About Many-to-many Relationships to Self
In Django, Many-to-many relationships to self are symmetrical by default and create two database entries for each relation.
class Location(models.Model):
name = models.CharField(max_length=200)
related_locations = models.ManyToManyField("self", blank=True)
This means, that these would work out of the box:
location1.related_locations.filter(pk=location2.pk).exists()
location2.related_locations.filter(pk=location1.pk).exists()
And both location1 and location2 would be in the following query:
locations_with_related_locations = Location.objects.annotate(
related_locations_count=models.Count("related_locations"),
).filter(related_locations_count__gt=0)
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