迭代通过Cassandra宽行与CQL3

本文介绍了迭代通过Cassandra宽行与CQL3的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

如何使用CQL3引入一系列复合列？

How can I pull in a range of Composite columns with CQL3?

请考虑以下内容：

CREATE TABLE Stuff (
    a int,
    b text,
    c text,
    d text,
    PRIMARY KEY (a,b,c)
);

在Cassandra中，这有效地创建了一个带有整数行（值为a）和CompositeColumns由b和c的值和字符串'd'组成。当然，这一切都是由CQL3覆盖的，所以我们会认为我们正在插入到单个数据库行...但我离题。

In Cassandra what this effectively does is creates a ColumnFamily with integer rows (values of a) and with CompositeColumns composed of the values of b and c and the literal string 'd'. Of course this is all covered up by CQL3 so that we will think that we're inserting into individual database rows... but I digress.

并考虑以下输入集合：

INSERT INTO Stuff (a,b,c,d) VALUES (1,'A','P','whatever0');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'A','Q','whatever1');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'A','R','whatever2');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'A','S','whatever3');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'A','T','whatever4');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'B','P','whatever5');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'B','Q','whatever6');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'B','R','whatever7');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'B','S','whatever8');
INSERT INTO Stuff (a,b,c,d) VALUES (1,'B','T','whatever9');

在我目前的用例中，我想读取Stuff的所有值， n 值。我如何做到这一点？这是我目前使用 n = 4 ：

In my current use case, I want to read all of the values of Stuff, n values at a time. How do I do this? Here's my current take using n=4:

SELECT * FROM Stuff WHERE a=1 LIMIT 4;

和预期一样，我得到：

 a | b | c | d
---+---+---+-----------
 1 | A | P | whatever0
 1 | A | Q | whatever1
 1 | A | R | whatever2
 1 | A | S | whatever3

我遇到的麻烦是我如何获得下4个？这是我的尝试：

The trouble that I run into is how do I get the next 4? Here is my attempt:

SELECT * FROM Stuff WHERE a=1 AND b='A' AND c>'S' LIMIT 4;

这不行，因为我们约束b等于'A'要做的事！但是我在CQL3语法中找不到任何东西，允许我继续迭代。我希望我可以做类似的事情：

This doesn't work because we've constrained b to equal 'A' - which is a reasonable thing to do! But I've found nothing in the CQL3 syntax that allows me to keep iterating anyway. I wish I could do something like:

SELECT * FROM Stuff WHERE a=1 AND {b,c} > {'A','S'} LIMIT 4;

如何达到我想要的结果。也就是说，我如何使CQL3返回：

How do I achieve my desired result. Namely, how do I make CQL3 return:

 a | b | c | d
---+---+---+-----------
 1 | A | T | whatever0
 1 | B | P | whatever1
 1 | B | Q | whatever2
 1 | B | R | whatever3

CQL3

迭代通过Cassandra宽行与CQL3

问题描述

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