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django-prefetch_related
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# -*- coding: utf-8 -*- | |
from django.db import models | |
class Person(models.Model): | |
name = models.CharField(max_length=128) | |
class Group(models.Model): | |
name = models.CharField(max_length=128) | |
members = models.ManyToManyField(Person, through='Membership') | |
class Membership(models.Model): | |
person = models.ForeignKey(Person, on_delete=models.CASCADE) | |
group = models.ForeignKey("Group", on_delete=models.CASCADE) | |
date_joined = models.DateField() | |
invite_reason = models.CharField(max_length=64) | |
""" | |
Shell | |
In [13]: gs = list(Group.objects.all().prefetch_related('members')) | |
SELECT `app_group`.`id`, | |
`app_group`.`name` | |
FROM `app_group` | |
Execution time: 0.006087s [Database: default] | |
SELECT (`app_membership`.`group_id`) AS `_prefetch_related_val_group_id`, | |
`app_person`.`id`, | |
`app_person`.`name`, | |
`app_person`.`company_id` | |
FROM `app_person` | |
INNER JOIN `app_membership` | |
ON (`app_person`.`id` = `app_membership`.`person_id`) | |
WHERE `app_membership`.`group_id` IN (1, 2) | |
Execution time: 0.006120s [Database: default] | |
In [14]: gs | |
Out[14]: [<Group: Group object (1)>, <Group: Group object (2)>] | |
In [15]: g = gs[0] | |
In [16]: g.members | |
Out[16]: <django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager at 0x109742520> | |
In [17]: g.members.all() | |
Out[17]: <QuerySet [<Person: Person object (5)>, <Person: Person object (6)>]> | |
""" |
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@gghotted
장고에서
django.db.backends
로거 표준 출력하면 쿼리랑 실행시간이 표시됩니다.