扩展Nextdoor的数据库：第三部分
In this part of the Scaling Nextdoor’s Datastores blog series, we’ll explore how the Core-Services team at Nextdoor serializes database data for caching while ensuring forward and backward compatibility between the cache and application code.
在《Scaling Nextdoor的Datastores》博客系列的这一部分中，我们将探讨Nextdoor的核心服务团队如何序列化数据库数据以进行缓存，同时确保缓存与应用程序代码之间的前向和后向兼容性。
In part 1 of this series we discussed how ORMs, object-relational mapping frameworks, help abstract away database specific schemas and queries from application code. Developers simply utilize objects in their application’s language to access database data.
在本系列的第1部分中，我们讨论了ORM（对象关系映射）框架如何帮助将数据库特定的模式和查询从应用程序代码中抽象出来。开发人员只需在其应用程序的语言中使用对象来访问数据库数据。
Here’s a simple example of using Python’s Django ORM to define a model:
这是一个使用 Python 的 Django ORM 定义 模型 的简单示例：
from django.db import models
from django.db import models
class Users(models.Model):
class Users(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
The associated SQL create table would look like:
相关的SQL创建表语句如下：
CREATE TABLE users (
"id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
"first_name" varchar(30) NOT NULL,
"last_name" varchar(30) NOT NULL
);
CREATE TABLE users (
"id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
"first_name" varchar(30) NOT NULL,
"last_name" varchar(30) NOT NULL
);
Developers would then access database data like this:
开发者可以像这样访问数据库数据：
user_id = 123
user = User.objects.get(id=user_id)
print(user.first_name)
user_id = 123
user = User.objects.get(id=user_id)
print(user.first_name)
Object Byte Serialization for Caching
用于缓存的对象字节序列化
An issue arises when adding a look-aside cache such as Redis/Valkey to an application: How do you store what you got from the database in the cache?
在向应用程序添加像Redis/Valkey这样的旁路缓存时，会出现一个问题：如何将从数据库中获取的数据存储在缓存中？
A common solution to caching complex objects, such as those from ORMs, is object byte serialization. This ...