当我们使用IF NOT EXIST时，LWT-轻量级交易如何工作? [英] How the LWT- Light Weight Transaction is working when we use IF NOT EXIST?

问题描述

问题是，当我们使用

    INSERT INTO USERS (login, email, name, login_count)        
    values ('jbellis', '[e-mail]', 'Jonathan Ellis', 1)        
    IF NOT EXISTS    

如果不存在中的

确切地将哪些列进行了比较?主键(分区键+集群键)?还是只是分区键?

in IF NOT EXIST exactly which columns are compared together? primary key(partition-key + clustering-key)? or just partition-key?

推荐答案

以下是LWT的四个阶段的示意图:

Here is a diagram of the 4 phases of LWT: http://www.slideshare.net/doanduyhai/cassandra-introduction-nantesjug/89

原始博客文章在这里: http://www.datastax.com/dev/blog/lightweight-transactions-in-cassandra-2-0

The original blog post is here: http://www.datastax.com/dev/blog/lightweight-transactions-in-cassandra-2-0

究竟哪几列比较在一起?首要的关键?分区键?

exactly which columns are compare together? primary key? partition-key?

整个主键都在磁盘上检查.在示例中，它是一个简单的主键，因此它也是分区键，例如登录列

The whole primary key is checked on disk. In the example it is a simple primary key so it's also the partition key, e.g. login column

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