Django limit query not working in get_queryset

April 19, 2023

I overwrite get_queryset as below:

    def get_queryset(self, request):
        qs = super().get_queryset(request)
        qs.order_by('-id').all()[:3]
        print(qs)
        print()

        qs2 = CreditsTransaction.objects.all()[:3]
        print(qs2)
        return qs

This is my output:

[2023-04-19 08:53:52 +0000] [1178] [INFO] Booting worker with pid: 1178
<QuerySet [<CreditsTransaction: CreditsTransaction object (623267)>, <CreditsTransaction: CreditsTransaction object (623266)>, <CreditsTransaction: CreditsTransaction object (623265)>, <CreditsTransaction: CreditsTransaction object (623264)>, <CreditsTransaction: CreditsTransaction object (623263)>, '...(remaining elements truncated)...']>

<QuerySet [<CreditsTransaction: CreditsTransaction object (623267)>, <CreditsTransaction: CreditsTransaction object (623266)>, <CreditsTransaction: CreditsTransaction object (623265)>]>

So in qs.order_by('-id').all()[:3] the number of results is not limited to 3. Whereas in CreditsTransaction.objects.all()[:3] it is. I want to know why.

>Solution :

You have a logical error in the code. The line qs.order_by('-id').all()[:3] does not get saved back in qs variable. So, you print the original qs.

You need to do qs = qs.order_by('-id').all()[:3] in order to get what you want.

def get_queryset(self, request):
    qs = super().get_queryset(request)
    qs = qs.order_by('-id').all()[:3]
    print(qs)
    print()

    qs2 = CreditsTransaction.objects.all()[:3]
    print(qs2)
    return qs