{ config, pkgs, ... }:

{
  services.prometheus.exporters.postgres = {
    enable = true;
    listenAddress = "localhost";
    runAsLocalSuperUser = true;

    extraFlags = let
      extraQuery = pkgs.writeText "prometehus-postgres-query.yaml" ''
        pg_database:
          query: "SELECT pg_database.datname, pg_database_size(pg_database.datname) as size FROM pg_database"
          metrics:
            - datname:
                usage: "LABEL"
                description: "Name of the database"
            - size:
                usage: "GAUGE"
                description: "Disk space used by the database"
      '';
    in [
      "--extend.query-path=${extraQuery}"
    ];
  };
  
  services.prometheus.scrapeConfigs = [
    {
      job_name = "postgres";
      static_configs = [{
        targets = [ "localhost:${toString config.services.prometheus.exporters.postgres.port}" ];
      }];
    }
  ];
}