KimSoungRyoul

from datetime import datetime

from django.contrib.auth.models import User
from django.db import models


class Company(models.Model):
    name: str = models.CharField(max_length=128, null=False)
    tel_num: str = models.CharField(max_length=128, null=False)
    address: str = models.CharField(max_length=128, null=False)

KimSoungRyoul

# app_name.management.commands.bulk_create.py를 만들고 이 내용을 bulk_create.py에 복붙하세요
from random import randint

from django.core.management import BaseCommand

from django.contrib.auth.hashers import make_password
from django.contrib.auth.models import User
from django.utils import timezone

KimSoungRyoul

python manage.py bulk_create --user_cnt 300 --company_cnt 100 --product_cnt 1000 --order_cnt 10000

KimSoungRyoul

# 1-1 이 QuerySet은 select_related()사용하지 않았어도 
# 필요한 조건을 inner join으로 해결하고 있다
# ORM이 이렇게 똑똑합니다...
(OrderedProduct.objects
 .filter(id=1, related_order__descriptions='sdfsdf')
 #.select_related('related_order'))
"""
SELECT *
    FROM "orm_practice_app_orderedproduct" 
    INNER JOIN "orm_practice_app_order" 

KimSoungRyoul

SELECT *,
       (select "descriptions"
            from orm_practice_app_order
            where  "orm_practice_app_orderedproduct"."related_order_id" = "orm_practice_app_order"."id"
             AND "descriptions" = '주문의 상세내용입니다...1') as descriptions
FROM "orm_practice_app_orderedproduct"
         WHERE  "orm_practice_app_orderedproduct"."id" = 1

KimSoungRyoul

(Model.objects
  .filter(조건절)
  .select_related('정방향_참조_필드')   # 해당 필드를 join해서 가져온다.
  .prefetch_related('역방향_참조_필드') # 해당 필드는 추가쿼리로 가져온다.
)

KimSoungRyoul

select * from 'Model' m
(inner OR left outer) join '정방향_참조_필드' r on m.r_id=r.id 
'where '조건절';

select * from '역방향_참조_필드' where id in ('첫번째 쿼리 결과의 id 리스트');

KimSoungRyoul

  # 1-2 이 쿼리는 prefetch_related를 사용했음에도 불구하고 
  # QuerySet이 추가적인 쿼리가 불필요하다 판단하여 inner join 전략을 택한다. 
  # 이 경우 .prefetch_related('related_order')는 무시된다
  (OrderedProduct.objects
    .filter(Q(product_cnt=30) & Q(related_order__descriptions='asdf'))
    .prefetch_related('related_order'))
    """
     SELECT * 
     FROM "orm_practice_app_orderedproduct" 
     INNER JOIN "orm_practice_app_order" ON ("orm_practice_app_orderedproduct"."related_order_id" = "orm_practice_app_order"."id") 

KimSoungRyoul

# 1-3 이 쿼리는 의도한대로 +1개의 쿼리로 related_order를 조회한다 
# filter절에서 related_order에 대해 별다른 내용이 없어서 반항없이 개발자의 의도대로 따라준다.
OrderedProduct.objects.filter(product_cnt=30).prefetch_related('related_order')
"""
    SELECT * 
    FROM "orm_practice_app_orderedproduct"
     WHERE "orm_practice_app_orderedproduct"."product_cnt" = 30;

    SELECT * 
     FROM "orm_practice_app_order" 

KimSoungRyoul

SELECT `orm_practice_app_company`.`id`,
        `orm_practice_app_company`.`name`,
        `orm_practice_app_company`.`tel_num`,
        `orm_practice_app_company`.`address`
  FROM `orm_practice_app_company`
  WHERE `orm_practice_app_company`.`name` = 'company_name1';
      

SELECT "orm_practice_app_product"."id", "orm_practice_app_product"."name", "orm_practice_app_product"."price", "orm_practice_app_product"."product_owned_company_id"
    FROM "orm_practice_app_product"