缓慢保存到 Django 数据库

Question

我创建了一个自定义 manage.py 命令，如下所示：

from django.contrib.auth.models import User
from django.core.management.base import BaseCommand
from photos.models import Person


class Command(BaseCommand):
    help = 'Pre-populate database with initial data'

    def _create_people(self, user):
        for i in range(0, 100):
            person = Person(first_name='FN', surname='SN', added_by=user)
            person.save()

    def handle(self, *args, **options):
        user = User.objects.get(username="user1")
        self._create_people(user)

我已经为 handle() 执行计时，如果我不执行 person.save() 大约需要 0.02 秒，如果我保存则每个 Person 大约需要 0.1 秒。数据库是 sqlite，我相信它应该更快。什么可以解释如此糟糕的表现，我该如何改进？

Answer 1

分析：

def _create_people(self, user):
   for i in range(0, 100):
     person = Person(first_name='FN', surname='SN', added_by=user)
     # Hits the database for each save.
     person.save()

此函数将访问数据库 100 次并每次自动提交，这就是导致性能低下的原因（不考虑 sqlite 与 MySQL 或 PostgreSQL 相比的低性能）。

改进：

在您的案例中，您需要的是 bulk_create，它将使用 class 构造函数 创建的对象数组作为输入。所以一个可能的解决方案如下：

def _create_people(self, user):
   person_data = {"first_name": "FN", "surname":"SN", "added_by": user}
   person_list = [Person(**person_data) for i in range(100)]
   Person.objects.bulk_create(person_list)

By default bulk_create hits the DB once no matter how many objects, except in SQLite (In SQLite it's about 999 per query.). How many objects can be created in a single query can be specified through the parameter batch_size.

注意：

save() will not be called, and the related signals will not be sent.

does not work with m2m relationships.

缓慢保存到 Django 数据库

Slow saving to Django database

python

sqlite

django

performance

django-queryset