I’ve been working on getting the pg_database_size so that I can get it displayed on my grafana dashboard, but I ran into an issue getting it to work on an AWS RDS database even though it worked just fine on a self hosted postgresql database.

I’m using this postgres_exporter docker image that comes with this pg_database_size query by default:

pg_database:
  query: " SELECT pg_database.datname, pg_database_size(pg_database.datname) as size FROM pg_database"

If you connect to your rds pg database and run that query yourself you will run into an error something along the lines of not having access to the rdsadmin db. We really don’t need access to the rdsadmin db anyways so we can modify this query to exclude this db so that pg doesn’t return an error and we can easily get the db sizes of all the other dbs that we do have access to. Here is the modified query:

pg_database:
  query: " SELECT pg_database.datname, pg_database_size(pg_database.datname) as size FROM pg_database WHERE datname != 'rdsadmin'"