anchor.diff:    postgresql_10 = self.callPackage generic {
       version = "10.21";
       psqlSchema = "10.0"; # should be 10, but changing it is invasive
  -    sha256 = "sha256-0yGYhW1Sqab11QZC74ZoesBYvW78pcntV754CElvRdE=";
  +    hash = "sha256-0yGYhW1Sqab11QZC74ZoesBYvW78pcntV754CElvRdE=";
       this = self.postgresql_10;
       thisAttr = "postgresql_10";
       inherit self;
  
positive.code: 
      src = fetchurl {
        url = "mirror://postgresql/source/v${version}/${pname}-${version}.tar.bz2";
        inherit sha256;
      };
  
      hardeningEnable = lib.optionals (!stdenv.cc.isClang) [ "pie" ];
  
negative.code:   postgresql_13 = self.callPackage generic {
      version = "13.7";
      psqlSchema = "13";
      hash = "sha256-G5Bb9PPYNhSjk7PFH9NFkQ/SYeT1Ekpo2aH906KkY5k=";
      this = self.postgresql_13;
      thisAttr = "postgresql_13";
      inherit self;
  