Search view with long long parameters

At most of web application have the so-called search view. The view get some request parameters and display some search results by using these parameters.

A search view does not cause any side effects, so it should expect a GET request. The URL will be like this:

/search?code=R100100&code=R1001001

and the view will be like this:

def search_studends_view(request):
    f = SearchForm(data=request.GET)

    students = None
    if f.is_valid():
        codes = f.cleaned_data['code']
        students = get_students(codes=codes)

    return HttpResponse(",".join(students))

(This is a sample code, so I have not verified the correctness of it)

In most cases, the GET search view seems good and enough. But unfortunately, it have some limitations.

With long long parameter

Let’s consider a searching by using very long parameters. If you should create a view that can be OR search by 1,000 birthdays…

The URL will be like this:

/search?code=R100100&code=R100101&code=R100102&code=R102000&code=...

Then, what would happen? (You may have a doubt the requirement itself)

The header of this request will be very long too. so, It will couse “Request URI too large (414)”.

Gunicorn’s maxcimum size of a request line is 4094 bytes by default.

http://docs.gunicorn.org/en/latest/configure.html#limit-request-line

At Nginx, it is 8k bytes.

http://wiki.nginx.org/NginxHttpCoreModule#large_client_header_buffers

If you use reverse proxying, you also should consider settings proxy_buffers, proxy_buffer_size.

だるい。

With POST

Another solution, you can use POST request with search view.

But, if you make the honest, you will run into trouble caused browser history backing. If you back to POST result, most browser will raise warning (like ‘Web page has expired’).

A re-POSTing is handled as bad process to protect such as multiple registration. Also, the POST results will not be cached, because a POST request cause side effect in general. (Some browsers like Chrome, Firefox will cache it. but IE will not so even if you provide Cache-Controll header)

To avoid this, you should redirect to a GET result page after POSTed. POSTed parameter will store to session, and GET page display by using it.

like this:

def search_studends_view(request):
    if request.method == 'POST':
        request.session['search_params'] = request.POST
        return HttpResponseRedirect('/search')
    else:
        try:
            params = request.session['search_params']
        except KeyError:
            params = {}
        f = SearchForm(data=params)

        students = None
        if f.is_valid():
            codes = f.cleaned_data['code']
            students = get_students(codes=codes)

        return HttpResponse(",".join(students))

(Yes, this is a just sample code)

It is not beautiful.

If you want to paginate these results you shuould get a page number from GET parameter (puke).