从 Spring Boot 向 Cassandra 动态添加列

Question

我正在尝试从 Spring Boot 应用程序动态添加新列。让我们说，每次事件 e 发生时，我都想在 Cassandra 表中添加一个具有明确定义的列名和类型的列。我试过这段代码：

    @Query("alter table attributes.attributedata add ?0 ?1")
    public void addColumn(String columnName, String dataType);

错误日志：

    org.springframework.cassandra.support.exception.CassandraQuerySyntaxException: line 1:41 no viable alternative at input 'gac5' (alter table attributes.attributedata add ['gac]...); nested exception is com.datastax.driver.core.exceptions.SyntaxError: line 1:41 no viable alternative at input 'gac5' (alter table attributes.attributedata add ['gac]...)
    at org.springframework.cassandra.support.CassandraExceptionTranslator.translateExceptionIfPossible(CassandraExceptionTranslator.java:132)
    at org.springframework.cassandra.core.CqlTemplate.potentiallyConvertRuntimeException(CqlTemplate.java:946)
    at org.springframework.cassandra.core.CqlTemplate.translateExceptionIfPossible(CqlTemplate.java:930)
    at org.springframework.cassandra.core.CqlTemplate.translateExceptionIfPossible(CqlTemplate.java:912)
    at org.springframework.cassandra.core.CqlTemplate.doExecute(CqlTemplate.java:278)
    at org.springframework.cassandra.core.CqlTemplate.doExecute(CqlTemplate.java:559)
    at org.springframework.cassandra.core.CqlTemplate.doExecute(CqlTemplate.java:549)
    at org.springframework.cassandra.core.CqlTemplate.query(CqlTemplate.java:485)
    at org.springframework.cassandra.core.CqlTemplate.query(CqlTemplate.java:510)
    at org.springframework.cassandra.core.CqlTemplate.query(CqlTemplate.java:505)
    at org.springframework.data.cassandra.core.CassandraTemplate.selectOne(CassandraTemplate.java:638)
    at org.springframework.data.cassandra.core.CassandraTemplate.selectOne(CassandraTemplate.java:509)
    at org.springframework.data.cassandra.repository.query.CassandraQueryExecution$SingleEntityExecution.execute(CassandraQueryExecution.java:104)
    at org.springframework.data.cassandra.repository.query.CassandraQueryExecution$ResultProcessingExecution.execute(CassandraQueryExecution.java:143)
    at org.springframework.data.cassandra.repository.query.AbstractCassandraQuery.execute(AbstractCassandraQuery.java:113)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:483)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:461)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:56)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:57)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)

我还尝试将整个查询存储到一个字符串中，然后直接将字符串放入值中，这样 @Query(value="?0") 但这也不起作用。

这段代码运行良好。如果从函数获得的值没有包含在单引号内，则代码将起作用。

    @Query("alter table attributes.attributedata add dummy text")
    public void addColumn(String columnName, String dataType);

有什么办法可以做到吗？请提出可能的替代方案。

Answer 1

可以创建一个集群对象，如代码所示，然后是执行查询的会话对象。要添加的列的名称和类型作为参数传递。

   public void addColumn(String columnName, String columnType){

      //Query
      String query = "ALTER TABLE keyspace.tablename ADD " + columnName + " " + columnType;

      //Creating Cluster object
      Cluster cluster = Cluster.builder().addContactPoint("127.0.0.1").build();
   
      //Creating Session object
      Session session = cluster.connect();
 
      //Executing the query
      session.execute(query);
 
      System.out.println("Column added");
   }

为了优化代码，我们可以在应用启动时只创建一次会话对象。这种场景的实现如下：

   private Session session;

   @EventListener(ApplicationReadyEvent.class)
   private void createSessionObject(){
      //Creating Cluster object
      Cluster cluster = Cluster.builder().addContactPoint("127.0.0.1").build();
   
      //Creating Session object
      Session session = cluster.connect();
   }

   public void addColumn(String columnName, String columnType){

      //Query
      String query = "ALTER TABLE keyspace.tablename ADD " + columnName + " " + columnType;

      if(session == null){
         createSessionObject();
      }
 
      //Executing the query
      session.execute(query);
 
      System.out.println("Column added");
   }

Answer 2

您可以使用 CONCAT 尝试类似的操作

@Query("alter table attributes.attributedata add CONCAT('%',:columnNameDataType,'%')")
public void addColumn(String columnNameDataType);

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