Redis learning notes - data type: ordered set (Zset)

Ordered sets are relative to hashes 、 list 、 It will be a little strange for the collection , But since it's called ordered set , So it must have something to do with the set , It preserves the property that a set cannot have duplicate members , But the difference is , Elements in an ordered set can be ordered . But it's different from a list that uses index subscripts as sort criteria , It sets a score for each element （score） Sort by .

Operations within a set

1. Add members

zadd key [nx|xx] [ch] [incr] score member [score member ...]

• nx：member Must not exist , Can be set successfully , Used to add
• xx：member There must be , Can be set successfully , Used to update the
• ch： Return after this operation , The number of elements and fractions of an ordered set that have changed
• incr： Yes score Do increase , Equivalent to the following zincrby
• Ordered sets provide sort fields compared to sets , But there are costs ,zadd The time complexity of is O（log（n））,sadd The time complexity of is O（1）.

add to key by “user:ranking” Set

127.0.0.1:6379> zadd user:ranking 150 Tom
(integer) 1
127.0.0.1:6379> zadd user:ranking 1 Charlie 14 Day 66 Ling 124 Zhang
(integer) 4

2. Count the number of members

zcard key

Calculation key by “user:ranking” Number of set members of

127.0.0.1:6379> zcard user:ranking
(integer) 5

3. Calculate the score of a member

zscore key member

Calculation key by “user:ranking” Collection members of “Charlie” The scores of

127.0.0.1:6379> zscore user:ranking Charlie
"1"

4. Calculate the ranking of members

From low to high

zrank key member

From high to low

zrevrank key member

Calculation key by “user:ranking” The ranking of the collection members of

127.0.0.1:6379> zrank user:ranking Day
(integer) 1
127.0.0.1:6379> zrank user:ranking Charlie
(integer) 0
127.0.0.1:6379> zrank user:ranking Zhang
(integer) 3

5. Delete members

zrem key member [member ...]

Delete key by “user:ranking” Collection members of “Zhang”

127.0.0.1:6379> zrem user:ranking Zhang
(integer) 1

6. Increase the score of members

zincrby key increment member

increase key by “user:ranking” Collection members of “Ling”5 branch

127.0.0.1:6379> zincrby user:ranking 5 Ling
"71"

7. Returns the member of the specified ranking range

From low to high

zrange key start end [withscores]

From high to low

zrevrange key start end [withscores]

return key by “user:ranking” The set of specifies the range and score

127.0.0.1:6379> zrange user:ranking 0 -1
1) "Charlie"
2) "Day"
3) "Ling"
4) "Tom"
127.0.0.1:6379> zrange user:ranking 0 -1 withscores
1) "Charlie"
2) "1"
3) "Day"
4) "14"
5) "Ling"
6) "71"
7) "Tom"
8) "150"

8. Returns the member of the specified score range

From low to high

zrangebyscore key min max [withscores] [limit offset count]

From high to low

zrevrangebyscore key max min [withscores] [limit offset count]

return key by “user:ranking” The set of specifies the members of the score range

127.0.0.1:6379> zrangebyscore user:ranking 10 80 withscores
1) "Day"
2) "14"
3) "Ling"
4) "71"
127.0.0.1:6379> zrevrangebyscore user:ranking 80 10 withscores
1) "Ling"
2) "71"
3) "Day"
4) "14"

min and max Default closed interval , Support open range （ parentheses ）,-inf and +inf They represent infinitesimally small and infinitesimally large

127.0.0.1:6379> zrangebyscore user:ranking 10 +inf withscores
1) "Day"
2) "14"
3) "Ling"
4) "71"
5) "Tom"
6) "150"
127.0.0.1:6379> zrevrangebyscore user:ranking 80 -inf withscores
1) "Ling"
2) "71"
3) "Day"
4) "14"
5) "Charlie"
6) "1"
127.0.0.1:6379> zrevrangebyscore user:ranking 71 -inf withscores
1) "Ling"
2) "71"
3) "Day"
4) "14"
5) "Charlie"
6) "1"
127.0.0.1:6379> zrevrangebyscore user:ranking (71 -inf withscores
1) "Day"
2) "14"
3) "Charlie"
4) "1"

9. Returns the number of members in the specified score range

zcount key min max

return key by “user:ranking” Specifies the number of members of the score range

127.0.0.1:6379> zcount user:ranking 10 80
(integer) 2

10. Deletes the ascending element in the specified ranking

zremrangebyrank key start stop

11. Deletes the member of the specified score range

zremrangebyscore key min max

Operations between sets

Add test data

127.0.0.1:6379> zadd user:ranking:1 1 Carlie 15 Day 67 Lin 124 Zhang
(integer) 4
127.0.0.1:6379> zadd user:ranking:2 5 Tom 35 Jerry 564 Zhang
(integer) 3

1. intersection

zinterstore destination numkeys key [key ...] [weights weight [weight ...]] [aggregate sum|min|max]

• destination： The intersection calculation is saved to this key
• numkeys： You have to do the intersection to calculate the number of keys
• key[key…]： The key that needs to do the intersection computation
• weights weight[weight…]： The weight of each key , When you do the intersection calculation , Each of these keys member I'm going to multiply my score by this weight , The weight of each key is by default 1
• aggregate sum|min|max： After the member intersection is calculated , The score can be calculated by sum（ and ）、min（ minimum value ）、max（ Maximum ） Make a summary , The default value is sum

The following operation is right user：ranking：1 and user：ranking：2 Do intersection ,weights and aggregate Default configuration used , You can see the target key user：ranking：1_inter_2 The score was sum operation

127.0.0.1:6379> zinterstore user:ranking:1_inter_2 2 user:ranking:1 user:ranking:2
(integer) 1
127.0.0.1:6379> zrange user:ranking:1_inter_2 0 -1 withscores
1) "Zhang"
2) "688"

2. Combine

zunionstore destination numkeys key [key ...] [weights weight [weight ...]] [aggregate sum|min|max]

Generate key by “user:ranking:1_union_2” Union

127.0.0.1:6379> zunionstore user:ranking:1_union_2 2 user:ranking:1 user:ranking:2
(integer) 6
127.0.0.1:6379> zrange user:ranking:1_union_2 0 -1 withscores
1) "Carlie"
2) "1"
3) "Tom"
4) "5"
5) "Day"
6) "15"
7) "Jerry"
8) "35"
9) "Lin"
10) "67"
11) "Zhang"
12) "688"

Internal encoding

• ziplist（ Compressed list ）： When the number of elements in an ordered set is less than zset-max-ziplist-entries To configure （ Default 128 individual ）, At the same time, the value of each element is less than zset-max-ziplist-value To configure （ Default 64 byte ） when ,Redis Will use ziplist As an internal implementation of an ordered set ,ziplist Can effectively reduce the use of memory
• skiplist（ Skip list ）： When ziplist When the conditions are not met , Ordered sets will use skiplist As an internal implementation , Because at this time ziplist The efficiency of reading and writing will decrease .

Use scenarios

Ranking system

1. To add user likes, you can use zadd and zincrby function
2. Cancel user likes , Users cheat or log out , It can be used zrem
3. Show leaderboard use zrevrange command
4. To display user information or scores, you can use zscore and zrank Two functions