MySql data recovery method personal summary

I. Introduction

mysql has the binlog function, which can record the operations performed on the table and the executed SQL statements;

The following mainly summarizes the opening method and usage method of binlog;

If you delete some data in the database table by mistake, or delete the entire table by mistake, modify the table structure by mistake, etc., you can use this method to restore.

Second, Steps

1. If you want to use the MySql data recovery function, you first need to modify the Mysql configuration file and enable the binlog function.(Some versions of binlog are not enabled by default, so you need to manually modify the configuration file to enable)

(1)windows environment
The name of the configuration file is my.ini, you can install the software everything to search for this file.A sample path is as follows:

C:ProgramDataMySQLMySQL Server 5.7my.ini

(2) linux environment
The name of the configuration file is my.cnf, you can use the find command to search for the location of the file:

sudo find / -name my.cnf

A sample location is as follows:

/etc/my.cnf

2. After finding the configuration file (my.ini/my.cnf), add the following configuration (of course, first check whether the configuration file has already configured this line, do not repeat it):

log-bin=mysqlbinlogbinlog-format=ROW

Or you can specify the location of binlog (the path under linux is below):

log-bin=/data/mysql/log/mysqlbinlogbinlog-format=ROW

Note that when binlog is specified in a folder, you must create a folder yourself, otherwise restarting mysql will report an error.

3. After the configuration is complete, restart mysql.

4. Now, operations on MySQL databases, tables, data, etc., and execution of additions, deletions, and changes to sql will all be recorded in binlog.(Search for mysqlbinlog to find this log file)

5. To test, create a new table binlog_test with random columns, then write a few lines of data, and then clear the table data.(ready to use binlog to restore data)

6. The command to view binlog is as follows:

mysql> show binlog events; #Only view the contents of the first binlog filemysql> show binlog events in 'mysqlbinlog.000002';#View the contents of the specified binlog filemysql> show binary logs; #Get a list of binlog filesmysql> show master status; #View the binlog file currently being written

7. First look at which binlog is currently used:

show master status;

After I executed it, I found that the currently used binlog is: mysqlbinlog.000004

8. Then check the contents of this binlog:

 show binlog events in 'mysqlbinlog.000004';

After execution, you can find the sql of the binlog_test table you just created in the Info column of the query result (the corresponding Event_type is >Query);

You can see the record row that just emptied the table data, Event_type is Delete_rows;

In the above, you can see that after the table is created, the Event_type of the new data is Write_rows;

9. Analyze this binlog, our goal is to restore the data that was just deleted, so after finding the create table statement, the first Event_type is the line of Query,Its Pos is 460;
Then find Event_type which is the closest, above Delete_rowsInfo is the line of COMMIT, its Event_type is Xid, End_log_pos is 1199.

(End_log_pos of each line corresponds to Pos of the next line)

10. Now I have found a range of execution logs from 460 to 1199, which is the log of adding data to the table binlog_test, so as long as the operations in between are repeated, the data can be restored.

11-1.windows, find the location of mysqlbinlog.exe;
under linux, find the location of mysqlbinlog (this is in the bin directory of mysqlan executable file);
Then execute the following command to restore the data:

mysqlbinlog --no-defaults --start-position=460 --stop-position=1199 "C:ProgramDataMySQLMySQL Sever 5.7Datamysqlbinlog.000004" -d test | mysql -uroot -proot test

The specified start position is 460 and the end position is 1199. After the command is executed, the command within the specified range in the log will be read and executed again.
The meanings of other commands are:

"-d test" means, specify the database as test (binlog_test table is in the test database)"|" is the pipe character"mysql -uroot -proot test" is the mysql account password, log in to the target database"-uroot": account is root"-proot": password is root"test": the database is test

11-2. You can also export the logs within the specified range in the binlog log, and then execute the source command to restore the data, as follows:

mysqlbinlog "C:ProgramDataMySQLMySQL Sever 5.7Datamysqlbinlog.000004" -d test --skip-gtids --start-position=460 --stop-position=1199 > test.sql

After executing this command, the logs in the specified range are exported to test.sql;
Then log in to mysql and execute the command:

mysql> use test;mysql> source test.sql;

This will restore the data.

III. Other Notes

1. If you use truncate to delete table data, a few lines of records will be added to binlog to record the truncate operation. Examples are as follows:

mysqlbinlog.000004 | 3122 | Query | 1 | 3211 | use 'test'; TRUNCATE 'binlog_test'

If you want to restore the data, you need to find the Pos where the data was first inserted, to the End_log_pos before the truncate, and then re-execute the commands during this period.

2. The addition, deletion and modification operations will be recorded in the binlog, and the slow query sql can also be recorded in the slow query log, but you also need to modify the configuration file to open the slow query log.

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