Redis learning notes - data type: Set

aggregate （set） Types are also used to hold multiple string elements , But unlike the list type , Duplicate elements are not allowed in the collection , And the elements in the set are unordered , Elements cannot be retrieved by index index .

Operations within a set

1. Additive elements

<pre>sadd key element [element ...]</pre>

add to key by “myset” Set , Returns the number of additions

127.0.0.1:6379> sadd myset a b c
(integer) 3
127.0.0.1:6379> sadd myset a b
(integer) 0

2. Get all the elements

smembers key

obtain key by “myset” All elements of the collection

127.0.0.1:6379> smembers myset
1) "c"
2) "a"
3) "b"

3. Remove elements

srem key element [element ...]

Delete key by “myset” A collection of “a” Elements

127.0.0.1:6379> srem myset a
(integer) 1

4. Count the number of elements

scard key

Calculation key by “myset” The number of elements in the set

127.0.0.1:6379> scard myset
(integer) 2

5. Determines whether an element is in the set

sismember key element

Judge key by “myset” The elements of the collection

127.0.0.1:6379> sismember myset b
(integer) 1
127.0.0.1:6379> sismember myset a
(integer) 0

6. Returns the specified number of elements at random from the collection

srandmember key count

Random from key by “myset” Collection return element

127.0.0.1:6379> srandmember myset 1
1) "b"
127.0.0.1:6379> srandmember myset 1
1) "b"
127.0.0.1:6379> srandmember myset 1
1) "c"

7. Pop up randomly from the collection （ Delete ） Elements （ You can specify the number ）

spop key [count]

Random delete key by “myset” The elements in the collection

127.0.0.1:6379> smembers myset
1) "c"
2) "a"
3) "b"
127.0.0.1:6379> spop myset 1
1) "b"
127.0.0.1:6379> spop myset
"a"
127.0.0.1:6379> smembers myset
1) "c"

Assembly room operation

Add test data

127.0.0.1:6379> sadd act:1 My name is Tom
(integer) 4
127.0.0.1:6379> sadd act:2 It is Jerry
(integer) 3

1. Find the intersection of sets

sinter key [key...]

seek key by “act:1” and “act:2” Intersection

127.0.0.1:6379> sinter act:1 act:2
1) "is"

2. Find the union of sets

sunion key [key ...]

seek key by “act:1” and “act:2” Intersection

127.0.0.1:6379> sunion act:1 act:2
1) "name"
2) "is"
3) "Tom"
4) "Jerry"
5) "My"
6) "It"

3. Find the difference set of multiple sets

sdiff key [key ...]

seek key by “act:1” and “act:2” The difference between the set

127.0.0.1:6379> sdiff act:1 act:2
1) "Tom"
2) "My"
3) "name"

4. The intersection 、 Combine 、 Save the result of the difference set

sinterstore destination key [key ...]
sunionstore destination key [key ...]
sdiffstore destination key [key ...]

preservation key by “act:1” and “act:2” The intersection of is key name “act:1_2:inter”

127.0.0.1:6379> sinterstore act:1_2:inter act:1 act:2
(integer) 1
127.0.0.1:6379> smembers act:1_2:inter
1) "is"

Internal encoding

• intset（ Set of integers ）： When all the elements in the set are integers and the number of elements is less than set-max-intset-entries To configure （ Default 512 individual ） when ,Redis Will choose intset As an internal implementation of a collection , Thus reducing the use of memory .
• hashtable（ Hashtable ）： When the set type cannot satisfy intset The condition of ,Redis Will use hashtable As an internal implementation of a collection .

Use scenarios

• sadd=Tagging（ label ）
• spop/srandmember=Random item（ Generate random number , For example, lottery ）
• sadd+sinter=Social Graph（ Social needs ）