Re: Flattening model relationships (in APIs)

Hey Mike,

Thanks for your thoughts. Perhaps I presented my requirement incorrectly. I don't at all want to denormalize the database. My point was that because of the way models are related, I'm ending up with city containing state containing country. This, I feel, would be a chore for the front-end guys. So my question is, how can I rearrange these fields to give a flat JSON output rather than have objects within objects. I hope it makes more sense now.

~~ Ankush

On Wednesday, February 22, 2017 at 9:59:26 AM UTC+5:30, Mike Dewhirst wrote:

Ankush

I think you might have to provide more than one method for retrieving an
address so applications can request particular subsets. Perhaps a
local-postal address, international-postal address, geo-location,
what-three-words address and of course the full bucket as required.

I think it is always best to normalize as much as possible in the
beginning and de-normalize only if performance becomes an issue.

Also ...

https://hackernoon.com/10-things-i-learned-making-the-fastest-site-in-the-world-18a0e1cdf4a7#.3l8n34dvk

Mike

On 22/02/2017 6:09 AM, Ankush Thakur wrote:
> I'm using DRF for an API. My problem is that I defined my postal
> address like this (breaking it up into City, State, Country):
>
> class Country(models.Model):
>     class Meta:
>         db_table = 'countries'
>
>     name = models.TextField()
>     code = models.TextField(unique=True)
>
> class State(models.Model):
>     class Meta:
>         db_table = 'states'
>
>     name = models.TextField()
>     code = models.TextField(unique=True)
>     country = models.ForeignKey('Country', on_delete=models.CASCADE)
>
>
> class City(models.Model):
>     class Meta:
>         db_table = 'cities'
>
>     name = models.TextField()
>     code = models.TextField(unique=True)
>     state = models.ForeignKey('State', on_delete=models.CASCADE)
>
> class Address(models.Model):
>     class Meta:
>         db_table = 'addresses'
>     building_no = models.TextField()
>     street = models.TextField(null=True)
>     locality = models.TextField(null=True)
>     landmark = models.TextField(null=True)
>     pincode = models.TextField(null=True)
>     latitude = models.DecimalField(max_digits=9, decimal_places=6,
> null=True)
>     longitude = models.DecimalField(max_digits=9, decimal_places=6,
> null=True)
>     city = models.ForeignKey('City', on_delete=models.CASCADE)
>
> Now, in my system, a venue has an address, and so the serializes are
> defined like this:
>
> class VenueSerializer(serializers.ModelSerializer):
>     address = AddressSerializer()
>     offerings = OfferingSerializer(many=True)
>
>     class Meta:
>         model = Venue
>         fields = ['id', 'name', 'price_per_day', 'status',
> 'offerings', 'address', 'photos']
>
> which leads us to:
>
> class AddressSerializer(serializers.ModelSerializer):
>     city = CitySerializer()
>
>     class Meta:
>         model = Address
>         fields = ['id', 'building_no', 'street', 'locality',
> 'landmark', 'pincode', 'latitude', 'longitude', 'city']
>
> which leads us to:
>
> class CitySerializer(serializers.ModelSerializer):
>     state = StateSerializer()
>
>     class Meta:
>         model = City
>         fields = ['id', 'name', 'code', 'state']
>
> which leads us to:
>
> class StateSerializer(serializers.ModelSerializer):
>     country = CountrySerializer()
>
>     class Meta:
>         model = State
>         fields = ['id', 'name', 'code', 'country']
>
> which finally leads to:
>
> class CountrySerializer(serializers.ModelSerializer):
>     class Meta:
>         model = Country
>         fields = ['id', 'name', 'code']
>
> and when this gets serialized, the address is given in the following
> format:
>
>  "address": {
>       "id": 2,
>       "building_no": "11",
>       "street": "Another Street",
>       "locality": "",
>       "landmark": "Fortis Hospital",
>       "pincode": "201003",
>       "latitude": "28.632778",
>       "longitude": "77.219722",
>       "city": {
>         "id": 1,
>         "name": "Delhi",
>         "code": "DEL",
>         "state": {
>           "id": 1,
>           "name": "Delhi",
>           "code": "DEL",
>           "country": {
>             "id": 1,
>             "name": "India",
>             "code": "IN"
>           }
>         }
>       }
>     }
>
> So there's a hell lot of nesting from city to state to country. If the
> relationship chain was even deeper, there would be even more nesting,
> which I feel isn't great for API consumers. What is the best practice
> here to put state and country at the same level as the city? I think
> this will also complicate the logic while POSTing data, so I'm
> interested in knowing about that as well.
>
> I'm sorry if there is too much code, but I couldn't think of a better
> way to convey the situation than actually post everything.
>
>
> Regards,
> Ankush Thakur
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