Could you explain the principle of logical replication in database management systems?

Logical replication in a DBMS is the process of copying data changes (such as inserts, updates, deletes) from one database (the master) to another (the replica) at the level of logical changes, not physical copying of files or blocks.

Principle of operation:

• Changes in the source database are recorded in the transaction log (WAL).
• Logical replication reads these records and converts them into logical operations (such as SQL queries or data modification commands).
• These operations are transmitted to the replica, where they are applied to the database, keeping it up-to-date.

Advantages:

• You can replicate only selected tables or data.
• The replica can have a different structure or even a different version of the DBMS.
• It allows flexible configuration of the data flow.

Example: in PostgreSQL, logical replication allows subscribing to change publications of specific tables and applying them on the subscriber side.