What does the dash (-) in the Value really means for Aurora PostgreSQL Parameter Group

0

Hi, I am trying to work out what are the supposedly 'default' settings of parameters from the AWS console. I can see the Source column showing Engine default, System default, Modified.

I guess Modified is what we have set manually to non-default settings. For the Engine and System ones, some in the Value field has dash (-), what does this actually mean? How are the set or what set them to what values they may be in the instance/database?

I can't see any explanation of this from https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraPostgreSQL.Reference.ParameterGroups.html or maybe I just missed it somewhere.

asked 13 days ago19 views
1 Answer
0

The dash (-) in the Value field for Aurora PostgreSQL Parameter Groups typically indicates that the parameter is using its default value, which is determined by the database engine itself. This means that the parameter has not been explicitly set in the parameter group and is instead relying on the built-in default value provided by PostgreSQL.

For parameters marked as "Engine default" or "System default" in the Source column:

  1. Engine default: These are parameters with values predetermined by the PostgreSQL engine. The dash indicates that the parameter is using this built-in default value.

  2. System default: These are parameters that AWS RDS has optimized for the Aurora PostgreSQL environment. The dash here also means the parameter is using the AWS-optimized default value.

In both cases, the actual value being used may not be visible in the parameter group settings, but it is applied to your database instance or cluster. To see the actual values in use, you can query the PostgreSQL system catalog. For example, you can run the following SQL query on your Aurora PostgreSQL instance:

SELECT name, setting, boot_val, reset_val, unit
FROM pg_settings
ORDER BY name;

This query will show you the current settings (setting), the boot value (boot_val), and the reset value (reset_val) for all parameters, including those that show a dash in the AWS console.

It's important to note that some parameters in Aurora PostgreSQL are managed at the cluster level, while others are managed at the instance level. This distinction affects how and where these parameters are configured and applied.

If you need to modify these parameters from their default values, you can create a custom parameter group and explicitly set the desired values. However, be cautious when changing parameters, as improper settings can affect database performance and stability.
Sources
Working with parameters on your RDS for PostgreSQL DB instance - Amazon Relational Database Service
Oracle instance parameters and Amazon RDS parameter groups - Oracle to Aurora PostgreSQL Migration Playbook
Overview of parameter groups - Amazon Relational Database Service

profile picture
answered 13 days ago

You are not logged in. Log in to post an answer.

A good answer clearly answers the question and provides constructive feedback and encourages professional growth in the question asker.

Guidelines for Answering Questions