How do I get most weighted elements from a sorted set, but excluding those found in another set(or list or hash).
>zadd all 1 one
>zadd all 2 two
>zadd all 3 three
>sadd disabled 2
>sdiff all disabled
(error) WRONGTYPE Operation against a key holding the wrong kind of value
Is my only option is to get elements from the sorted set one-by-one and compare to the list of "disabled" items? Wouldn't that be very slow because of so many transactions to a server?
What is the approach here?
Note: I assume you've meant sadd disabled two
As you've found out, SDIFF does not operate on sorted sets - that is because defining the difference between sorted sets isn't trivial.
What you could do is first create a temporary set with ZUNIONSTORE and set the intersect's scores to 0. Then do a range excluding the 0, e.g.:
127.0.0.1:6379> ZADD all 1 one 2 two 3 three
(integer) 3
127.0.0.1:6379> SADD disabled two
(integer) 1
127.0.0.1:6379> ZUNIONSTORE tmp 2 all disabled WEIGHTS 1 0 AGGREGATE MIN
(integer) 3
127.0.0.1:6379> ZREVRANGEBYSCORE tmp +inf 1 WITHSCORES
1) "three"
2) "3"
3) "one"
4) "1"
Related
I have a large set of ids (around 100000) which I want to store in redis.
I am looking for the most optimal way through which I can check if a given list of ids, what are the ids that are part of my set.
If I use a redis set, I can use SISMEMBER to check if a id is part of my set, but in this case I want to check if, given a list of ids, which one is part of my set.
Example:
redis> SADD myset "1"
(integer) 1
redis> SADD myset "2"
(integer) 2
redis> MYCOMMAND myset "[1,2,4,5]"
(list) 1, 2
Does anything of this sort exist already ?
thanks !
I am new to sorted sets in Redis (3.0.2). I basically want to update my value in sorted sets of Redis based on unique key. As of now "zadd" each time keeps on adding new values to a specific key.
As of now:
127.0.0.1:6379> zadd xyz 1 "abc"
(integer) 1
127.0.0.1:6379> zadd xyz 1 "newabc"
(integer) 1
127.0.0.1:6379> zrange xyz 0 -1
1) "abc"
2) "newabc"
Required Output: (It should over write the xyz key's value from "abc" to "newabc"
127.0.0.1:6379> zadd xyz 1 "abc"
(integer) 1
127.0.0.1:6379> zadd xyz 1 "newabc"
(integer) 1
127.0.0.1:6379> zrange xyz 0 -1
1) "newabc"
A sorted set in Redis is a set when we talk about the element, while multiple different elements can coexist with the same score.
If you want that output, you'll need to design a different data model, and since I don't know your actual issue or what's your goal in your project, I won't be able to provide a clear solution.
I have an ordered set in Redis (I am actually using a python client https://github.com/andymccurdy/redis-py), for example:
zadd myset 1 key1
zadd myset 1 key2
zadd myset 1 key3
zadd myset 0 key4
Note that 3 keys have the same score.
Using ZRANGE, i would like to get the top 2 entries (i.e lowest scores). "key4" will always be the first result as it has a lower value, but I would like the second return value to be randomly selected between the ties: key1,key2,key3. ZRANGE actually returns the keys in the order they are indexed: "keys1" is always my second result:
zrange myset 0 -1 WITHSCORES
1) "key4"
2) "0"
3) "key1"
4) "1"
5) "key2"
6) "1"
7) "key3"
8) "1"
any idea?
thanks,
J.
As kindly requested by Linus G Thiel, here are more details about my usecase:
I would like to use zsets to perform a simple ranking system. I have a list of items, for each one a score representing the relevance of the item. For the cold start of my system, most of the scores will be identical (i.e 0), and I would like to randomly select among the items having the same score. Otherwise I will always return the exact same lexicographic ordering, which will introduce a bias in the system.
The solution you propose, using one specific set for each duplicated score value will work. I will give it a try.
Thanks,
Let's suppose I want have redis hash a = {1:10, 2:15, 3:5, 4:0, 5:20}, and a set b = (5,3,4). I want to get a list containing elements from b, sorted by values of a[b] (result in this case is [4,3,5]).
When I try to do this, it doesn't work well.
redis 127.0.0.1:6379> hmset a 1 10 2 15 3 5 4 0 5 20
redis 127.0.0.1:6379> sadd b 5 3 4
redis 127.0.0.1:6379> sort b by a->*
1) "3"
2) "4"
3) "5"
Obviously, asterisk in hash field placeholder doesn't work. Are there other ways beside declaring a:1-a:5 to do this task by means of Redis?
P.S. This is not a duplicate of Redis : How can I sort my hash by keys?, as that question clearly discusses the a:* approach.
this is a know issue: link
you could do the following:
redis 127.0.0.1:6379> sadd b 5 3 4
redis 127.0.0.1:6379> zadd a 10 1 15 2 5 3 0 4 20 5
redis 127.0.0.1:6379> zinterstore result 2 a b
redis 127.0.0.1:6379> zrange result 0 -1
1) "4"
2) "3"
3) "5"
Maybe you can model it using sorted sets instead? Use the values as score, and the keys as members. Sorted sets are more or less like hashes sorted by value. I'd love to give you an example, but I'm not sure exactly what the problem you're trying to solve is. If you could elaborate maybe I could help.
Assume I have a set (or sorted set or list if that would be better) A of 100 to 1000 strings.
Then I have a sorted set B of many more strings, say one million.
Now C should be the intersection of A and B (of the strings of course).
I want to have every tuple (X, SCORE_OF_X_IN_B) where X is in C.
Any Idea?
I got two ideas:
Interstore
store A a sorted set with every score being 0
interstore to D
get every item of D
delete D
Simple loop in client
loop over A in my client programm
get zscore for every string
While 1. has way too much overhead on the redis side (Has to write for example. The redis page states quite a high time complexity, too http://redis.io/commands/zinterstore), 2. would have |A| database connections and won't be a good choice.
Maybe I could write a redis/lua script which will work like zscore but with an arbitrary number of strings, but I'm not sure if my hoster allows scripts...
So I just wanted to ask SO, if there is an elegant and fast solution available without scripting!
There is a simple solution to your problem: ZINTERSTORE will work with a SET and a ZSET. Try:
redis> sadd foo a
(integer) 1
redis> zadd bar 1 a
(integer) 1
redis> zadd bar 2 b
(integer) 1
redis> zinterstore baz 2 foo bar AGGREGATE MAX
(integer) 1
redis> zrange baz 0 -1 withscores
1) "a"
2) "1"
Edit: I added AGGREGATE MAX above, since redis will give each member of the (non-sorted) set foo a default score of 1, and SUM that with whatever score it has in the (sorted) set bar.