Cassandra UPDATE主键值 [英] Cassandra UPDATE primary key value

问题描述

我知道这是不可能使用UPDATE。

I understand that this is not possible using an UPDATE.

我想要做的是将所有行说PK = 0到新行PK = 1。

What I would like to do instead, is migrate all rows with say PK=0 to new rows where PK=1. Are there any simple ways of achieving this?

推荐答案

对于一个相对简单的方法，你总是可以做一个快速 COPY 在cqlsh中的TO / FROM。

For a relatively simple way, you could always do a quick COPY TO/FROM in cqlsh.

假设我有一个名为emp / p>

Let's say that I have a column family (table) called "emp" for employees.

CREATE TABLE stackoverflow.emp (
    id int PRIMARY KEY,
    fname text,
    lname text,
    role text
)

我有一行。

aploetz@cqlsh:stackoverflow> SELECT * FROM emp;

 id | fname | lname | role
----+-------+-------+-------------
  1 | Angel |   Pay | IT Engineer

如果我想使用新的ID重新创建Angel，我可以 COPY 表格的内容 TO a .csv文件：

If I want to re-create Angel with a new id, I can COPY the table's contents TO a .csv file:

aploetz@cqlsh:stackoverflow> COPY stackoverflow.emp TO '/home/aploetz/emp.csv';

1 rows exported in 0.036 seconds.

现在，我将使用我最喜欢的编辑器将emp更改为emp.csv中的2 。请注意，如果您的文件中有多行（不需要更新），则可以删除它们：

Now, I'll use my favorite editor to change the id of Angel to 2 in emp.csv. Note, that if you have multiple rows in your file (that don't need to be updated) this is your opportunity to remove them:

2,Angel,Pay,IT Engineer

我将保存文件， code> COPY 更新的行返回Cassandra FROM 文件：

I'll save the file, and then COPY the updated row back into Cassandra FROM the file:

aploetz@cqlsh:stackoverflow> COPY stackoverflow.emp FROM '/home/aploetz/emp.csv';

1 rows imported in 0.038 seconds.

现在Angel在emp表中有两行。

Now Angel has two rows in the "emp" table.

aploetz@cqlsh:stackoverflow> SELECT * FROM emp;

 id | fname | lname | role
----+-------+-------+-------------
  1 | Angel |   Pay | IT Engineer
  2 | Angel |   Pay | IT Engineer

(2 rows)

有关详细信息， a href =http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/copy_r.html> DataStax doc COPY 。

For more information, check the DataStax doc on COPY.

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