mysql常用命令以及小技巧

1. 清理二进制日志

purge master logs to ‘log-bin.004193’; #表示直接清理到4193位置

2. mysqldump不锁表

在使用mysqldump备份mysql数据时，要尽量去从库拿，如果有需求去主库，可以加 —single-transaction 参数不锁表，不加此参数有可能会把主库的表全锁了！！导致业务出现故障

mysqldump –single-transaction –compact -uroot -p（password） -h（dbip） -d （databasesname） > /tmp/test.sql

3. mysql跳过空事务

问题出现：

Slave_IO_State: Waiting for master to send event
Master_Host: 10.187.97.219
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: log-bin.000047
Read_Master_Log_Pos: 61907358
Relay_Log_File: relay.000114
Relay_Log_Pos: 61906291
Relay_Master_Log_File: log-bin.000047
Slave_IO_Running: Yes
Slave_SQL_Running: No
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 1062
Last_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 1 failed executing transaction ’81a58913-993d-11eb-94c7-00e0ed7ae706:37497′ at master log log-bin.000047, end_log_pos 61906370. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any.
Skip_Counter: 0
Exec_Master_Log_Pos: 61906082
Relay_Log_Space: 61907849
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 1062
Last_SQL_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 1 failed executing transaction ’81a58913-993d-11eb-94c7-00e0ed7ae706:37497′ at master log log-bin.000047, end_log_pos 61906370. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any.
Replicate_Ignore_Server_Ids:
Master_Server_Id: 5345323
Master_UUID: 81a58913-993d-11eb-94c7-00e0ed7ae706
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State:
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp: 210413 05:25:50
Master_SSL_Crl:
Master_SSL_Crlpath:
#master# Retrieved_Gtid_Set: 81a58913-993d-11eb-94c7-00e0ed7ae706:2-37500
#slave# Executed_Gtid_Set: 119cf71e-993c-11eb-94bd-00e0ed93753c:1-3,
#81a58913-993d-11eb-94c7-00e0ed7ae706:1-37496
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)

开始处理：首先我们知道

Executed_Gtid_Set: 119cf71e-993c-11eb-94bd-00e0ed93753c:1-3,
81a58913-993d-11eb-94c7-00e0ed7ae706:1-37496

是slave 已经执行过的事务。

其中：

81a58913-993d-11eb-94c7-00e0ed7ae706:1-37496 是已经回放了的从master 同步的事务，
119cf71e-993c-11eb-94bd-00e0ed93753c:1-3, 是在 slave 上执行的事务

而下面这个是从master 同步的事务，等待slave

Retrieved_Gtid_Set: 81a58913-993d-11eb-94c7-00e0ed7ae706:2-37500

执行停止slave

mysql> stop slave;
Query OK, 0 rows affected (0.00 sec)

检查当前 gtid 相关信息

将事务指向37496 的下一个事务，即 37497，注意规范，把 :1-37396 的 1 去掉

跳过空事务：

mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> commit;
Query OK, 0 rows affected (0.00 sec)

查询gtid 信息：

设置自动分配 GTID：

ysql> set gtid_next=’AUTOMATIC’;
Query OK, 0 rows affected (0.00 sec)

4. 番外

我们知道一个新的事务在提交后会被分配一个新的GTID,当该事务在从库上被应用时会保留主库上的GTID
我们可以通过设定gtid_next 的值来改变这种行为

1 AUTOMATIC

当设置为AUTOMATIC时(默认值)时，系统会自动分配一个GTID，如果事务回滚或者没有写入到二进制文件时则不会分配

2 具体的GTID值

我们可以设置该变量为一个具体的有效的GTID，这时服务器会将该GTID分配给下一个事务，就算该事务没有被写入二进制日志或者为空事务，该GTID也会被分配并加入到gtid_executed变量中
这里需要注意的是，如果该变量值不为AUTOMATIC，我们需要手动的为每个事务指定GTID，否则该事务会失败，你可以将其改为AUTOMATIC，让服务器自动分配

启动 slave：

mysql> start slave;
Query OK, 0 rows affected (0.03 sec)
mysql> show variables like ‘%gtid%’;
+———————————-+—————————————-+
| Variable_name | Value |
+———————————-+—————————————-+
| binlog_gtid_simple_recovery | ON |
| enforce_gtid_consistency | ON |
| gtid_executed | |
| gtid_executed_compression_period | 1000 |
| gtid_mode | ON |
| gtid_next | AUTOMATIC |
| gtid_owned | |
| gtid_purged | 81a58913-993d-11eb-94c7-00e0ed7ae706:1 |
| session_track_gtids | OFF |
+———————————-+—————————————-+
9 rows in set (0.00 sec)
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 10.187.97.219
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: log-bin.000047
Read_Master_Log_Pos: 61907358
Relay_Log_File: relay.000115
Relay_Log_Pos: 448
Relay_Master_Log_File: log-bin.000047
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 61907358
Relay_Log_Space: 61908058
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 5345323
Master_UUID: 81a58913-993d-11eb-94c7-00e0ed7ae706
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set: 81a58913-993d-11eb-94c7-00e0ed7ae706:2-37500
Executed_Gtid_Set: 119cf71e-993c-11eb-94bd-00e0ed93753c:1-3,
81a58913-993d-11eb-94c7-00e0ed7ae706:1-37500
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)

5. mysql8.0使用mysqldump导出数据

导出指定库的所有数据：

./bin/mysqldump -uroot -padmin123 -S status/mysql3306.sock aaa5 –set-gtid-purged=OFF –single-transaction > /root/aaa5.sql

注释：

1.数据库前面不需要加任何参数，如果加-d就是只导出表结构
2.当数据库开启gtid后需要在导出数据时把gtid关掉，即加--set-gtid-purged=OFF参数，因为gtid是唯一的，再插入时会报错
3.加参数–single-transaction不锁表