Cassandra：什么是子列
http://wiki.apache.org/cassandra/CassandraLimitations
引用： Cassandra 有两级索引：键索引和列索引。但在超级列族中还有第三级子列；这些没有索引，并且对子列的任何请求都会反序列化该超级列中的所有子列。因此，您希望避免需要大量子列的数据模型。
=> 子列到底是什么？有趣的是，谷歌搜索这个词并没有真正产生结果。我知道超列的概念，但不太清楚术语“子列”到底指什么（如何定义）：
什么概念是正确的？
第一：
ROW-KEY
SubCol SubCol
col col col val
val val col val
或
第二：
ROW-KEY
Column Column
SubCol SubCol SubCol SubCol
val val val val
此外，定义中的内容是什么：
comparator = UTF8Type and
subcomparator = UTF8Type and
这只是定义的问题。
谢谢 马库斯
http://wiki.apache.org/cassandra/CassandraLimitations
Quote:
Cassandra has two levels of indexes: key and column. But in super columnfamilies there is a third level of subcolumns; these are not indexed, and any request for a subcolumn deserializes all the subcolumns in that supercolumn. So you want to avoid a data model that requires large numbers of subcolumns.
=>What is exactly the subcolumn? It's interesting, googling the term does nor really yield in results. I know the concepts of supercolumn, but its not really clear what exactly the term "subcolumn" refers to (how it is defined):
What concept is correct?
First:
ROW-KEY
SubCol SubCol
col col col val
val val col val
OR
Second:
ROW-KEY
Column Column
SubCol SubCol SubCol SubCol
val val val val
Furthermore, what is what in the Definitions:
comparator = UTF8Type and
subcomparator = UTF8Type and
Its only a matter of definition.
Thanks
Markus
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标准列的父级是其行。子列的父列是其超级列。除此之外，它们是相同的 - 只是有一个额外的嵌套级别，尽管正如您提到的那样对索引和检索有影响。
更多信息请访问 http://wiki.apache.org/cassandra/DataModel 和 http://arin.me/blog/wtf-is-a-supercolumn-cassandra-data-model
普通列族：
超级列族：
A standard column's parent is its row. A sub-column's parent is its supercolumn. Apart from that, they are the same - there's just an additional level of nesting, though there are implications for indexing and retrieval as you've mentioned.
More info at http://wiki.apache.org/cassandra/DataModel and http://arin.me/blog/wtf-is-a-supercolumn-cassandra-data-model
Normal column family:
Super column family:
comparator值指示列在查询中返回给您时将如何排序。相同的概念适用于子比较器，但适用于超级列。UTF8Type指的是字符的 Unicode 标准。The
comparatorvalue indicates how columns will be sorted when they are returned to you in a query. The same concept applies tosubcomparator, but for super columns.UTF8Typerefers to the Unicode standards for characters.