How to Efficiently Filter Combined Querysets from Multiple Models?

[c0d33py]

HELP WANTED:I have a Django view that combines and sorts querysets from three different models (Event, Subject, and Article) to create a feed. I'm using the sorted function along with chain to merge the querysets and sort them based on the 'created_at' attribute. The feed is then returned as a list.

However, I'm facing challenges when it comes to filtering the feed based on user-provided search and author parameters. Since the feed is in list form, I can't directly use the filter method from the Django QuerySet.

The created_by__username__icontains is not working. Only the ModelChoiceField is working along with it but is want to use CharField field with it.

OR

If anybody have another solution to make the feed. Please share it.

forms.py

class FeedFilterForm(forms.Form):
    author = forms.CharField( # ModelChoiceField
        label='Author',
        required=False,
        # queryset=User.objects.all(),
        widget=forms.TextInput(attrs={'placeholder': 'Author'}),
    )

Views.py

class FeedView(View):
    form_class = YourFormClass
    template_name = 'your_template.html'

    def get_queryset(self):
        """
        Get the combined and sorted queryset from events, subjects, and articles.
        """
        events = Event.objects.all()
        subjects = Subject.objects.all()
        articles = Article.objects.all()

        feed = sorted(
            chain(articles, subjects, events),
            key=attrgetter('created_at'),
            reverse=True,
        )

        queryset = self.filter_queryset(feed)
        return list(queryset)

    def filter_queryset(self, queryset):
        form = self.form_class(self.request.GET)

        if form.is_valid():
            data = form.cleaned_data

            author = data.get('author')
            if author:
                queryset = filter(
                    lambda x: author
                    == getattr(x, 'created_by__username__icontains', ''),
                    queryset,
                )

        return queryset

    def get(self, request, *args, **kwargs):
        queryset = self.get_queryset()

        context = {
            'object_list': queryset,
        }

        return render(request, self.template_name, context)

[carltongibson]

You want to use QuerySet.union() https://docs.djangoproject.com/en/4.2/ref/models/querysets/#union

[c0d33py]

I have three different base models. each model have different field and columns union oprator is getting each UNION query must have the same number of columns LINE 1: ...Y "core_article"."created_at" DESC) UNION (SELECT "core_subj... while run the queryset queryset = articles.union(tickers, events)

[carltongibson]

Yes, so you need to select columns so that the query sets match up...

I just checked, a search for "how to use union django" provides a number of good looking results.