分类目录归档：MySQL

MySQL 8.0版本ibd文件恢复

发表于 2022 年 12 月 18 日 由 惜分飞

对于单个的ibd文件,大部分情况下可以通过DISCARD TABLESPACE和IMPORT TABLESPACE方式进行恢复

mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> CREATE TABLE `t1` (
    ->   `id` int DEFAULT NULL
    -> ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
Query OK, 0 rows affected (0.01 sec)
mysql> insert into t1 values(1);
Query OK, 1 row affected (0.02 sec)

mysql> insert into t1 values(2);
Query OK, 1 row affected (0.01 sec)

mysql> insert into t1 values(3);
Query OK, 1 row affected (0.00 sec)

关闭mysql服务，备份mysql中的t1.ibd文件

[root@xifenfei ~]# service mysql stop
Shutting down MySQL..... SUCCESS! 
[root@xifenfei test]# cp t1.ibd  t1_bak

启动mysql服务,并删除并创建新的t1表(表结构相同)

[root@xifenfei test]# service mysql start
Starting MySQL..................... SUCCESS! 


[root@xifenfei test]# mysql -uroot -poracle test
mysql: [Warning] Using a password on the command line interface can be insecure.
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.31 MySQL Community Server - GPL

Copyright (c) 2000, 2022, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> drop table t1;
Query OK, 0 rows affected (0.20 sec)


mysql> 
mysql> CREATE TABLE `t1` (
    ->   `id` int DEFAULT NULL
    -> ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
Query OK, 0 rows affected (0.01 sec)

DISCARD TABLESPACE操作

mysql> ALTER TABLE t1 DISCARD TABLESPACE;
Query OK, 0 rows affected (0.01 sec)

把备份的t1.ibd还原回去并修改权限

[root@xifenfei test]# mv t1_bak t1.ibd
[root@xifenfei test]# ls -ltr
total 112
-rw-r-----. 1 root root 114688 Dec 18 17:24 t1.ibd
[root@xifenfei test]# chown mysql.mysql t1.ibd

IMPORT TABLESPACE并验证数据

mysql> ALTER TABLE t1 IMPORT TABLESPACE;
Query OK, 0 rows affected, 1 warning (0.24 sec)

mysql> select * from t1;
+------+
| id   |
+------+
|    1 |
|    2 |
|    3 |
+------+
3 rows in set (0.00 sec)

在恢复途中如果遇到表定义不对,或者ibd文件损坏，或者版本不匹配等各种情况,可能在IMPORT TABLESPACE的时候可能出现类似ERROR 1808 (HY000): Schema mismatch (Clustered index validation failed. Because the .cfg file is missing, table definition of the IBD file could be different. Or the data file itself is already corrupted.)错误

mysql>  alter table       `t1` import tablespace;                    
ERROR 1808 (HY000): Schema mismatch (Clustered index validation failed. 
Because the .cfg file is missing, table definition of the IBD file could be different. 
Or the data file itself is already corrupted.)

如果出现此类错误,无法直接通过该方法进行解决,参考frm和ibd文件数据库恢复,使用专业恢复工具进行处理

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MyISAM表delete记录恢复

发表于 2022 年 11 月 25 日 由 惜分飞

有客户delete删除了myisam表中的部分数据,本来表中4-5w条记录,删除之后值剩余几十条,希望对其进行恢复（该库没有开启binlog）

mysql> select count(1) from db_bet;
+----------+
| count(1) |
+----------+
|       46 |
+----------+
1 row in set (0.00 sec)

通过分析.MYD文件确认数据依旧在文件中
myisam-delete-recovery

通过工具对其删除操作分析,找到记录如下
20221125175222
对其记录入库确认

mysql> select count(1) from db_bet_deleted;
+----------+
| count(1) |
+----------+
|    40158 |
+----------+
1 row in set (0.10 sec)
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修改MySQL的ib_logfile大小和组数

发表于 2022 年 7 月 16 日 由 惜分飞

在某些情况下，需要修改MySQL的ib_logfile大小和组数(类似oracle redo),以下演示在MySQL 8.0修改ib_logfile大小和组数操作
查看当前ib_logfile情况

mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.21    |
+-----------+
1 row in set (0.00 sec)

mysql> show variables like '%innodb_log_file%';
+---------------------------+-----------+
| Variable_name             | Value     |
+---------------------------+-----------+
| innodb_log_file_size      | 134217728 |
| innodb_log_files_in_group | 2         |
+---------------------------+-----------+
2 rows in set, 1 warning (0.00 sec)

mysql> show variables like '%innodb_log_group_home_dir%';
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| innodb_log_group_home_dir | .\    |
+---------------------------+-------+
1 row in set, 1 warning (0.00 sec)

mysql> show variables like '%datadir%';
+---------------+---------------+
| Variable_name | Value         |
+---------------+---------------+
| datadir       | E:\MySQL\8.0\ |
+---------------+---------------+
1 row in set, 1 warning (0.00 sec)

C:\Users\XFF>dir E:\MySQL\8.0\ib_log*
 驱动器 E 中的卷是 SSD
 卷的序列号是 98A5-7F8E

 E:\MySQL\8.0 的目录

2022-07-16  14:14       134,217,728 ib_logfile0
2022-07-03  17:30       134,217,728 ib_logfile1
               2 个文件    268,435,456 字节
               0 个目录 807,501,471,744 可用字节

当前ib_logfile成员为2个,每个128M,后续计划修改为成为3个,每个256M

修改my.ini参数

innodb_log_files_in_group=3
innodb_log_file_size=256M

重启mysql服务

C:\Users\XFF>dir E:\MySQL\8.0\ib_log*
 驱动器 E 中的卷是 SSD
 卷的序列号是 98A5-7F8E

 E:\MySQL\8.0 的目录

2022-07-16  14:19       268,435,456 ib_logfile0
2022-07-16  14:19       268,435,456 ib_logfile1
2022-07-16  14:19       268,435,456 ib_logfile2
               3 个文件    805,306,368 字节
               0 个目录 806,964,072,448 可用字节


mysql> show variables like '%innodb_log_file%';
+---------------------------+-----------+
| Variable_name             | Value     |
+---------------------------+-----------+
| innodb_log_file_size      | 268435456 |
| innodb_log_files_in_group | 3         |
+---------------------------+-----------+
2 rows in set, 1 warning (0.00 sec)

在8.0版本中直接修改成功,如果是以前MySQL版本,修改过程可能遭遇InnoDB: Error: log file ./ib_logfile0 is of different size 0 268435456 bytes错误,类似这样的需要删除ib_logfile文件,启动MySQL服务重新生成ib_logfile文件(在8.0版本中直接自动删除并重建)

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