Use Q object and Paginator together in Django - django

Question

I've created View which filters data by search query given in textbox. As well as I used Paginator to show data divided into pages.
My problem is, when I filter data with Q object then and try to paginate by clicking the next button, all data is refreshed.
When I search text by Q object the URL becomes http://127.0.0.1:8000/mael/parties/?q=keyword
And from clicking the next button the URL becomes http://127.0.0.1:8000/mael/parties/?page=2
When I manually change URL http://127.0.0.1:8000/mael/parties/?q=keyword&page=2, then it works. But I don't know how to do this in code.
Is it possible to use Q object search and pagination together?
My View
from mael.models import PartyTotalBillsView
from django.views.generic import ListView
from django.db.models import Q
from django.http import HttpResponseRedirect
class PartyListView(ListView):
paginate_by = 2
model = PartyTotalBillsView
def parties(request):
# Show all records or searched query record
search_text = request.GET.get('q','')
try:
if search_text:
queryset = (Q(party_name__icontains=search_text))
party_list = PartyTotalBillsView.objects.filter(queryset).order_by('party_name')
else:
# Show all data if empty keyword is entered
party_list = PartyTotalBillsView.objects.order_by('party_name')
except PartyTotalBillsView.DoesNotExist:
party_list = None
paginator = Paginator(party_list, 2) # Show 2 rows per page: for Test
page_number = request.GET.get('page')
party_list = paginator.get_page(page_number)
return render(request, 'mael/parties.html', {'party_list': party_list})
Template file
<form id="search-form" method="get" action="/mael/parties/">
<input id="search-text" type="text" name="q" placeholder="Enter search keyword">
<input class="btn-search-party" type="submit" value="Search" />
</form>
<br/>
<table class="show-data">
<thead>
<tr>
<th>ID</th>
<th>Party Name</th>
<th>Total Bill Amount</th>
<th>Phone</th>
<th>Address</th>
<th></th>
</tr>
</thead>
{% if party_list %}
<tbody>
{% for party in party_list %}
<tr>
<td class="party-id">{{ party.party_id }}</td>
<td class="party-name">{{ party.party_name }}</td>
<td>{{ party.total_bills }}</td>
<td class="party-phone">{{ party.party_phone }}</td>
<td class="party-address">{{ party.party_address }}</td>
<td>
<button class="btn-modify" data-partyid="{{party.party_id}}" type="buttton">
Modify
</button>
</td>
</tr>
{% endfor %}
</tbody>
{% endif %}
</table>
<div class="pagination">
<span class="step-links">
{% if party_list.has_previous %}
« first
previous
{% endif %}
<span class="current">
Page {{ party_list.number }} of {{ party_list.paginator.num_pages }}
</span>
{% if party_list.has_next %}
next
last »
{% endif %}
</span>
</div>

Answer 1

Please do not use two views. A ListView can perform filtering as well:
class PartyListView(ListView):
paginate_by = 2
model = PartyTotalBillsView
template_name = 'mael/parties.html'
context_object_name = 'party_list'
def querystring(self):
qs = self.request.GET.copy()
qs.pop(self.page_kwarg, None)
return qs.urlencode()
def get_queryset(self):
qs = super().get_queryset()
if 'q' in self.request.GET:
qs = qs.filter(party_name__icontains=self.request.GET['q'])
return qs.order_by('party_name')
In the links for the previous and next pages, you then append the querystring of the view:
<span class="step-links">
{% if party_list.has_previous %}
« first
previous
{% endif %}
<span class="current">
Page {{ page_obj.number }} of {{ page_obj.paginator.num_pages }}
</span>
{% if party_list.has_next %}
next
last »
{% endif %}
</span>

Answer 2

Pagination & CBV
If you are using django generic ListView with paginate_by attribute, you don't need to build paginator instance. Either you use CBV (Class Based View) or Function Views but not both.
For HTML display create a _django_pager.html page to include in your list pages.
{% comment %}
https://getbootstrap.com/docs/4.1/components/pagination/
{% endcomment %}
{% if is_paginated %}
<ul class="pagination">
{% if page_obj.has_previous %}
<li class="page-item"><a class="page-link" href="?{% url_replace page=page_obj.previous_page_number %}">«</a></li>
{% else %}
<li class="page-item disabled">«</li>
{% endif %}
{% for i in page_obj.paginator.page_range %}
{% if page_obj.number == i %}
<li class="page-item active">{{ i }}<span class="sr-only">(current)</span></li>
{% else %}
<li class="page-item"><a class="page-link" href="?{% url_replace page=i %}">{{ i }}</a></li>
{% endif %}
{% endfor %}
{% if page_obj.has_next %}
<li class="page-item"><a class="page-link" href="?{% url_replace page=page_obj.next_page_number %}">»</a></li>
{% else %}
<li class="page-item disabled">»</li>
{% endif %}
</ul>
{% endif %}
Filtering
Q object is powerfull for building complex query but you have to specify DB field under which Q object applies.
Instead of hardcoding the form in HTML I recommand to use a Form Class. So in forms.py create a PartySearchForm
class PartySearchForm(forms.Form):
"""
Search in party
"""
search_text = forms.CharField(max_length=100,
required=False,
widget=forms.TextInput(attrs={
"class": "form-control",
"placeholder": "Search"
})
)
Option 1: filter queryset in view
class PartyListView(ListView):
model = PartyTotalBillsView
form = PartySearchForm
paginate_by = 100
def build_where(self):
where = Q(pk__gt=0)
if self.request.GET.get("search_text"):
search_list = self.request.GET.get("search_text", None).split()
for search_item in search_list:
where &= (
Q(party_name__icontains=search_item)
)
return where
def get_queryset(self):
qs = self.model.objects.all()
qswhere = qs.filter(self.build_where())
# first param must be request.GET or None (essential for the first load and initial values)
# https://www.peterbe.com/plog/initial-values-bound-django-form-rendered
self.form = PartySearchForm(self.request.GET or None)
return qswhere
In the build_where function you can add as many search field as you want. You can search on other DB field than party_name by adding the fields to the where variable.
where &= (
Q(party_name__icontains=search_item)
| Q(party_location__icontains=search_item)
)
You can also add other search fields than search_text in your form and add Q search on the where variable.
if self.request.GET.get("my_new_field"):
where &= Q(supplier=self.request.GET.get("my_new_field", ""))
Key point here is the get_queryset method where the displayed queryset is defined, ie: fetched, filtered and sorted (which could also be a method). .order_by('party_name') is not useful if you add a class Meta in models.py
class Meta:
verbose_name = "Let's go party"
ordering = ['party_name']
One other way to do would be to pass the queryset to the form and perform the search
Option 2: filter queryset in form
Looks even cleaner with the search logic in the SearchForm only!
PartyListView.get_queryset become
def get_queryset(self):
qs1 = self.model.objects.all()
self.form = PartySearchForm(self.request.GET, queryset=qs1)
qs = self.form.get_queryset(self.request.GET)
return qs
PartySearchForm become
class PartySearchForm(forms.Form):
"""
Search in party
"""
search_text = forms.CharField(max_length=100,
required=False,
widget=forms.TextInput(attrs={
"class": "form-control",
"placeholder": "Search"
})
)
def __init__(self, *args, **kwargs):
"""
Takes an option named argument ``queryset`` as the base queryset used in
the ``get_queryset`` method.
"""
self.queryset = kwargs.pop("queryset", None)
super().__init__(*args, **kwargs)
def get_queryset(self, request):
where = Q(pk__gt=0)
# is_valid() check is important to get access to cleaned_data
if not self.is_valid():
return self.queryset
search_text = self.cleaned_data.get("search_text").strip()
if search_text:
search_list = search_text.split()
for search_item in search_list:
where &= (
Q(party_name__icontains=search_item)
)
qs = self.queryset.filter(where)
return qs.distinct()
Eventually, if you are using Postgres DB and want to go deeper with Text Search you can implement Django full text search. Pros & cons can be gained by reading this.