MariaDB replicate do db is a replication Filter option for MariaDB. We answer all questions, no matter how big or small, at Bobcares as part of our Server Management Services.

What is MariaDB replicate do db?

We can configure a replication slave to apply statements and transactions affecting databases that match a given name by setting the replicate do db system variable. Replicate do-db instructs the slave to only read relay log entries for the specified database. Since there is no relay log to read from, replicate do db has no impact on the master. The lock tables component ensures that the data is reliable.

The system will not work for:

• Cross-database updates with statement-based logging
• Mixed-based logging and the statement is logged statement based

Only the default database (i.e., the one chosen by USE) and not any explicitly mentioned tables in the query are taken into account for statement-based replication. When an event login its statement-based format, replicate do db will test the filter against the default database.

However, The system variable will accept a list of filters when set dynamically with SET GLOBAL. It is not possible to specify database names that contain commas while setting it dynamically. So to specify database names with commas, they must be specified via command line options. When setting it dynamically, the slave threads must stop.

Example:

STOP SLAVE;
SET GLOBAL replicate_do_db='db1,db2';
START SLAVE;

The system variable does not accept lists that separate each other by a comma when set via the command line. So to specify the system variable more than once if we need to specify multiple filters.

Example:

[mariadb]
...
replicate_do_db=db1
replicate_do_db=db2

The slave will do the following:

• Replicate the database db1’s statements and transactions
• Replicate the database db2’s statements and transactions
• Don’t give importance to any transactions or statements that affect other databases

How Replication Functions?

Let’s also see how replication works.

• Master’s binary log records all the transactions.
• The slave writes the transactions to its relay log after reading them from the master’s binary log
• The slave doesn’t start running the statements from its relay log until after that

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Conclusion

In this article, We have seen the information provided by our Support team on MariaDB replicate do db. This includes examples and also pointed out the conditions when this filter doesn’t work.