Cassandra乐观锁定 [英] Cassandra Optimistic Locking

问题描述

我有一个cassandra table1：

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。当我们从table1中读取一行时，我们记住它的version_num。当我们想更新这一行时，我们比较我们记住的当前version_num值和值。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. p>我们不能将version_num放在where子句中，这将创建一个错误：Bad Request：Non PRIMARY KEY version_num found where where clause：

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

因为我们需要更新其值

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

这个问题？

UPDATE。找到解决方案

找到解决方案：
Cassandra 2.0，轻量级交易
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;

我将收到一个带有[applied]列的行。此行包含布尔值：true =更新成功，false =在其他情况下。

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

推荐答案

2.0，轻量级交易 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

如果执行查询：

update table1 set version_num = 5其中name ='abc'if version_num = 4;
我将收到一个带有[applied]列的行。此行包含布尔值：true =更新成功，false =在其他情况下。

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