更新Cassandra中多个表中的行

1 回答

• 1

  其他人在谷歌小组上问了how to batch update multiple tables . 他们referred to a C# driver example的多表更新 . 该原则适用于Java，我已经从cassandra java driver复制了相关的 BatchStatement 方法 .

  下面引用Java驱动程序的相关代码：

  /**
       * Adds a new statement to this batch.
       * <p/>
       * Note that {@code statement} can be any {@code Statement}. It is allowed to mix
       * {@code RegularStatement} and {@code BoundStatement} in the same
       * {@code BatchStatement} in particular. Adding another {@code BatchStatement}
       * is also allowed for convenience and is equivalent to adding all the {@code Statement}
       * contained in that other {@code BatchStatement}.
       * <p/>
       * When adding a {@code BoundStatement}, all of its values must be set, otherwise an
       * {@code IllegalStateException} will be thrown when submitting the batch statement.
       * See {@link BoundStatement} for more details, in particular how to handle {@code null}
       * values.
       * <p/>
       * Please note that the options of the added Statement (all those defined directly by the
       * {@link Statement} class: consistency level, fetch size, tracing, ...) will be ignored
       * for the purpose of the execution of the Batch. Instead, the options used are the one
       * of this {@code BatchStatement} object.
       *
       * @param statement the new statement to add.
       * @return this batch statement.
       * @throws IllegalStateException if adding the new statement means that this
       *                               {@code BatchStatement} has more than 65536 statements (since this is the maximum number
       *                               of statements for a BatchStatement allowed by the underlying protocol).
       */
      public BatchStatement add(Statement statement) {
  
          // We handle BatchStatement here (rather than in getIdAndValues) as it make it slightly
          // easier to avoid endless loop if the use mistakenly pass a batch that depends on this
          // object (or this directly).
          if (statement instanceof BatchStatement) {
              for (Statement subStatements : ((BatchStatement) statement).statements) {
                  add(subStatements);
              }
          } else {
              if (statements.size() >= 0xFFFF)
                  throw new IllegalStateException("Batch statement cannot contain more than " + 0xFFFF + " statements.");
              statements.add(statement);
          }
          return this;
      }
  

  基本思想是为每个表更新创建一个变量，并将每个变量添加到 BatchStatement 函数中 .

  回复于 2024-05-06T03:31:08+08:00