How to intersect sorted sets with specific score? - redis

Question

tl:dr;
Can I do the intersection between two sorted sets, but only for the fields that have a specified score?
For example:
ZADD zset1 1 "first"
ZADD zset1 2 "second"
ZADD zset2 1 "first"
ZADD zset2 2 "second"
<command_that_I_need> <score> 2 zset1 zset2
And with score 1, would return:
1 "first"
Why do I want to do this?
Why? I'll need to explain some things first.
In my model, there are users, which can create articles.
Each article is associated to an article_id.
I want to give anyone the ability to search for article titles, and optionally specifying the user.
And I thought of this by splitting the query in words, and finding which articles contain those words.
And I'm able to do that because I store that information this way:
zadd search_words:<word> <user_id> <article_id>
Each time an article is created, its title is split in words. For each word in words, I create that sorted set.
That way, I would split each query in words, and intersect the search_words:<word> sorted sets. And I do want to filter by score because that would allow me to filter by user_id.
Note: Since the articles also have content, I'm aware that the user would want the search to look in the content, but that is out of the scope of my project, and thus I ignore that temporarily.
Note 2: Is there a better solution to this?

Answer 1

There is no single command to do your bidding in this case. One way to go about it would be to first do the ZINTERSTORE on all your sets and then do a ZRANGEBYSCORE on the result to filter by your user_id.
Note 2: your use of sorted sets' score is acceptable since apparently user_id is numeric. However, a simpler way would be to use regular sets. You can continue using the same mechanism for the words and articles but instead of storing the article_id<->user_id relationship in a score, use a dedicated set for each user, for example:
SADD articles:<user_id> <article_id>
Then, to do your query for articles for specific words and a user, just do SINTER[STORE] like so:
SINTER articles:<user_id> search_words:<word1> search_words:<word2>...