cassandra中列的默认排序顺序？ [英] default sorting order of columns in cassandra?

问题描述

我正在阅读本教程，其中讲师说连续的列的默认顺序为 UTF8-tye 。但是他不作进一步探讨。

I was going through the tutorial where the instructor says that the default ordering of columns with in a row is UTF8-tye. But he does not touch upon it further.

我不明白这是什么意思。特别是如果我的列是不同的类型，例如 int ， timestamp 等，会怎样？

I don't understand what it means. especially what if my columns are different types such as int, timestamp etc.

我还要如何将列的排序顺序指定为 UTF8类型以外的其他内容。

Also how would I specify the sort order on the columns to be something other than "UTF8-type".

推荐答案

他在谈论的是列名，而不是列值。
在旧的cassandra版本中，您可以使用SuperColumns，它们是行中列的集合。像这样的东西：

He is talking about the columns names, not the columns values. In old cassandra versions you could use SuperColumns, which are collections of columns within a Row. Something like this:

{ RowKey: 
   { SuperColumn1Key: {c1:v, c2:v .... } },
   { SuperColumn2Key: {c1:v, c2:v .... } },
   { SuperColumn3Key: {c1:v, c2:v .... } }
}

这与今天的情况很相似。比较器既可以建立行中的超级列排序，也可以根据名称对列进行排序（您可以在SuperColumnFamily中选择两个不同的比较器，一个用于超级列排序，另一个用于列排序）。例如，将TimeUUID比较器用于超级列，您可以按时间检索它们，而UTF8Type是字母排序。

It is something similar to what today is a wide row. The comparator could establish both the sorting of supercolumns within a row and also sorting of columns by their name (you could choose two differents comparator in a SuperColumnFamily, one for supercolumns sorting and another for columns sorting). For example using TimeUUID comparator for supercolumns you could retrieve them sorted by time while UTF8Type is an "alphabetic" sorting.

想象一下UTF8列比较器中的这一行：

Imagine this row in an UTF8 Columns Comparator:

{ id: {"author":"john", "vote": 3} }

现在让我们添加一个新列，说文字。由于是utf8，因此文字（ a << t> v）将位于作者和投票之间

Now let's add a new column, say text. Since it's utf8, "text" ("a"<"t"<"v") will be between author and vote

{ id: {"author":"john", "text": "blablabla", "vote": 3} }

不过，我认为您看到的是旧视频，因为在新版本中不再使用此概念

However I think what you've seen is an old video, since this concept is not used anymore in newer version

HTH，Carlo

HTH, Carlo

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