I have a simple zset named pets:
redis-cli zadd pets 1 cat1
redis-cli zadd pets 1 cat2
redis-cli zadd pets 1 cat3
redis-cli zadd pets 1 rat1
redis-cli zadd pets 1 rat2
The value is always 1. Now the set state is redis-cli zrange pets 0 -1 withscores:
1) "cat1"
2) "1"
3) "cat2"
4) "1"
5) "cat3"
6) "1"
7) "rat2"
8) "1"
9) "rat1"
10) "1"
Is there a way to merge set members based on a pattern? I want to sum all the members with the name starting with a prefix, in my case the pet type, so as to end up with the following:
1) "cat"
2) "3"
3) "rat"
4) "2"
I have tried zinterstore and zunionstore but they enforce having the same name for members of the sets.
Nope, there isn't a built-in Redis gimmick for that, but you could majik it with a Lua script (see the EVAL command).
That said, if what you need is count of pet by prefix, you should consider an alternative data model that can serve that.
Related
I'm trying to strategies how to calculate position/rank based on score and date
I have a two pieces of data with the same score shown in the image below.
If i run the command
$ZADD usersScores 11 userId6
It will add it above userId5 which is not something I want
Is it possible to add it below userId1 maybe based on date?
This is my goal essentially where i would like to show the position based on the amount and the oldest would be ontop via date
Thanks!
Sorted Set ordering
Sorted sets are ordered by their scores first, and then lexigraphically by their members if the scores are equivalent. So in your case if you added the following keys:
127.0.0.1:6379> ZADD myset 11 user1
(integer) 1
127.0.0.1:6379> ZADD myset 11 user5
(integer) 1
127.0.0.1:6379> ZADD myset 24 user3
(integer) 1
127.0.0.1:6379> zadd myset 54 user2
(integer) 1
127.0.0.1:6379> zadd myset 11 user6
(integer) 1
and then did a ZRANGE, you'd get them in ascending order with the members ordered in alphabetical order:
127.0.0.1:6379> zrange myset 0 -1 WITHSCORES
1) "user1"
2) "11"
3) "user5"
4) "11"
5) "user6"
6) "11"
7) "user3"
8) "24"
9) "user2"
10) "54"
What it looks like, is your GUI is using, or are just passing in the rev argument to ZRANGE under the hood, which orders everything in reverse (scores descending, reverse alphabetical)
127.0.0.1:6379> ZRANGE myset 0 -1 WITHSCORES REV
1) "user2"
2) "54"
3) "user3"
4) "24"
5) "user6"
6) "11"
7) "user5"
8) "11"
9) "user1"
10) "11"
Second sort-by
There are a couple of ways you could handle the second sort by with a sorted set, let's assume you wanted to do this with a 32 bit unix timestamp
You could prepend the second sortby field to the member name so if user6's score came in at 1659579650, you'd just make the member name be 1659579650:user1, then when it orders it, it would do so lexigraphically
You could combine the score with the second, since 11 is the score, we could shift 11 32 bits to the left and add/or the timestamp to it, which comes out to 48,904,219,906, those will then order correctly, and then when you want to find the score, all you need to do is right-shift the score by 32 bits.
I need to store the lowest score for each key I add to the set, but when I do ZADD, Redis overwrites the score with the new value even if the score is higher.
ZADD myorderset 1 'one' 2 'two' 3 'three'
(integer) 3
ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "two"
4) "2"
5) "three"
6) "3"
ZADD myorderset 5 'three'
(integer) 0
ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "two"
4) "2"
5) "three"
6) "5"
In the example case, I need the key 'three' not be updated since the new score is higher (5) than the existing (3). Is there a way to do this natively or do I need to create a script in Lua?
I've been researching ZADD modifiers (XX, NX, CH) but none of them do what I need.
Thank you very much!
A Lua script for this CAS use case would be the simplest and idiomatic solution:
127.0.0.1:6379> ZADD myorderset 1 'one' 2 'two' 3 'three'
(integer) 3
127.0.0.1:6379> EVAL "local s = redis.call('ZSCORE', KEYS[1], ARGV[2]) if not s or s > ARGV[1] then redis.call('ZADD', KEYS[1], ARGV[1], ARGV[2]) end" 1 myorderset 5 'three'
(nil)
127.0.0.1:6379> ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "two"
4) "2"
5) "three"
6) "3"
127.0.0.1:6379> EVAL "local s = redis.call('ZSCORE', KEYS[1], ARGV[2]) if not s or s > ARGV[1] then redis.call('ZADD', KEYS[1], ARGV[1], ARGV[2]) end" 1 myorderset 2 'three'
(nil)
127.0.0.1:6379> ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "three"
4) "2"
5) "two"
6) "2"
There is no single command or command option to do it both. You can either use combination of ZSCORE with ZADD(in lua). Alternatively("It is/looks like over-engineered") you may use ZUNIONSTORE with the aggregate option MIN.
With the AGGREGATE option, it is possible to specify how the results of the union are aggregated. This option defaults to SUM, where the score of an element is summed across the inputs where it exists. When this option is set to either MIN or MAX, the resulting set will contain the minimum or maximum score of an element across the inputs where it exists.
127.0.0.1:6379> ZADD base 1 a 2 b 5 c
(integer) 3
127.0.0.1:6379> ZADD new 3 c
(integer) 1
127.0.0.1:6379> ZUNIONSTORE base 2 base new AGGREGATE MIN
(integer) 3
127.0.0.1:6379> DEL new
(integer) 1
127.0.0.1:6379> ZRANGE base 0 -1 WITHSCORES
1) "a"
2) "1"
3) "b"
4) "2"
5) "c"
6) "3"
127.0.0.1:6379> ZADD new 5 b
(integer) 1
127.0.0.1:6379> ZUNIONSTORE base 2 base new AGGREGATE MIN
(integer) 3
127.0.0.1:6379> DEL new
(integer) 1
127.0.0.1:6379> ZRANGE base 0 -1 WITHSCORES
1) "a"
2) "1"
3) "b"
4) "2"
5) "c"
6) "3"
127.0.0.1:6379>
If you prefer,
You may generate new set name with random string in application level
Put EXPIRE to this new set, no need to DEL the new key manually after the ZUNIONSTORE, it will be expired eventually.
It can be done in MULTI/EXEC in a single transaction.
I have a redis hash store that looks like Item:<id>, with attribute name. I want to filter the hash store by a prefix for name attribute.
What I'm trying to do is store the name (lowercased) in a separate Z-set called Item:::name while setting the score to 0. By doing this, I'm successfully able to get the desired result using ZRANGEBYLEX however I'm unable to map the results back to the original Items. How should I go about implementing something like this?
I've seen multiple autocomplete examples for Redis which require the same functionality but without linking the words back to an actual Item (hash in this case)
In sorted sets the member can't be duplicated, it has to be unique. So different users with the same name will cause problem.
My suggestion requires application layer coding to parse response array and executing hash commands (it will be like secondary indexes);
127.0.0.1:6379> HSET user:1 name jack
(integer) 1
127.0.0.1:6379> HSET user:2 name john
(integer) 1
127.0.0.1:6379> HSET user:3 name keanu
(integer) 1
127.0.0.1:6379> HSET user:4 name jack
(integer) 1
127.0.0.1:6379> ZADD item:names 0 jack::user:1 0 john::user:2 0 keanu::user:3 0 jack::user:4
(integer) 4
127.0.0.1:6379> ZRANGE item:names 0 -1 WITHSCORES
1) "jack::user:1"
2) "0"
3) "jack::user:4"
4) "0"
5) "john::user:2"
6) "0"
7) "keanu::user:3"
8) "0"
127.0.0.1:6379> ZRANGEBYLEX item:names [jack [jo
1) "jack::user:1"
2) "jack::user:4"
At the end you will have name::hash-key formatted array elements. At application layer if you separate each element to two substrings by using ::(any other string such as !!! or || etc) you will have user:1 and user:4.
127.0.0.1:6379> HGETALL user:1
1) "name"
2) "jack"
127.0.0.1:6379> HGETALL user:4
1) "name"
2) "jack"
127.0.0.1:6379>
I'm tracking members in multiple Sorted Sets in Redis as a way to do multi-column indexing on the members. As an example, let's say I have two Sorted Sets, lastseen (which is epoch time) and points, and I store usernames as members in these Sorted Sets.
I'm wanting to use ZREVRANGEBYSCORE against lastseen to get a list of users who were recently seen, but I only want a user to be included in the results if its also present in the points Sorted Set.
I looked at using ZINTERSTORE to help me do this, but the available AGGREGATE options are not conducive to my scenario. If one of the AGGREGATE options was to use the score from a specific set provided to the ZINTERSTORE command, then it would work, but that's not an option.
---EDIT---
Example:
redis> ZADD lastseen 12345 "foo"
redis> ZADD lastseen 12346 "bar"
redis> ZADD lastseen 12347 "sucka"
redis> ZADD points 5 "foo"
redis> ZADD points 9 "bar"
Now, if I run:
redis> ZREVRANGEBYSCORE lastseen +inf -inf
1) "sucka"
2) "bar"
3) "foo"
What I'm looking for is a way to only get "foo" and "bar" returned by the call to ZREVRANGEBYSCORE for lastseen since "sucka" isn't resent in the points Sorted Set.
I can do:
redis> ZINTERSTORE out 2 lastseen points
redis> ZRANGE out 0 -1 WITHSCORES
1) "foo"
2) "12350"
3) "bar"
4) "12355"
As you can see, the ZINTERSTORE does cut out the "sucka" member, but the scores for the other two members get aggregated using SUM. There's two other aggregation options (MIN and MAX) available for use with ZINTERSTORE. In this case, using MAX would give me what I'm looking for, but that wouldn't be the case if a user's points were greater than the epoch value for the last time they were seen.
You can get what you're asking by setting the WEIGHT of points to 0 and of lastseen to 1 when running ZINTERSTORE so that only the weight of lastseen is considered:
redis> ZINTERSTORE out 2 lastseen points WEIGHTS 1 0
(integer) 2
Then, depending on what ordering you're going for, you can either:
redis> ZRANGE out 0 -1 WITHSCORES
1) "foo"
2) "12345"
3) "bar"
4) "12346"
or:
redis> ZREVRANGE out 0 -1 WITHSCORES
1) "bar"
2) "12346"
3) "foo"
4) "12345"
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,