CQL3 每行都有自己的架构 [英] CQL3 Each row to have its own schema

问题描述

我想在 .Net 应用程序中使用 Cassandra.我的目标是将一些数据存储在一个列族中，但每一行数据都有不同的架构.

I want to use Cassandra in a .Net application. My objective is to store some data in a column family, but each row of data will have varying schema.

示例(一个非常简单的示例)我想要一个玩具"列族来存储以下对象，(注意它们除了 ID 属性之外还有非常不同的属性)

Example (A very simple one) I want to have a 'Toys' column family to store the following objects, (Notice how they have very different properties other than the ID property)

玩具对象 1{id":1"，"name":"汽车","number_of_doors":4,喜欢":3}

Toy object 1 { "id":"1", "name":"Car", "number_of_doors":4, "likes":3}

玩具对象 2{id":2"，"type":"飞机","flying_range":"100m"}

Toy object 2 { "id":"2", "type":"Plane", "flying_range":"100m"}

玩具对象 3{id":3"，"类别":"火车","number_of_carriages":10}

Toy object 3 { "id":"3", "category":"Train", "number_of_carriages":10}

从我对 Datastax CSharp 驱动程序的初步理解和使用来看，我必须始终更改不适合我的表(列族).我希望每一行都有自己的架构.Thrift API 或许可以解决这个问题，但 HectorSharp 似乎已经死了.

From my initial understanding and using of Datastax CSharp driver I have to always alter the table (Column family) which does not sit right with me. I would like each row to have its own schema. Thrift API might be able to solve this but it seems HectorSharp is all but dead.

与我的要求类似的问题，但没有我想要的答案

A question similar to my requirement but it doesn't have the answer I want

Cassandra对于无模式数据库，每天有数百万个订单表和数百万次查询

我是否期望每一行都有自己的架构，或者有没有办法使用 Cassandra+Csharp 来做到这一点?

Am I barking up the wrong tree by expecting each row to have its own schema or is there a way to do this using Cassandra+Csharp ?

预先感谢您的回答.

推荐答案

Cassandra 的旧版本是无模式的，这意味着您没有任何地方可以定义行可以包含的内容.您现在需要的可以部分在 Cassandra 2.1

Older versions of Cassandra were Schema-less, meaning that you didn't have anywhere a definition of what a row could contain. What you need now could be partially done with a Map on Cassandra 2.1

CREATE TABLE toys (
    id text PRIMARY KEY,
    toy map<text, text>
)

放一些数据...

INSERT INTO toys (id, toy) VALUES ( '1', {'name':'Car', 'number_of_doors':'4', 'likes':'3'});
INSERT INTO toys (id, toy) VALUES ( '2', {'type':'Plane', 'flying_range':'100m'});
INSERT INTO toys (id, toy) VALUES ( '3', {'category':'Train', 'number_of_carriages':'10'});

表格内容...

 id | toy
----+-------------------------------------------------------
  3 |    {'category': 'Train', 'number_of_carriages': '10'}
  2 |             {'flying_range': '100m', 'type': 'Plane'}
  1 | {'likes': '3', 'name': 'Car', 'number_of_doors': '4'}

我们现在可以在键上创建索引...

We can now create an index on keys ...

CREATE INDEX toy_idx ON toys (KEYS(toy));

... 并对 Map 键执行查询...

... and perform queries on Map keys ...

SELECT * FROM toys WHERE toy CONTAINS KEY 'name';

 id | toy
----+-------------------------------------------------------
  1 | {'likes': '3', 'name': 'Car', 'number_of_doors': '4'}

现在您可以像处理普通列一样更新或删除地图条目，而无需在写入前阅读

Now you can update or delete map entries like you would do with normal columns, without reading before writing

DELETE toy['name'] FROM toys WHERE id='1';
UPDATE toys set toy = toy + {'name': 'anewcar'} WHERE id = '1';
SELECT * FROM toys;

 id | toy
----+-----------------------------------------------------------
  3 |        {'category': 'Train', 'number_of_carriages': '10'}
  2 |                 {'flying_range': '100m', 'type': 'Plane'}
  1 | {'likes': '3', 'name': 'anewcar', 'number_of_doors': '4'}

一些限制

1. 您无法检索集合的一部分:即使在内部将地图的每个条目存储为一列，您也只能检索整个集合
2. 您必须选择是在键上还是在值上同时创建索引不支持.
3. 因为地图是输入的，所以你不能输入混合值——在我的例子中，所有整数现在都是字符串

我个人认为这种方法的广泛使用是一种反模式.

I personally consider an extensive usage of this approach an anti-pattern.

HTH，卡罗

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