anchor.diff:  
   stdenv.mkDerivation rec {
     pname = "pg_hll";
  -  version = "2.15";
  +  version = "2.15.1";
   
     buildInputs = [ postgresql ];
   
  
positive.code:     owner  = "citusdata";
      repo   = "postgresql-hll";
      rev    = "refs/tags/v${version}";
      sha256 = "19d50cvp3byjyr2dc5rjmyrlp97bb19mz0ykr3w4iyc6qi5d5qj2";
    };
  
    installPhase = ''
  
negative.code: 
    meta = with stdenv.lib; {
      description = "HyperLogLog for PostgreSQL";
      homepage    = "https://github.com/citusdata/postgresql-hll";
      changelog   = "https://github.com/citusdata/postgresql-hll/blob/v${version}/CHANGELOG.md";
      maintainers = with maintainers; [ thoughtpolice ];
      platforms   = postgresql.meta.platforms;
      license     = licenses.asl20;
  