Answers CouchDB

  • Define a view in MapReduce that contains, for each theatre, the films presented in it. Hint: You do not need a reduce here.
function(doc) {
    if(doc.feed.theaterShowtimes[0]) {
        var movieTheater = doc.feed.theaterShowtimes[0].place.theater;
        var moviesOnShow = doc.feed.theaterShowtimes[0].movieShowtimes;

        var movies = [];
        for(var i=0; i < moviesOnShow.length; i++) {
            var movie = moviesOnShow[i].onShow.movie;
            movies.push(movie.title);
        } // for

        emit(movieTheater.name, movies);
    } // if
} // func
  • Modify your previous answer and filter the theaters outside Grenoble (e.g., do not include the theatres in Saint Martin d’Hères).
function(doc) {
    if(doc.feed.theaterShowtimes[0]) {
        var movieTheater = doc.feed.theaterShowtimes[0].place.theater;
        var moviesOnShow = doc.feed.theaterShowtimes[0].movieShowtimes;

        var movies = [];
        if(movieTheater.city == "Grenoble") {
             for(var i=0; i < moviesOnShow.length; i++) {
                 var movie = moviesOnShow[i].onShow.movie;
                 movies.push(movie.title); 
             } // for

             emit(movieTheater.name, movies);

         } // if
     } // if
} // func
  • Give the number of films that each theatre is presenting. Hint: You need a reduce here.
// Map
function(doc) {
    if(doc.feed.theaterShowtimes[0]) {
        var movieTheater = doc.feed.theaterShowtimes[0].place.theater;
        var moviesOnShow = doc.feed.theaterShowtimes[0].movieShowtimes;

        for(var i=0; i < moviesOnShow.length; i++) {
            emit(movieTheater.name, 1);
        } // for

     } // if
} // func


// Reduce
function (key, values) {
    return sum(values) ;
}
  • Give the list of films with a press rating higher than 4 stars. Attention: filter duplicates.
// Map
function(doc) {
    if(doc.feed.theaterShowtimes[0]) {
        var movies = doc.feed.theaterShowtimes[0].movieShowtimes;
        for(var i=0; i < movies.length; i++) {
            var movie = movies[i].onShow.movie;
            if(movie.statistics.pressRating > 4) {
                emit([movie.title, movie.statistics.pressRating], null);
            }
         } // for
    } // if
} // func

 
// Reduce
function (keys,values) {
    return null ;
}
  • Give the list of films presented 2 years ago (10.12.2011), and for each film, the theatre where it was presented and its schedule.
function(doc) {
    if(doc.feed.theaterShowtimes[0]) {
        var movieTheater = doc.feed.theaterShowtimes[0].place.theater;
        var moviesOnShow = doc.feed.theaterShowtimes[0].movieShowtimes; 

        for(var i=0; i < moviesOnShow.length; i++) {
            var movie = {
                "title":   moviesOnShow[i].onShow.movie.title,
                "theater": movieTheater.name,
                "date":    moviesOnShow[i].scr[0].d,
                "schedule": []
            };

            if(movie.date == "2011-12-09") {
                var showTime = moviesOnShow[i].scr[0].t;
                for(var j=0; j < showTime.length; j++) {
                    movie.schedule.push( showTime[j].$ );
                }
                emit(movie.title, movie);
            } // if
        }  // for
    }  // if
}  // func
  • BONUS! Give the list of films, and for every film, the list of theatres that present it (this question is a challenge but we encourage you to try to solve it).
// Map
function(doc) {
    if(doc.feed.theaterShowtimes[0]) {
        var movieTheater = doc.feed.theaterShowtimes[0].place.theater;
        var moviesOnShow = doc.feed.theaterShowtimes[0].movieShowtimes;
        for(var i=0; i < moviesOnShow.length; i++) {
            var movie = moviesOnShow[i].onShow.movie;
            emit(movie.title, movieTheater); 
        } // for
    } // if
} // func


// Reduce
function(keys, values) {
    var movieTheaters = [] ; 
    for(var i=0; i<values.length; i++) {
        var theater = values[i].name;
        if(!contains(movieTheaters, theater)) {
            movieTheaters.push(theater);
        }
    } // for
    return [ movieTheaters.length, movieTheaters ];
} // func
 
function contains(array, element) {
    var isContained = false;
    for(var i=0; i<array.length; i++) {
        if(array[i] == element){
            isContained = true;
            break;
        }
    } // for
    return isContained;
} // func