update sql-statements/sql-statement-flashback-to-timestamp.md

* Update sql-statements/sql-statement-flashback-to-timestamp.md

* Update sql-statements/sql-statement-flashback-to-timestamp.md

* Update sql-statements/sql-statement-flashback-to-timestamp.md

* Update sql-statements/sql-statement-flashback-to-timestamp.md

---------

Co-authored-by: Ran <huangran.alex@gmail.com>

sql-statements/sql-statement-flashback-to-timestamp.md

@@ -33,9 +33,11 @@ FlashbackToTimestampStmt ::=
     ```
 
 * 执行 `FLASHBACK CLUSTER` SQL 语句的用户需要有 `SUPER` 权限。
-* 在 `FLASHBACK` 指定的时间点到开始执行的时间段内不能存在相关表结构变更的 DDL 记录。若存在，TiDB 会拒绝该 DDL 操作。
-* 在执行 `FLASHBACK CLUSTER TO TIMESTAMP` 前，TiDB 会主动断开所有相关表上的连接，并禁止对这些表进行读写操作，直到 `FLASHBACK` 完成。
+* `FLASHBACK CLUSTER` 不支持回退修改 PD 相关信息的 DDL，如 `ALTER TABLE ATTRIBUTE`、`ALTER TABLE REPLICA`、`CREATE PLACEMENT POLICY` 等。
+* `FLASHBACK CLUSTER` 指定的时间点不能存在未执行完成的 DDL 记录。若存在，TiDB 会拒绝该 DDL 操作。
+* 在执行 `FLASHBACK CLUSTER TO TIMESTAMP` 前，TiDB 会主动断开所有相关表上的连接，并禁止对这些表进行读写操作，直到 `FLASHBACK CLUSTER` 完成。
 * `FLASHBACK CLUSTER TO TIMESTAMP` 命令不能取消，一旦开始执行 TiDB 会一直重试，直到成功。
+* 若 `FLASHBACK CLUSTER` 导致了元信息（表结构、库结构）的回滚，则相关的修改**不会**被 TiCDC 同步。因此，用户需主动暂停任务，待 `FLASHBACK CLUSTER` 完成后将上下游的 schema 定义手动同步一致，然后重新创建 TiCDC changefeed。
 
 ## 示例
 
@@ -74,22 +76,22 @@ mysql> SELECT * FROM t;
 Empty set (0.00 sec)
 ```
 
-如果从 `FLASHBACK` 指定的时间点到开始执行的时间段内有改变表结构的 DDL 记录，那么将执行失败：
+如果 `FLASHBACK CLUSTER` 指定的时间点有未完成的 DDL 记录，那么 `FLASHBACK CLUSTER` 将执行失败：
 
 ```sql
-mysql> SELECT now();
-+---------------------+
-| now()               |
-+---------------------+
-| 2022-10-09 16:40:51 |
-+---------------------+
-1 row in set (0.01 sec)
-
-mysql> CREATE TABLE t(a int);
-Query OK, 0 rows affected (0.12 sec)
-
-mysql> FLASHBACK CLUSTER TO TIMESTAMP '2022-10-09 16:40:51';
-ERROR 1105 (HY000): Detected schema change due to another DDL job during [2022-10-09 16:40:51 +0800 CST, now), can't do flashback
+mysql> ALTER TABLE t ADD INDEX k(a);
+Query OK, 0 rows affected (0.56 sec)
+
+mysql> ADMIN SHOW DDL JOBS 1;
++--------+---------+-----------------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+
+| JOB_ID | DB_NAME | TABLE_NAME            | JOB_TYPE               | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME         | START_TIME          | END_TIME            | STATE  |
++--------+---------+-----------------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+
+|     84 | test    | t                     | add index /* ingest */ | public       |         2 |       82 |         0 | 2023-01-29 14:33:11 | 2023-01-29 14:33:11 | 2023-01-29 14:33:12 | synced |
++--------+---------+-----------------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+
+1 rows in set (0.01 sec)
+
+mysql> FLASHBACK CLUSTER TO TIMESTAMP '2023-01-29 14:33:12';
+ERROR 1105 (HY000): Detected another DDL job at 2023-01-29 14:33:12 +0800 CST, can't do flashback
 ```
 
 可以通过日志查看 `FLASHBACK` 执行进度，具体的日志如下所示：