我有这样一个模型：

class DataMapping(models.Model):
    company = models.ForeignKey(Company, on_delete=models.CASCADE)
    location = models.ForeignKey(Location, null=True, blank=True, on_delete=models.CASCADE)
    department = models.ForeignKey(LocationDepartment, null=True, blank=True, on_delete=models.CASCADE)
    catagory = models.ForeignKey(CompanyCategory, on_delete=models.CASCADE)
    reason = models.ForeignKey(ReasonForProcessing, on_delete=models.CASCADE)

        class Meta:
            constraints = [
                UniqueConstraint(
                    name='unique_data_map', 
                    fields=['company', 'location', 'department', 'catagory', 'reason'],
                    condition=Q(location__isnull=False),
                    violation_error_message="This data map has already been added.",
                ),
                UniqueConstraint(
                    name='unique_data_map_both_none_dep_none', 
                    fields=['company', 'location', 'catagory', 'reason'],
                    condition=Q(department__isnull=True),
                    violation_error_message="This data map has already been added."
                ),
                UniqueConstraint(
                    name='unique_data_map_both_none', 
                    fields=['company', 'catagory', 'reason'],
                    condition=Q(location__isnull=True) & Q(department__isnull=True),
                    violation_error_message="This data map has already been added."
                )
    ]

基本的模型

class DataMapForm(forms.ModelForm):
    class Meta:
        model = DataMapping
        fields = (
            'location',
            'department',
            'catagory',
            'reason',
    )
    widgets = {
        'company': forms.HiddenInput()
    }

以及以下视图：

def data_mapping_new(request):
    company = get_current_logged_in_company(request)

    if request.method == "POST":
        form = DataMapForm(request.POST or None)
        if form.is_valid():
            catagory = form.save(commit=False)
            catagory.company = company
            if form.is_valid():
                form.save()

我在不同的模型上有一个类似的设置，工作正常，但这个只是引发了一个错误django.db.utils.IntegrityError: duplicate key value violates unique constraint "unique_data_map_both_none"
它是否应该在第一个if form.is_valid():处检查约束
我错过了什么？