时间戳/日期作为 cassandra 列族/赫克托的键 [英] Timestamp / date as key for cassandra column family / hector

问题描述

我必须创建和查询复合键为 [timestamp,long] 的列族.还，查询时我想触发时间戳范围查询(例如 xxx 和 yyy 之间的时间戳)这可能吗?

I have to create and query a column family with composite key as [timestamp,long]. Also, while querying I want to fire range query for timestamp (like timestamp between xxx and yyy) Is this possible ?

目前我正在做一些非常有趣的事情(我知道这是不正确的).我为给定的范围创建带有时间戳字符串的键，并与 long 连接.

Currently I am doing something really funny (Which I know its not correct). I create keys with timestamp string for given range and concatenate with long.

like ,
1254345345435-1234
3423432423432-1234
1231231231231-9999

并将一组密钥传递给 hector api.(所以如果我有 1 个月的日期范围并且我想要每分钟的数据，我创建 30 * 24 * 60 * [二级键的数量 - 长])

and pass set of keys to hector api. (so if i have date range for 1 month and I want every minute data, i create 30 * 24 * 60 * [number of secondary key - long])

我可以用复合键解决连接问题.但查询部分是我想要理解的.

I can solve concatenation issue with composite key. But query part is what I am trying to understand.

据我所知，当我们使用 RandomPartitioner 时，我们无法真正基于范围进行查询，因为键是 MD5 校验和.这种用例的理想设计是什么?

As far as I understood, As we are using RandomPartitioner we cannot really query based on range as keys are MD5 checksum. Whats ideal design for this kind of use case ?

我的架构和要求如下:(实际csh)

my schema and requirements are as follows : (actual csh)

    CREATE TABLE report(
        ts timestamp,
        user_id long,
        svc1 long,
        svc2 long,
        svc3 long,
        PRIMARY KEY(ts, user_id));

select from report where ts between (123445345435 and 32423423424) and user_id is in (123,567,987)

推荐答案

您不能对复合键的第一个组件进行范围查询.相反，您应该编写一个标记值，例如daystamp(当天午夜的unix 纪元)作为键，然后将复合列写入timestamp:long.通过这种方式，您可以提供构成您的范围的键，并在复合列的时间戳组件上进行切片.

You cannot do range queries on the first component of a composite key. Instead, you should write a sentinel value such as a daystamp (the unix epoch at midnight on the current day) as the key, then write a composite column as timestamp:long. This way you can provide the keys that comprise your range, and slice on the timestamp component of the composite column.

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