anchor.diff:      owner  = "citusdata";
       repo   = "postgresql-topn";
       rev    = "refs/tags/v${version}";
  -    sha256 = "05mjzm7rz5j7byzag23526hhsqsg4dsyxxsg8q9ray1rwxjbr392";
  +    sha256 = "0ai07an90ywhk10q52hajgb33va5q76j7h8vj1r0rvq6dyii0wal";
     };
   
     installPhase = ''
  
positive.code: 
  stdenv.mkDerivation rec {
    pname = "pg_topn";
    version = "2.3.0";
  
    buildInputs = [ postgresql ];
  
  
negative.code:   meta = with stdenv.lib; {
      description = "Efficient querying of 'top values' for PostgreSQL";
      homepage    = "https://github.com/citusdata/postgresql-topn";
      changelog   = "https://github.com/citusdata/postgresql-topn/blob/v${version}/CHANGELOG.md";
      maintainers = with maintainers; [ thoughtpolice ];
      platforms   = postgresql.meta.platforms;
      license     = licenses.agpl3;
  