django admin - subquery inside list_filter

Question

Given are the following models

class Report(models.Model):
    id = models.CharField(max_length=256, unique=True)
    name = models.CharField(max_length=256)
    confidential = models.BooleanField(default=False)

class Owner(models.Model):
    first_name = models.CharField(max_length=512)
    last_name = models.CharField(max_length=512)
    title = models.CharField(max_length=512)
    birth_date = models.CharField(max_length=512)
    company = models.CharField(max_length=512)
    address = models.CharField(max_length=512)
    city = models.CharField(max_length=512)
    last_login = models.DateTimeField(auto_now=True)
    access_granted = models.DateTimeField(auto_now_add=True)
    report = models.ForeignKey(Report, on_delete=models.CASCADE)

and the following admin.py from django

class OwnerAdmin(admin.ModelAdmin):
    .
    .
    .
    list_filter = ('report__name',)

As expected I get the option to filter based on the name of the report. Yet I would like to only get displayed to filter if the report is confidential, means that the confidential field of the given report is true. How can i achieve this?

Answer 1

If I am understanding your question correctly, you would like to only list the confidential reports in your list_filter. To do this you will need to create a custom filter:

class ReportListFilter(admin.SimpleListFilter):

    title = 'Confidential Reports'
    parameter_name = 'confidential_reports'

    def lookups(self, request, model_admin):
        confidential_reports = Report.objects.filter(confidential=True)
        return tuple(
            (report.id, report.name) for report in confidential_reports
        )

    def queryset(self, request, queryset):
        if self.value()
            return queryset.filter(report_id=self.value())
        return queryset.all()

To understand the above, you can read more about it in the docs, but a summary is that:

• title: gives the title for your filter
• parameter_name: gives the string that will be used in the URL when your filter is used
• lookups returns a list of tuples that gives the values for the filter
• queryset is what does the actual filtering.

Then you just need to add it into your OwnerAdmin and everything should work:

class OwnerAdmin(admin.ModelAdmin):
    .
    .
    .
    list_filter = (ReportListFilter,)