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MySQL Binlog

By Roja MetlaRoja Metla

MySQL Binlog

Introduction to MySQL Binlog

MySQL Binlog is a binary log, which consists of all the modifications that happened in the database. All the details are written in the server in binary format. To read the contents in the file we use the “mysqlbinlog” utility. The Binary log is useful in the MySQL replication, where the main server will send data from binary logs to the remote servers. Basically, when we perform operations like creating the table or updating the data from the existing table these events details are stored in the binary logs.

In this session let us see in detail the binary log and how it works in MySQL.

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Syntax:

We use below the syntax, to see all the binary logs: –

SHOW BINARY LOGS;/* - - here we are updating the row - - */

Below is the syntax that we use to read the contents of the binary logs.

mysqlbinlog [options] <log_file_name>

MySQL Binary Log

Below are the few options:

  • Debug: This option is used to write a debugging log.
  • Debug-Check: This option is used to print the debugging information when the program exit.
  • Start-DateTime: This option is used to read binary log. Get data when the timestamp equal to or later than DateTime argument specified in the command.
  • Start-Position: This option is used to decode the binary log. Decode from first event with position equal to or greater than argument specified in the command.
  • Stop-DateTime: This option is used to stop reading binary log. Stop reading from first event with a timestamp equal to or greater than datetime argument specified in the command.
  • Stop-Never: This option is used to stay connected to server after reading last binary log file.
  • Stop-Never-Slave-Server-Id: This option is used to make the slave server ID to report when connecting to the server.
  • Stop-Position: This option is used to stop decoding binary log at first event with position equal to or greater than argument specified in the command.
  • To-Last-Log: This option is used when you want to not stop at the end of the requested binary log from a MySQL server and continue printing to the end of the last binary log.
  • User: This option is used to check the MySQL user name used for connecting to the server.
  • Verbose: Reconstruct row events as SQL statements
  • Verify-Binlog-Checksum: This option is used to verify checksum from the binary log.
  • Version: This option is used to display version information and exit.

How Does MySQL Binary Log Work?

Let us see the existing log files present in the server, using the below syntax:

Query:

Show BINARY LOGS

Output:

MySQL Binlog Example 1

Now let us create a table and perform an update on the table and see the binary log creation in the server.

Query:

create table Data_034
(
id int,
name varchar(20),
location varchar(20)
);

Insert data into the table: 

Query:

INSERT INTO DATA_034 VALUES (1, 'Rose', 'United Kingdom' );
INSERT INTO DATA_034 VALUES (2, 'Jack', 'United states') ;
INSERT INTO DATA_034 VALUES (3, 'Will', 'Britain');
INSERT INTO DATA_034 VALUES (4, 'Bentley', ‘USA’);
INSERT INTO DATA_034 VALUES (5, 'Sam', 'Rome');
INSERT INTO DATA_034 VALUES (6, 'Hammington', 'Italy');

Update the table row as below:

Query:

update data_034 set location='Rome' where id=6;/* - - here we are updating the row - - */

Now we have changed the binary log name which is available in the

“c:\ProgramData\MySQL\MySQL Server 8.0\my.ini” to “Binarylog-bin.000001”

Query:

SHOW BINARY LOGS; /* - - to show all the binary logs files - - */

Output:

MySQL Binlog Example 2

Let us read the binary log and see the output: –

To read, we use the mysqlbinlog utility: –

Open command prompt ->go to the path of the “mysqlbinlog” bin as “C:\Program Files\MySQL\MySQL Server 8.0\bin”.

Input:

mysqlbinlog "C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001"
C:\Program Files\MySQL\MySQL Server 8.0\bin>mysqlbinlog "C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001"

Output:

MySQL Binlog Example 3

Example:

The table consists of the below rows in it: –

id Name Location
1 Rose United Kingdom
2 Jack India
3 Will Britain
4 Bentley USA
5 Sam Rome
67 Hammington Rome

Here update the table as below: –

Query:

update data_034 set id=67 where id=6; /* - - here we are updating the row - - */

Below let us get the last log that performed as in the above we are not able to read the binary log: –

Input:

C:\Program Files\MySQL\MySQL Server 8.0\bin>mysqlbinlog  -v "C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001"
/* - - to view the logs in the readable format - - */

Output: 

MySQL Binlog Example 4

Below is the data present in the table after update: –

id Name Location
1 Rose United Kingdom
2 Jack India
3 Will Britain
4 Bentley USA
5 Sam Rome
6 Hammington Rome

Display content in a user-friendly manner: 

Query:

mysqlbinlog <binary_log_file_name>

Example

mysqlbinlog “C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001”

Screenshot for the same:

Display content in a user friendly Example 5

To Display the Events that Happened in Particular Database:

Query:

mysqlbinlog -d crm<binary_log_file_name>
or
mysqlbinlog --databasecrm<binary_log_file_name>

Example

mysqlbinlog-d crm“C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001”
or
mysqlbinlog -databasecrm“C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001”

Screenshot for the Same: 

display the events Example 6

To Control the Binlog Output:

The output can be controlled based on possible values provided. They are: –

  • Never
  • Always
  • Decode-rows
  • Auto (default)

Never:

This will work when there is no event occurred in “row_level”.

mysqlbinlog --base64-output=never "C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001"

Always: 

This will display only the BINLOG entries whenever possible.

mysqlbinlog --base64-output=always "C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001"

Decode-rows: 

This option will decode the row-based events into commented SQL statements.

mysqlbinlog --base64-output=decode-rows "C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001"

Auto: 

mysqlbinlog --base64-output=auto"C:\ProgramData\MySQL\MySQL Server 8.0\Data\Binarylog-bin.000001"

Conclusion – MySQL Binlog

MySQL Binlog is a binary log, which consists of all the modifications that happened in the database. All the details are written in the server in binary format. To read the contents in the file we use the “mysqlbinlog” utility. The Binary log is useful in the MySQL replication, where the main server will send data from binary logs to the remote servers. Basically, when we perform operations like creating the table or updating the data from the existing table these events details are stored in the binary logs.

Recommended Articles

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