如何使用CQL更新Cassandra整数列? [英] How do you update a Cassandra integer column using CQL?

问题描述

我在Cassandra中有一个表格评论"，如下所述:

I have a table 'reviews' in Cassandra as mentioned below:

CREATE TABLE reviews (
  review_id text,
  downcount int,
  upcount int,
  creation_date timestamp,
  PRIMARY KEY (review_id)
)

让我们说我想将 upcount 值增加1，如何在Cassandra CQL中做到这一点?

Lets say I want to increase the upcount value by 1, how can I do that in Cassandra CQL?

当我这样做时:

UPDATE reviews SET upcount = upcount +1 WHERE review_id = '123456';

它给了我以下错误:

错误请求:对非计数器列 upcount 无效的操作( upcount = upcount + 1 ).

推荐答案

您可以使用Cassandra的计数器列数据类型.请记住，如果非计数器列不属于复合 PRIMARY KEY 的一部分，则不能将计数器列与同一列族中的非计数器列混合使用.因此，您必须将计数器分成另一个列族，例如 reviews_counts .

You can use Cassandra's counter columns data type. Keep in mind you cannot mix counter columns with non-counter columns in the same column family if the non-counter columns are not part of the composite PRIMARY KEY. So you have to separate the counters into another column family, say reviews_counts.

CREATE TABLE reviews (
  review_id text,
  creation_date timestamp,
  PRIMARY KEY (review_id)
)

CREATE TABLE reviews_counts (
  review_id text,
  downcount counter,
  upcount counter,
  PRIMARY KEY (review_id)
)

现在增量语句应该可以工作了.

Now the increment statement should work.

UPDATE keyspace.reviews_counts 
SET upcount = upcount + 1
WHERE review_id = '123456'

这是有关Cassandra计数器列的更多文档. http://www.datastax.com/documentation/cql/3.0/cql/cql_using/use_counter_t.html

Here is some more documentation about Cassandra counter columns. http://www.datastax.com/documentation/cql/3.0/cql/cql_using/use_counter_t.html

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