Redis 动态排序 [英] Dynamic sort with Redis

问题描述

假设我的 Redis 数据库中有 5 个条目:

Let's say I have 5 entries in my Redis database:

• news::id:最后一条新闻的ID；
• news::list:所有新闻ID的列表；
• news:n 其中 n 是新闻 ID:一个包含 title、url 等字段的哈希值等；
• news:n:upvotes:所有为新闻点赞的用户 ID 的列表，从而给出了点赞数.
• news:n:downvotes:所有对新闻投反对票的用户 ID 的列表，从而给出投反对票的数量.

• news::id: the ID of the last news;
• news::list: a list of all news IDs;
• news:n where n is the news ID: a hash containing fields such as title, url, etc.;
• news:n:upvotes: a list of all users' IDs who upvoted the news, thus giving the number of upvotes.
• news:n:downvotes: a list of all users' IDs who downvoted the news, thus giving the number of downvotes.

然后我有多种排名算法，其中 rank =:

Then I have multiple ranking algorithms, where rank =:

1. upvotes_count;
2. upvotes_count - downvotes_count;
3. upvotes_count - downvotes_count - 年龄;
4. upvotes_count/downvotes_count;
5. 年龄.

现在我如何根据这些算法对这些新闻进行排序?

Now how do I sort those news according to each of these algorithms?

我想过计算每张选票的不同排名，但是如果我引入一种新算法，我需要计算所有新闻的新排名.

I thought about computing the different ranks on every votes, but then if I introduce a new algorithm I need to compute the new rank for all the news.

EVAL 可能会有所帮助，但要到 v2 才能使用.6，我当然不想等.

EVAL could help but it won't be available until v2.6, which surely I don't want to wait for.

最终，我可以检索所有新闻并将它们放入 Python 列表中.但它再次转化为高内存使用率，更不用说Redis将其数据存储在内存中这一事实.

Eventually, I could retrieve all the news and put them in a Python list. But again it translates into a high memory usage, not to mention the fact that Redis stores its data in memory.

那么有没有合适的方法来做到这一点，还是我应该转移到 MongoDB?

So is there a proper way to do this or should I just move to MongoDB?

推荐答案

您可以按存储在键中的常量进行排序.

You can sort by constants stored in keys.

在您的示例中，我几乎可以使用 Redis 对 1. 进行排序.如果您在计算后存储其他表达式值，您也可以按它们排序.对于 1.，您需要将列表计数存储在某处，我假设 news:n:upvotes:count.

In your example, I can sort 1. almost trivially using Redis. If you store the other expression values after calculating them, you can sort by them too. For 1., you will need to store the list count somewhere, I will assume news:n:upvotes:count.

问题在于使用 SORT 命令.例如，第一种排序是:

The catch is to use the SORT command. For instance, the first sort would be:

SORT news::list BY news:*:upvotes:count GET news:*->title GET news:*->url

...获得按赞数排序的标题和网址，按新月顺序排列.

...to get titles and urls sorted by upvotes, in crescent order.

也有修饰符，用于alpha 排序和asc/desc 排序.完整阅读命令页面，值得.

There are modifiers too, for alpha sorting, and asc/desc sorting. Read the command page entirely, it is worthwhile.

PS:您可以在 MULTI/中包装计数、存储、排序和可能的删除计数EXEC 环境(一个事务).

PS: You can wrap the count, store, sort and possibly deletion of count in a MULTI/EXEC environment (a transaction).

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