Docs feedback: POSTGRES_VERSION

I am new to Kubernetes and GitLab Auto DevOps so I rely on good documentation to get started. I want to switch from running my pretty standard Rails app from AWS EC2 and RDS Postgres 10.6 to using GitLab Auto DevOps with a Kubernetes cluster on DigitalOcean. To stay away from problems from switching the Postgres version, I want to keep exactly the same one when I migrate.

The way I understand the GitLab Auto DevOps documentation I can change the POSTGRES_VERSION environment variable to choose my preferred version of Postgres. When I tried to set the value to 10.6 and ran the Auto DevOps pipeline, I realized that there are two different docker images being used for tests and deployment. While the Auto DevOps tests use _/postgres as described in the documentation, the final deployment actually uses bitnami/postgresql which uses a different naming convention for tags. While the tag 10.6 exists in _/postgres, the proper tag name for bitnami/postgresql would be 10.6.0.

I tried to find out why the deployment and test stages use different docker images and followed the trail:

  1. The Customize values for Helm Chart docs point to default Helm chart.
  2. This git repo has a deprecation notice and points to auto-deploy-image.
  3. The Helm chart in auto-deploy-image references the stable/postgresql Helm chart 0.7.1.
  4. The master branch of that repo has yet another deprecation notice and points to bitnami/charts.
  5. Looking through the bitnami charts I finally find the bitnami/postgresql Helm chart, which uses docker images from bitnami/postgresql.

I didn't check all the versions and I am not sure if I really followed the trail of dependencies properly, but I can say for sure that I end up with a bitnami/postgresql running in my Kubernetes cluster. I fixed my issue by setting the version to 10 which exists in both docker hub registries. It would be great to update the docs and make things a bit more clear maybe.