Hoe om te gaan met een verouderde database in het Django-framework

U kunt enkele methoden toevoegen aan oudere modellen om gerelateerde items wat efficiënter op te halen:

class Listflower(models.Model):
    especies_id = models.AutoField(primary_key=True)
    family_id = models.IntegerField(blank=True, null=True)
    especies = models.CharField(max_length=255, blank=True, null=True)
    

    class Meta:
        managed = False
        db_table = 'listflower'

    def get_family(self):
        return FamilyModel.objects.get(family_id=self.family_id)


class Estate(models.Model):
    estate_id = models.AutoField(primary_key=True)
    estate_name = models.CharField(max_length=100, blank=True, null=True)
 

    class Meta:
        managed = False
        db_table = 'estates'

    def get_flowers(self):
        flower_ids = Flower2Estate.objects.filter(estate_id=self.estate_id).values_list('especies_id', flat=True)
        return Listflower.objects.filter(especies_id__in=flower_ids)

Maar als het niet de laatste keer is dat u met deze gegevens werkt, is het waarschijnlijk de beste manier om reguliere django-modellen met fks te definiëren en eenmaal een script te schrijven om oude gegevens naar een nieuwe modelstructuur te converteren. De uitdaging zou niet langer dan een uur moeten duren.

UPDATE

class FlowerFamily(models.Model):
    # assuming you old family model has 
    # "family_id" and "family_name" fields
    family_id = models.IntegerField(blank=True, null=True)
    family_name = models.CharField(max_length=255, blank=True, null=True)


class Flower(models.Model):
    # you might want preserve old model fields in the new model
    # at least id fields
    especies_id = models.IntegerField(blank=True, null=True)
    family_id = models.IntegerField(blank=True, null=True)
    especies = models.CharField(max_length=255, blank=True, null=True)

    family = models.ForegnKey(FlowerFamily, related_name='flowers')


class NewEstate(models.Model):
    estate_id = models.IntegerField(blank=True, null=True)
    estate_name = models.CharField(max_length=100, blank=True, null=True)
    flowers = models.ManyToManyField(Flower, related_name='estates')




# this is a slightly primitive example
# in real life you might want to use get_or_create instead of direct creation 
# in case script fails and you'll need to run it again
# also objects.get() might better be used with try-except ObjectDoesNotExist
def convert_legacy():
    # create new instances
    for ff in YourOldFamilyModel.objects.all():
        new_ff = FlowerFamily(family_id=ff.family_id, family_name=ff.family_name)
        new_ff.save()

    for fl in Listflower.objects.all():
        new_fl = Flower(...)

        family = FlowerFamily.objects.get(family_id=fl.family_id)

        new_fl.family = family
        new_fl.save()
    
    # same thing for Estate
    for ...:
        new_estate ...
        new_estate.save()

        # and restore relations
        flower_ids = Flower2Estate.objects.filter(estate_id=new_estate.estate_id).values_list('especies_id', flat=True)

        for new_lf in Flower.objects.filter(especies_id__in=flower_ids):
            new_estate.flowers.add(new_fl)