This is the second part of our deep dive into Postgres logical replication. If you haven’t read through part one on replica identity, be sure to che

Postgres Write-Ahead Logs

submited by

Style Pass

2024-09-25 00:00:07

This is the second part of our deep dive into Postgres logical replication. If you haven’t read through part one on replica identity, be sure to check that out. In this part, we’ll discuss how write-ahead logs work, why you want to use them, and their various components and settings.

Write-ahead logs are one of four components required for logical replication. They are used to ensure data durability, meaning your data is consistent and protected against data loss. Even if a server machine fails, write-ahead logs ensure your changes persist.

While WAL is enabled by default in Postgres, it’s important that your disk space meets all of the requirements necessary to use WAL files. You can configure different parameters to determine how much information is written to logs and the amount of shared memory they contain.

Write-ahead logs store each state change as a command with a unique identifier within an append-only file. Each of the commands in this append-only file contains all the information needed to replicate the change.