Django bulk_create()、update()与数据库事务的效率对比分析

# 用for循环挨个创建，共花费37秒
  for i in range(10000):
    name="String number %s"%i
    Record.objects.create(name=name)
 
# 用django事务只提交一次，共花费2.65秒
@transaction.commit_manually
def manual_transaction():
  for i in range(10000):
    name="String number %s"%i
    Record.objects.create(name=name)
  transaction.commit()
 
# 用bulk_create创建,共花费0.47秒
def builtin():
  insert_list =[]
  for i in range(10000):
    name="String number %s"%i
    insert_list.append(Record(name=name))
  Record.objects.bulk_create(insert_list)
 
# 用for循环挨个更新，共花费72秒:
def auto_transaction():
  for record inRecord.objects.all():
    record.name ="String without number"
    record.save()
 
# 用django事务只提交一次，共花费17秒
@transaction.commit_manually
def manual_transaction():
  for record inRecord.objects.all():
    record.name ="String without number"
    record.save()
  transaction.commit()
 
# 用update更新,共花费0.33秒
def builtin():
  Record.objects.all().update(name="String without number")

from django.db import models
from datetime import datetime

class User(models.Model):
  id = models.BigAutoField('主键', primary_key=True)
 
  name = models.CharField('名字', max_length=20, db_index=True, default='')
 
  create_time_one = models.DateTimeField('创建时间', default=datetime.now())
  update_time_one = models.DateTimeField('更新时间', default=datetime.now)
 
  create_time_tow = models.DateTimeField('创建时间', auto_now_add=True)
  update_time_tow = models.DateTimeField('更新时间', auto_now=True)

names = ['张三', '李四']
for name in names:
  user = User(name=name)
  user.save()
  print(user.id) # 此时user对象有id的值

names = ['张三', '李四']
users = [User(name=name) for name in names]
users = User.objects.bulk_create(users)
print([user.id for user in users]) # 此时user对象没有id的值

from django.db import models
from datetime import datetime
 
class User(models.Model):
  id = models.BigAutoField('主键', primary_key=True)
  name = models.CharField('名字', max_length=20, db_index=True, blank=False, default='')
  create_time = models.DateTimeField('创建时间', auto_now_add=True)
  update_time = models.DateTimeField('更新时间', default=datetime.now)

# 方法一
names = ['张三', '李四']
users = [User(name=name) for name in names]
users = User.objects.bulk_create(users)
 
# 方法二
names = ['张三', '李四']
users = [User(name=name) for name in names]
[user.save() for user in users]

# 方法一
names = ['张三', '李四']
User.objects.filter(name__in=names).update(name='changed', update_time=datetime.now()) # 这里必须显式对update_time赋值
 
# 方法二
names = ['张三', '李四']
users = User.objects.filter(name__in=names)
for use in users:
  user.name = 'changed'
  user.save() # 这里会自动更新update_time，但是多次save效率低