Cassandra批处理语句 - 执行顺序 [英] Cassandra batch statement - Execution order

问题描述

我有一个Cassandra的批处理语句，其中包含一个具有相同分区键的delete和insert语句，其中delete是第一个语句，insert是第二个语句。批处理语句如何执行这些语句？是否按照相同的顺序，我们添加了语句？

I have a batch statement of Cassandra that contains a delete and an insert statement of same partition key, where delete is the first statement and insert is the second. How the batch statement executes these statements ? Is in the same order in which,we added the statements?

推荐答案

不，它不会按照指定的顺序执行。要强制执行特定的执行顺序，可以添加 USING TIMESTAMP 子句。有关详细信息，请查看文档： http：//docs.datastax。 com / en / cql / 3.1 / cql / cql_reference / batch_r.html

No, it does not execute them in the order specified. To force a particular execution order, you can add the USING TIMESTAMP clause. Check the docs for more information: http://docs.datastax.com/en/cql/3.1/cql/cql_reference/batch_r.html

使用时间戳记如何维持订单的执行。例如如果上面的例子（删除和插入同一分区键），最终结果应该是插入的记录。是否可以添加时间戳？

Using time stamp how it can maintain the order of execution . For Example if the above example (delete and insert for same partition key), the final result should be the inserted record. Is that possible by adding time-stamp ??

是的。我将结合上面的链接和 DELETE文档 a>来演示，开始创建一个名为购买的简单表格，其中包含两个字段：

Yes. I'll combine examples from the link above and the DELETE documentation to demonstrate, and start by creating a simple table called purchases with two fields:

CREATE TABLE purchases (user text PRIMARY KEY, balance bigint);

接下来，我将使用INSERT和DELETE执行批处理。我将使用DELETE最后一个，但具有比INSERT更早的时间戳：

Next, I'll execute a batch with an INSERT and a DELETE. I'll do the DELETE last, but with an earlier timestamp than the INSERT:

BEGIN BATCH
  INSERT INTO purchases (user, balance) VALUES ('user1', -8) USING TIMESTAMP 1432043350384;
  DELETE FROM purchases USING TIMESTAMP 1432043345243 WHERE user='user1';
APPLY BATCH;

当我查询 userid ：

When I query for userid:

aploetz@cqlsh:stackoverflow2> SELECT user, balance, writetime(balance) FROM purchases WHERE user='user1';

 user  | balance | writetime(balance)
-------+---------+--------------------
 user1 |      -8 |      1432043350384

(1 rows)

如您所见，因为它有最新的时间戳。而如果我只是从cqlsh提示符运行INSERT和DELETE（按顺序），则查询将不返回任何内容。

As you can see, the INSERT persisted because it had the latest timestamp. Whereas if I had simply run the INSERT and DELETE (in that order) from the cqlsh prompt, the query would have returned nothing.

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