如何检查Cassandra表是否存在 [英] How to check if a Cassandra table exists

问题描述

有没有一种简单的方法来检查是否在Cassandra中使用CQL（或API，也许使用com.datastax.driver）定义表（列族）？

Is there an easy way to check if table (column family) is defined in Cassandra using CQL (or API perhaps, using com.datastax.driver)?

现在我倾向于执行 SELECT 1 FROM table 并检查异常，但也许有更好的方法？

Right now I am leaning towards executing SELECT 1 FROM table and checking for exception but maybe there is a better way?

推荐答案

从1.1开始，您应该可以查询系统键空间， schema_columnfamilies 列族。如果您知道要检查哪个键空间，此CQL应列出键空间中的所有列族：

As of 1.1 you should be able to query the system keyspace, schema_columnfamilies column family. If you know which keyspace you want to check, this CQL should list all column families in a keyspace:

SELECT columnfamily_name
FROM schema_columnfamilies WHERE keyspace_name='myKeyspaceName';

描述此功能的报告如下： https://issues.apache.org/jira/browse/CASSANDRA-2477

The report describing this functionality is here: https://issues.apache.org/jira/browse/CASSANDRA-2477

虽然，他们确实注意到一些系统列名称已在1.1和1.2之间更改。

Although, they do note that some of the system column names have changed between 1.1 and 1.2. So you might have to mess around with it a little to get your desired results.

编辑20160523 - Cassandra 3.x更新：

请注意，对于Cassandra 3.0及以上版本，您需要对上述查询进行一些调整：

Note that for Cassandra 3.0 and up, you'll need to make a few adjustments to the above query:

SELECT table_name 
FROM system_schema.tables WHERE keyspace_name='myKeyspaceName';

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