mysql常用命令以及小技巧
作者：礁之
这篇文章主要分享的是mysql常用命令以及小技巧，概述清理二进制日志、mysqldump不锁表、mysql跳过空事务等相关资料展开主题，需要的小伙伴可以参考一下，希望对你有所帮助
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
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)
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
mysql> set gtid_next='81a58913-993d-11eb-94c7-00e0ed7ae706:37497'; Query OK, 0 rows affected (0.00 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 | 81a58913-993d-11eb-94c7-00e0ed7ae706:37497 | | gtid_owned | 81a58913-993d-11eb-94c7-00e0ed7ae706:37497 | | gtid_purged | 81a58913-993d-11eb-94c7-00e0ed7ae706:1 | | session_track_gtids | OFF | +----------------------------------+--------------------------------------------+ 9 rows in set (0.01 sec)
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：
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 | 81a58913-993d-11eb-94c7-00e0ed7ae706:37497 | | gtid_owned | | | gtid_purged | 81a58913-993d-11eb-94c7-00e0ed7ae706:1 | | session_track_gtids | OFF | +----------------------------------+--------------------------------------------+ 9 rows in set (0.00 sec)
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
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