Postgres Change Data Capture

Change data capture (CDC) is a technique for tracking changes to data in a database. This can be useful for a variety of purposes, such as keeping a historical record of changes, replicating data to other systems, or triggering alerts when certain data changes occur.

PostgreSQL offers a number of different CDC methods, including logical decoding, physical replication, and point-in-time recovery (PITR). In this article, we will focus on logical decoding, which is the most commonly used CDC method for PostgreSQL.

Logical Decoding

Logical decoding is a feature of Postgres Change Data Capture that allows you to stream changes to data as they occur. This is done by capturing changes to the Write-Ahead Log (WAL), which is a record of all changes that have been made to the database.

When a change is made to the WAL, it is decoded into a format that can be easily consumed by other applications. This allows you to build real-time applications that can react to changes in the database as they happen.

Benefits of Logical Decoding

There are a number of benefits to using logical decoding for CDC, including:

• Real-time data capture: Logical decoding allows you to capture changes to data as they occur, which can be useful for building real-time applications.
• Low overhead: Logical decoding has a very low overhead, which means that it does not impact the performance of your database.
• Flexible data format: The data that is captured by logical decoding can be in a variety of formats, including JSON, CSV, and XML. This makes it easy to integrate with other applications.

Limitations of Logical Decoding

There are a few limitations to using logical decoding for CDC, including:

• Not all changes are captured: Logical decoding does not capture all changes to data. For example, it does not capture changes to data that are made through the use of triggers.
• Can be complex to set up: Logical decoding can be complex to set up, especially if you are not familiar with PostgreSQL internals.

Conclusion

Logical decoding is a powerful tool for CDC in Postgres Change Data Capture. It offers a number of benefits, including real-time data capture, low overhead, and flexible data format. However, it is important to be aware of the limitations of logical decoding before you use it.

If you are looking for a way to track changes to data in PostgreSQL, logical decoding is a great option. It is a powerful tool that can be used to build real-time applications, replicate data to other systems, or trigger alerts when certain data changes occur.