orm性能相关
-
尽量不查对象,能用values()
-
select_related('classes') 连表查询 多对一 一对一
-
prefetch_related('classes') 子查询 多对一 多对多
-
only('name') 指定某些字段 defer 指定排除某些字段
queryset 特性
多个数据库
配置
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
},
'db2': {
'ENGINE': 'django.db.backends.sqlite3',
'NAME': os.path.join(BASE_DIR, 'db2.sqlite3'),
},
}
迁移其他的数据库
python manage.py migrate --database db2
读写分离
手动
models.Student.objects.using('db2').all()
obj = models.Student.objects.using('db2').get(name='zhazha')
obj.name = 'star'
obj.save(using='default')
自动
settings配置:
DATABASE_ROUTERS = ['myrouter.Router']
class Router:
"""
读写分离
"""
def db_for_write(self, model, **kwargs):
return 'db2'
def db_for_read(self, model, **kwargs):
return 'default'
一主多从
class Router:
"""
一主多从
"""
def db_for_write(self, model, **kwargs):
return 'db1'
def db_for_read(self, model, **kwargs):
return random.choices['db2', 'db3', 'db4']
分库分表
class Router:
"""
分库分表
app01 model db1
app02 model db2
"""
def db_for_write(self, model, **kwargs):
app_name = model._meta.app_label
if app_name == 'app01':
return 'db1'
elif app_name == 'app02':
return 'db2'
def db_for_read(self, model, **kwargs):
app_name = model._meta.app_label
if app_name == 'app01':
return 'db1'
elif app_name == 'app02':
return 'db2'
django执行原生SQL的方法
# 1. extra
ret = models.Student.objects.all().extra(where=['id > %s'], params=['1'], order_by=['-id'])
# print(ret)
# for i in ret:
# print(i)
# 2. raw
ret = models.Student.objects.raw('select * from main.app01_classes where id <= 2')
print(ret)
for i in ret:
print(i.name)
# 3 connection
from django.db import connection, connections
# cursor = connection.cursor()
cursor = connections['db2'].cursor()
cursor.execute("""SELECT * from main.app01_classes where id > %s""", [1])
row = cursor.fetchall()
print(row)
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转载请注明:出处来自王晨曦个人站点 » django之ORM分库、读写分离、性能、原生sql补充
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