Django select related in raw request

Question

How to make \"manual\" select_related imitation to avoid undesirable DB hits?

we have:

class Country:
    name = CharField()
class City:
    country          


        

Answer 1

Not sure if you still need this, but I solved it starting with Alasdair's answer. You want to use the info from the query to build the model or it'll still fire additional queries when you try to access the foreign key field. So in your case, you'd want:

    cities = list(City.objects.raw("""
        SELECT
            city.*, country.name as countryName
        FROM
            cities INNER JOIN country ON city.country_id = country.id
        WHERE
            city.name = 'LONDON"""))
    for city in cities:
        city.country = Country(name=city.countryName)

The line that assigns the country doesn't hit the database, it's just creating a model. Then after that, when you access city.country it won't fire another database query.