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Sorted Sets

  • A mix between a Set and a Hash
  • Like sets, sorted sets are composed of unique, non-repeating string elements
  • Every element in a sorted set is associated with a floating point value called the score 
  • Similar to a hash, since every element is mapped to a value

Sorted Ordering

  • Elements in a sorted sets are taken in order. They are ordered according to the following rule

    • If A and B are two elements with a different score, then A > B if A.score is > B.score
    • If A and B have exactly the same score, then A > B if the A string is lexicographically greater than the B string. A and B
      strings can't be equal since sorted sets only have unique elements

  • Use  ZADD in order to add values to a sorted set

  • Sorted sets support all set operations

                     <key>   <score>  <value>
127.0.0.1:6379> zadd hackers   200    "viraj"

(integer) 0
127.0.0.1:6379> zadd hackers 150 "deepu"
(integer) 1
127.0.0.1:6379>

Sorted Set Operations

127.0.0.1:6379> zadd hackers 200 viraj
(integer) 1
127.0.0.1:6379> zadd hackers 200 "viraj"
(integer) 0
127.0.0.1:6379> zadd hackers 150 "deepu"
(integer) 1
127.0.0.1:6379> zrange hackers 0 -1
1) "deepu"
2) "viraj"
127.0.0.1:6379> zadd hackers 100 "karthik"
(integer) 1
127.0.0.1:6379> zadd hackers 50 "rahul"
(integer) 1
127.0.0.1:6379> zadd hackers 25 "tom"
(integer) 1
127.0.0.1:6379> zrange hackers 0 -1
1) "tom"
2) "rahul"
3) "karthik"
4) "deepu"
5) "viraj"
127.0.0.1:6379>

Operate on Ranges

  • ZRANGEBYSCORE

Example

Return all the elements with a score between negative infinity and 100

127.0.0.1:6379> zrangebyscore hackers -inf 100 
1) "tom"
2) "rahul"
3) "karthik"

Remove Elements in Range

  • ZREMRANGEBYSCORE Remove elements in range by score and returns the number of removed elements
127.0.0.1:6379> zremrangebyscore hackers 100 200
(integer) 3
127.0.0.1:6379>

For more information on sorted sets http://redis.io/topics/data-types-intro#sorted-sets