@bachp, thanks for your PR! By analyzing the history of the files in this pull request, we identified @edolstra, @MarcWeber and @peti to be potential reviewers.

could be added to release notes.

Can somebody point me to where the releasenote cam be updated?

The 17.09 release notes are part of the nixos manual and you can build it with
nix-build ./nixos/release.nix -A manual.x86_64-linux

I tried to add this the information to the release notes but I'm strugling to get the docbook syntax right. I first need to find some time to dig into this. So if somebody else is willing to write the entry please feel free to step up 😉

+1 on this change.

What about having the following change as well?

{
  dataDir = mkOption {
    default = 
      if versionAtLeast config.system.stateVersion "17.09" 
      then "/var/db/postgresql/${config.services.postgresql.package.psqlSchema}"
      else "/var/db/postgresql";
  };
}

Including the schema version (like "9.6") in the dataDir has the advantage that it's easier running multiple different versions of postgresql side by side. More importantly it makes running pg_upgrade easier.

Ubuntu, Debian and Gentoo do this as well.

@balajisivaraman I tought about this aswell. I f no objections are there I will add the schema version to the path.

I added the change proposed by @balajisivaraman

@bachp I think you are mentioning me by mistake in this thread. Just letting you know so you can tag the correct person. 👍

@balajisivaraman Sorry I did this on my mobile 😉 I actually wanted to mention @basvandijk.

Looks good to me.

Added some release notes to the branch. @bachp if you can rebase the branch I will merge it.

I'm thinking if changing the data dir to /var/db makes sense. I would rather keep it in /var/lib as this is more common. See also discussion in #25931.

@bachp I would also slightly prefer that the default is moved to /var/lib/postgresql/$psqlSchema since most applications store state under /var/lib and other distributions also store their PostgreSQL databases under /var/lib:

I just noticed that the release note I added already mentions /var/lib/postgres as I assumed that we followed convention with other distros ^_^

@zimbatm @basvandijk I rebase the PR and change the path to /var/lib so it is consistent with the changelog.

!!