Cassandra alter column type：哪些类型兼容？ [英] Cassandra alter column type: which types are compatible?

问题描述

关于一些示例，当列类型不能更改时，有关网络的一些补丁信息。例如，在 DataStax网站有提及：

• 更改聚类列的类型。


• 更改定义了
  的列。

例如，此处提到您无法将 uuid 到 timeuuid 。根据我的个人经验，我不能将 text 更改为 timestamp （我们将日期以ISO8601格式存储为文本，一个不幸的决定在项目时间表的早期）。

但是，我找不到哪些类型可以转换到哪个类型的完整描述，或至少哪些类型不能转换为。有人知道吗？

解决方案

很好的问题！我不得不承认，我对这个缺乏详尽的文档有点惊讶，以及。您的问题启发了我做一个小调查和博客。 / p>

基本上，这里是Cassandra兼容的CQL类型的完整列表（使用Cassandra 2.2.0）

：

• ascii - > blob，text，varchar


• bigint - > blob ，timestamp，varint


• int - > blob，varint


• ，varchar


• timestamp - > bigint，blob，varint


• timeuuid - > blob ，UUID


• varchar - > blob，文字

：

• blob有很多，因为 可以转换成blob。


• cqlsh允许您将varint转换为新的日期类型，但这是一个错误（ CASSANDRA-10027 ）。不要尝试。

There's some patchy information on the interwebs about some examples when column type can't be changed. For example, on the DataStax site there's a mention:

• Changing the type of a clustering column.
• Changing columns on which an index is defined.

Or, for example, here is mentioned that you can't convert uuid to timeuuid. And from my personal experience, I can't change text to timestamp (we store dates in ISO8601 format as text, an unfortunate decision early in the project timeline).

However, I can't find a full description of which types can be converted to which, or at least which types can't be converted to which. Does anyone know?

解决方案

Great question! I have to admit that I was a bit surprised at the lack of thorough documentation on this one, as well. Your question inspired me to do a little investigation and blog about it as well.

Essentially, here is a comprehensive list of Cassandra compatible CQL types (using Cassandra 2.2.0):

• ascii -> blob, text, varchar
• bigint -> blob, timestamp, varint
• int -> blob, varint
• text -> blob, varchar
• timestamp -> bigint, blob, varint
• timeuuid -> blob, UUID
• varchar -> blob, text

Notes:

• blob is in there a lot, because anything can be converted to a blob.
• cqlsh allows you to convert a varint to the new date type, but this is a bug (CASSANDRA-10027). Don't actually try that.

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