[밥 먹언] ORM 최적화

🎉🎉🎉 ORM 단축 성공

localhost:8000/places/search?region=1&date=2022-07-12

before

-------------------------------------------------------------------
Function : get
Number of Queries : 170
Finished in : 0.15s
-------------------------------------------------------------------

after

-------------------------------------------------------------------
Function : get
Number of Queries : 22
Finished in : 0.06s
-------------------------------------------------------------------

실습 🖥

models.py

from django.db import models

class Place(models.Model):
    name                         = models.CharField(max_length=100)
    address                      = models.CharField(max_length=200)
    phone_number                 = models.CharField(max_length=50, default='')
    opening_hours                = models.CharField(max_length=200, default='')
    description                  = models.CharField(max_length=1000, default='')
    maximum_number_of_subscriber = models.IntegerField()
    latitude                     = models.DecimalField(max_digits=11, decimal_places=8)
    longitude                    = models.DecimalField(max_digits=11, decimal_places=8)
    able_to_reserve              = models.BooleanField()
    closed_temporarily           = models.BooleanField()
    category                     = models.ForeignKey('Category', on_delete=models.CASCADE)
    region                       = models.ForeignKey('Region', on_delete=models.CASCADE)
    menus                        = models.ManyToManyField('Menu', through='PlaceMenu', related_name='places')

    class Meta:
        db_table = 'places'

class PlaceMenu(models.Model):
    menu          = models.ForeignKey('Menu', on_delete=models.CASCADE)
    place         = models.ForeignKey('Place', on_delete=models.CASCADE)
    price         = models.ForeignKey('Price', on_delete=models.CASCADE)
    is_signature  = models.BooleanField()

    class Meta:
        db_table = 'places_menus'

class Menu(models.Model):
    name = models.CharField(max_length=50)

    class Meta:
        db_table = 'menus'

class Price(models.Model):
    price = models.DecimalField(max_digits=7, decimal_places=0)

    class Meta:
        db_table = 'prices'

class Category(models.Model):
    name  = models.CharField(max_length=50)

    class Meta:
        db_table = 'categories'

class Image(models.Model):
    image_url  = models.CharField(max_length=1000)
    place      = models.ForeignKey('Place', on_delete=models.CASCADE)

    class Meta:
        db_table = 'images'

class Region(models.Model):
    name  = models.CharField(max_length=50)

    class Meta:
        db_table = 'regions'

select_related 적용

  places = Place.objects.select_related('category', 'region').~~~

prefetch_related 적용

Place.objects.prefetch_related('placemenu_set__price', 'menus', 'image_set') ~~~

decorators.py

import functools, time
from django.db   import connection, reset_queries
from django.conf import settings

def query_debugger(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        reset_queries()
        number_of_start_queries = len(connection.queries)
        start  = time.perf_counter()
        result = func(*args, **kwargs)
        end    = time.perf_counter()
        number_of_end_queries = len(connection.queries) - 2 if len(connection.queries) else 0
        print(f"-------------------------------------------------------------------")
        print(f"Function : {func.__name__}")
        print(f"Number of Queries : {number_of_end_queries-number_of_start_queries}")
        print(f"Finished in : {(end - start):.2f}s")
        print(f"-------------------------------------------------------------------")
        return result
    return wrapper

-------------------------------------------------------------------
Function : get
Number of Queries : 170
Finished in : 0.15s
-------------------------------------------------------------------

1. select_related 적용 후

-------------------------------------------------------------------
Function : get
Number of Queries : 137
Finished in : 0.11s
-------------------------------------------------------------------

2. prefetch_related 적용 후

-------------------------------------------------------------------
Function : get
Number of Queries : 56
Finished in : 0.08s
-------------------------------------------------------------------

3. select_related, prefetch_related 적용 후

-------------------------------------------------------------------
Function : get
Number of Queries : 22
Finished in : 0.06s
-------------------------------------------------------------------