Question

I am using the django default pagination but I am concerned about its efficiency.I have 3000+ objects stored in my database and I display 15 each page.So every time I go to the next page it seems to me I have do database query again in my views.My code in views.py is just like the code given in the docs of Django.Here is my code:

all_words=Word.objects.all()
    user=request.user
    wordlist = []
    for word in all_words:
        taged_word = FlagWord.objects.filter(word = word,user = user)
        if taged_word :
            usertag = True
        else:
            usertag = False
        wordlist.append({'word':word,'usertag':usertag})
    number = Word.objects.count()
    paginator = Paginator(wordlist,15)
    try:
        page = int(request.GET.get('page','1'))
    except ValueError:
        page = 1

    try:
        listpage = paginator.page(page)
    except (EmptyPage,InvaildPage):
        listpage = paginator.page(paginator.num_pages)
    return render_to_response('GRETemplate/wordbank.html',{'words':listpage,'user':user,'number':number})

It’s like I have my wordlist ready for the first time but I have to do it over and over again when i request for another page.Is there any more efficient way to do this?

Thanks.G

Answer 1

You should ideally cache the results of Word.objects.all() so the system doesn’t hit your db everytime.

However, I think your loop could be simplified a little:

Warning: I haven’t tested it.

Suppose your Word model is:

class Word(models.Model):
   the_word = models.CharField(max_length=200)

First, you get all the flagged words that belong to the current user:

fw = FlagWord.objects.filter(user = user)
if fw.count():
    if fw.word_set.count():
      wordlist.append(
                   dict(('word':obj.the_word,'usertag':True)
                       for obj in fw.word_set.all())

Finally, filter the word list with the other words that didn’t match. I’ve expanded the code since it contains lots of brackets.

wordlist.append(dict(
                      ('word':obj.the_word,'usertag':False)
                      for obj in
                         Word.objects.exclude(
                           the_word__in=fw.values_list('word__the_word',flat=True)
                         )
                     )
               )