November 2021
Beginner to intermediate
239 pages
4h 15m
Chinese
Content preview from Dapr学习手册
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
102
｜
第
2
章
要获得相关联的
ETag
，使用这个
:
HGET myapp||balance version
2.5.2 Azure Cosmos DB
Azure Cosmos DB
是一个全球分布式、多模型数据库服务。它支持用多种
流行的
API
对同一数据集进行操作，包括
SQL
、
MongoDB
、
Cassandra
、
Gremlin
等。
Dapr
使用
Cosmos DB
的
SQL API
来保存状态数据。
Cosmos DB
状态存储配
置为
Cosmos DB
数据库上的特定集合。要使用多个集合，你需要为每个集合
定义一个单独的状态存储。
要查询与
Dapr ID myapp
相关联的所有状态，使用这个
SQL
查询（假设
Cosmos DB
集合被命名为
states
）：
SELECT * FROM states WHERE CONTAINS(states.id, 'myapp||')
要从名为
balance
的特定
key
中获取数据，请使用以下查询。
SELECT * FROM states WHERE states.id = 'myapp||balance'
要获得
ETag
，请使用系统
_etag
列。
SELECT states._etag FROM states WHERE states.id ='myapp||balance'
也可以使用
Cosmos DB
的聚合功能来执行更高级的查询。例如，下面的查询
计算
states
集合中所有值的总和（假设数据保存在
value
字段中）。
SELECT VALUE ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.