Cassandra 乐观锁 [英] Cassandra Optimistic Locking

问题描述

我有一个 cassandra 表 1:

I have a cassandra table1:

CREATE TABLE Policy.table1 (
name VARCHAR ,
date TIMESTAMP ,
version_num INT,
PRIMARY KEY   (
         name
         )) WITH caching = 'all'
     --   and memtable_flush_period_in_ms = 7200 ;
     ;

我需要在 tis 表上实现乐观锁定.当我们从 table1 中读取一行时，我们会记住它的 version_num.当我们想要更新这一行时，我们会比较当前的 version_num 值和我们记住的值.此外，我们需要在每次更新时增加 version_num.

I need to implement optimistic locking on tis table. When we read a row from table1 we remember its version_num. And when we want to update this row we compare current version_num value and value that we remembered. Also we need to increment version_num on each update.

问题:

1. 我们不能将 version_num 放入 where 子句中，这会产生错误:Bad Request: Non PRIMARY KEY version_num found in where 子句:

1. We cannot put version_num into where clause, this will create an error: Bad Request: Non PRIMARY KEY version_num found in where clause:

 update table where name = 'abc' and version = 3

我们不能将version_num设置为主键的一部分，因为我们需要更新它的值

We cannot set version_num as a part of primary key, because we need to update its value

您认为此问题有什么解决方案吗?

Do you see any solution for this problem?

推荐答案

在那里找到了解决方案:Cassandra 2.0，轻量级事务 http://www.datastax.com/documentation/cassandra/2.0/cassandra/dml/dml_ltwt_transaction_c.html

The solution was found there: Cassandra 2.0, Lightweight transactions http://www.datastax.com/documentation/cassandra/2.0/cassandra/dml/dml_ltwt_transaction_c.html

如果我执行查询:

update table1 set version_num = 5 where name = 'abc'  if version_num = 4;

我将收到带有 [applied] 列的行.此行包含布尔值:true = 更新成功，false = 其他情况.

I will receive a row with [applied] column. This row contains boolean value: true = update was successful, false = in other case.

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