Dry ORM

Code

Result

no cache

from django.db import models
from django.db.models import Prefetch, Q

class Network(models.Model):
    code = models.CharField(max_length=8)
    
    def __str__(self) -> str:
        return self.code

class Station(models.Model):
    code = models.CharField(max_length=8)
    network = models.ForeignKey(Network, on_delete=models.PROTECT)
    
    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=["code", "network"], name="station_code_network_id_unique"
            )
        ]

def __str__(self) -> str:
        return self.code
    
def run():
    net1 = Network.objects.create(code="net1")
    net2 = Network.objects.create(code="net2")
    stat1 = Station.objects.create(
        network=net1, code="stat1",
    )
    stat25 = Station.objects.create(
        network=net2, code="stat25",
    )
    networks = list(
        Network.objects.filter(code="net1").prefetch_related(
            Prefetch(
                "station_set",
                queryset=Station.objects.filter(code="stat1")
            )
        ).union(
            Network.objects.filter(code="net2").prefetch_related(
                Prefetch(
                    "station_set",
                    queryset=Station.objects.filter(code="stat25")
                )
            )
        )
    )
    print("with custom prefetch")
    print(networks[0].station_set.all())
    print(networks[1].station_set.all())
    networks = list(
        Network.objects.filter(code="net1").prefetch_related("station_set").union(
        Network.objects.filter(code="net2").prefetch_related("station_set")
    ))
    print("with regular prefetch")
    print(networks[0].station_set.all())
    print(networks[1].station_set.all())

Output

No output.

Queries

TCLTCL DDLDDL SELECTS INSERTI UPDATEU DELETED REVERSER

QueriesQ (0)

No queries.