Django Inline for ManyToMany generate duplicate queries

Question

I\'m experiencing some major performing issue with my django admin. Lots of duplicate queries based on how many inlines that I have.

models.py

class          


        

Answer 1

I've assembled a generic solution based on @makaveli's answer that doesn't seem to have problem mentioned in the comments:

class CachingModelChoicesFormSet(forms.BaseInlineFormSet):
    """
    Used to avoid duplicate DB queries by caching choices and passing them all the forms.
    To be used in conjunction with `CachingModelChoicesForm`.
    """

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        sample_form = self._construct_form(0)
        self.cached_choices = {}
        try:
            model_choice_fields = sample_form.model_choice_fields
        except AttributeError:
            pass
        else:
            for field_name in model_choice_fields:
                if field_name in sample_form.fields and not isinstance(
                    sample_form.fields[field_name].widget, forms.HiddenInput):
                    self.cached_choices[field_name] = [c for c in sample_form.fields[field_name].choices]

    def get_form_kwargs(self, index):
        kwargs = super().get_form_kwargs(index)
        kwargs['cached_choices'] = self.cached_choices
        return kwargs


class CachingModelChoicesForm(forms.ModelForm):
    """
    Gets cached choices from `CachingModelChoicesFormSet` and uses them in model choice fields in order to reduce
    number of DB queries when used in admin inlines.
    """

    @property
    def model_choice_fields(self):
        return [fn for fn, f in self.fields.items()
            if isinstance(f, (forms.ModelChoiceField, forms.ModelMultipleChoiceField,))]

    def __init__(self, *args, **kwargs):
        cached_choices = kwargs.pop('cached_choices', {})
        super().__init__(*args, **kwargs)
        for field_name, choices in cached_choices.items():
            if choices is not None and field_name in self.fields:
                self.fields[field_name].choices = choices

All you'll need to do is subclass your model from CachingModelChoicesForm and use CachingModelChoicesFormSet in your inline class:

class ArrangementInlineForm(CachingModelChoicesForm):
    class Meta:
        model = Arrangement
        exclude = ()


class ArrangementInline(admin.TabularInline):
    model = Arrangement
    extra = 50
    form = ArrangementInlineForm
    formset = CachingModelChoicesFormSet