rulerConfig = {
    groups = [ {
      name = "postgresql";
      rules = [ {
        alert = "PostgresqlCollationMismatch";
        expr = ''
          {unit="postgresql.service"}
            |~ "WARNING:  database \"[^\"]+\" has a collation version mismatch"
            | regexp "database \"(?<database>[^\"]+)\""
        '';
        labels.severity = "warning";
        annotations.summary = "PostgreSQL database {{ $labels.database }} on {{ $labels.machine }}i reports database collation mismatch";
      } ];
    } ];
  };

# lokitool rules lint ruler.yml 
ERRO[0000] unable parse rules file                       error="could not parse expression for alert 'PostgresqlCollationMismatch' in group 'postgresql': parse error at line 1, col 19: syntax error: unexpected IDENTIFIER" file=ruler.yml
lokitool: error: prepare operation unsuccessful, unable to parse rules files: file read error, try --help