Shulou(Shulou.com)06/01 Report--

Redis currently supports five data types, namely

String (string)

List (list)

Hash (dictionary)

Set (collection)

Sorted Set (ordered set)

Redis data type

1. String type

SET key value sets key=value

The value corresponding to GET key or key key

GETRANGE key start end gets the substring of the string stored in a key

GETSET key value sets the string value of the key and returns the old value

GETBIT key offset returns the offset of the string value stored in the key value

MGET key1 [key2..] Get the values of all the given keys

SETBIT key offset value sets or clears the offset of the bit in the string value stored in the key

Set the value when the SETEX key seconds value key expires

SETNX key value sets the value of the key only if the key does not exist

SETRANGE key offset value overrides the offset of part of the string from the specified key

STRLEN key gets the length of the value stored in the key

MSET key value [key value...] Set multiple keys and values

MSETNX key value [key value...] Set multiple keys and multiple values, only when there is no key

Millisecond value and expiration time of PSETEX key milliseconds value setting key

INCR key increases the integer value of the key once

INCRBY key increment increments the integer value of keys by a given number of keys

INCRBYFLOAT key increment increases the floating-point value of keys by a given number of keys

The integer value of the DECR key decrement key once

DECRBY key decrement is the integer value of a given number of decreasing keys

APPEND key value add value to a key

Operation management command

DEL key if there is a delete key

DUMP key returns the serialized version of the value stored in the specified key

EXISTS key this command checks whether the key exists

EXPIRE key seconds specifies the expiration time of the key

The key expiration time specified by EXPIREAT key timestamp. In this case, the time is in Unix timestamp format

PEXPIRE key milliseconds setting key expires in milliseconds

The PEXPIREAT key milliseconds-timestamp setting key expires in milliseconds specified in the Unix timestamp

KEYS pattern finds all keys that match the specified pattern

MOVE key db move key to another database

PERSIST key removes expired keys

PTTL key gets the expiration key for the remaining time in milliseconds.

TTL key gets the remaining time for the key to expire.

RANDOMKEY returns a random key from Redis

The name of the RENAME key newkey change key

RENAMENX key newkey rename key, if the new key does not exist

TYPE key returns the value of the data type stored in the key.

Examples of operational use

Redis 127.0.0.1 set baidu http://www.baidu 6379

OK

Redis 127.0.0.1 6379 > append baidu .com

(integer) 20

Redis 127.0.0.1 6379 > get baidu

"http://www.baidu.com"

Redis 127.0.0.1 6379 > set visitors 0

OK

Redis 127.0.0.1 6379 > incr visitors

(integer) 1

Redis 127.0.0.1 6379 > incr visitors

(integer) 2

Redis 127.0.0.1 6379 > get visitors

"2"

Redis 127.0.0.1 6379 > incrby visitors

(integer) 102

Redis 127.0.0.1 6379 > get visitors

"102"

Redis 127.0.0.1 6379 > type baidu

String

Redis 127.0.0.1 6379 > type visitors

String

Redis 127.0.0.1 6379 > ttl baidu

(integer)-1

Redis 127.0.0.1 6379 > rename baidu baidu-site

OK

Redis 127.0.0.1 6379 > get baidu

(nil)

Redis 127.0.0.1 6379 > get baidu-site

"http://www.baidu.com"

2. List (list)

A Redis list is a simple list of strings, which can be compared to the std::list in C++. It is simply a linked list or a queue. You can add elements to the Redis list from the head or tail. The maximum length of a list is 2 ^ 32-1, which means that each list supports more than 4 billion elements.

The implementation of Redis list is a two-way linked list, that is, it can support reverse search and traversal, which is more convenient to operate, but it brings some additional memory overhead. Many implementations within Redis, including send buffer queues, also use this data structure.

Application scenario

There are many application scenarios of Redis list, and it is also one of the most important data structures of Redis. For example, the watch list and fan list of twitter can be implemented using the list structure of Redis. For example, some applications use the list type of Redis to implement a simple lightweight message queue, producer push, consumer pop/bpop.

Related command

BLPOP

BLPOP key1 [key2] timeout takes out and gets the first element in the list, or blocks until it is available

BRPOP

BRPOP key1 [key2] timeout takes out and gets the last element in the list, or blocks until it is available

BRPOPLPUSH

BRPOPLPUSH source destination timeout pops a value from the list, pushes it to another list and returns it, or blocks until it is available

LINDEX

LINDEX key index gets the corresponding element from a list with its index

LINSERT

LINSERT key BEFORE | AFTER pivot value inserts an element after or before other elements in the list

LLEN

LLEN key gets the length of the list

LPOP

LPOP key gets and fetches the first element in the list

LPUSH

LPUSH key value1 [value2] preceded by a list of one or more values

LPUSHX

LPUSHX key value adds a values list in front of it, only if it exists in the list

LRANGE

LRANGE key start stop gets various elements from a list

LREM

LREM key count value removes an element from the list

LSET

LSET key index value sets the value of an element in the index in the list

LTRIM

LTRIM key start stop trim list to the specified range

RPOP

RPOP key takes out and gets the last element in the list

RPOPLPUSH

RPOPLPUSH source destination deletes the list of the last element, appends it to another list, and returns it

RPUSH

RPUSH key value1 [value2] add one or more values to the list

RPUSHX

RPUSHX key value adds a list of values only if it exists in the list

Use the example

Redis 127.0.0.1 6379 > lpush list1 redis

(integer) 1

Redis 127.0.0.1 6379 > lpush list1 hello

(integer) 2

Redis 127.0.0.1 6379 > rpush list1 world

(integer) 3

Redis 127.0.0.1 6379 > llen list1

(integer) 3

Redis 127.0.0.1 6379 > lrange list1 0 3

1) "hello"

2) "redis"

3) "world"

Redis 127.0.0.1 6379 > lpop list1

"hello"

Redis 127.0.0.1 6379 > rpop list1

"world"

Redis 127.0.0.1 6379 > lrange list1 0 3

1) "redis"

3. Hash (dictionary, hash table)

Similar to the dict type in C# or the hash_map type in C++.

Redis Hash is actually a HashMap inside the Value. In fact, there are two different implementations. When the number of members of this Hash is small, the Redis will use a compact storage method similar to an one-dimensional array to save memory, instead of using the real HashMap structure. The encoding of the corresponding value redisObject is zipmap. When the number of members increases, it will be automatically converted to the real HashMap, and the encoding will be ht.

Application scenario

Suppose there are multiple users and corresponding user information, which can be used to store user ID as key, and serialize user information into such as json format as value to save.

Related command

HDEL

HDEL key field [field...] Delete one or more property fields of an object, and attributes that do not exist will be ignored

HEXISTS

HEXISTS key field to see if the property field exists for the object

HGET

HGET key field gets the value of the field attribute field in the object

HGETALL

HGETALL key gets all property fields and values of an object

HINCRBY

HINCRBY key field value increases the value of the specified field in the object by a given value, and the atomic self-increment operation can only be used for the attribute value of integer.

HINCRBYFLOAT

HINCRBYFLOAT key field increment increases the value of the specified field in the object by a given floating point number

HKEYS

HKEYS key gets all the property fields of an object

HVALS

HVALS key gets all attribute values of an object

HLEN

HLEN key gets the total number of all property fields of the object

HMGET

HMGET key field [field...] Gets the value of one or more specified fields of the object

HSET

HSET key field value sets the value of the specified field of the object

HMSET

HMSET key field value [field value...] Set the value of one or more fields in the object at the same time

The HSETNX:HSETNX command is used to set fields in the hash of stored key values, only if the field does not exist.

If the key does not exist, the new key is created by the hash. If the field already exists, the operation has no effect.

HSETNX key field value sets the value of the field only if the specified field does not exist in the object

HSCAN

HSCAN key cursor [MATCH pattern] [COUNT count] is similar to the SCAN command

Use the example

127.0.0.1 purl 6379 > hset person name jack

(integer) 1

127.0.0.1 6379 > hset person age 20

(integer) 1

127.0.0.1 purl 6379 > hset person sex famale

(integer) 1

127.0.0.1 purl 6379 > hget person name

"jack"

127.0.0.1 purl 6379 > hgetall person

1) "name"

2) "jack"

3) "age"

4) "20"

5) "sex"

6) "famale"

127.0.0.1 purl 6379 > hkeys person

1) "name"

2) "age"

3) "sex"

127.0.0.1 purl 6379 > hvals person

1) "jack"

2) "20"

3) "famale"

4. Set (collection)

It can be understood as a list of non-duplicate values, similar to the concept of sets in the field of mathematics, and Redis also provides operations such as intersection, union, difference and so on.

The internal implementation of set is a HashMap in which value is always null. In fact, the weight is arranged quickly by calculating hash, which is why set can determine whether a member is in the collection or not.

Application scenario

Redis set external function is similar to list is a list function, the special feature is that set can automatically arrange weight, when you need to store a list of data, but do not want to duplicate data, set is a good choice, and set provides an important interface to determine whether a member is in a set collection, which list can not provide.

Or in the Weibo application, where there is a collection of people that each user follows, it is easy to find a common friend of two people.

Related command

SADD

SADD key member [member...] Add one or more elements to the set

SACRD

SCARD key gets the number of elements in the collection

SDIFF

SDIFF key [key...] Get elements that do not exist in the queue

SDIFFSTORE

SDIFFSTORE destination key [key...] Get elements that do not exist in the queue and store them in a key result set

SINTER

SINTER key [key...] Get the intersection of two sets

SINTERSTORE

SINTERSTORE destination key [key...] Get the intersection of two sets and store them in one set

SISMEMBER

SISMEMBER key member determines that a given value is a member of a collection

SMEMBERS

SMEMBERS key gets all the key in the collection

SMOVE

SMOVE source destination member moves one key from a collection to another collection

SPOP

SPOP key [count] gets and deletes elements from a collection

SRANDMEMBER

SRANDMEMBER key [count] randomly fetches an element from the collection

SREM

SREM key member [member...] Delete one or more elements from the collection, and elements that do not exist will be ignored

SUNION

SUNION key [key...] Add multiple set elements

SUNIONSTORE

SUNIONSTORE destination key [key...] Merge set elements and store the results in a new set

SSCAN

SSCAN key cursor [MATCH pattern] [COUNT count] iterates over the elements in set

Use the example

Redis > SADD myset "Hello"

(integer) 1

Redis > SADD myset "World"

(integer) 1

Redis > SMEMBERS myset

1) "World"

2) "Hello"

Redis > SADD myset "one"

(integer) 1

Redis > SISMEMBER myset "one"

(integer) 1

Redis > SISMEMBER myset "two"

(integer) 0

A typical use case for using a collection data structure is the implementation of a friend list:

Redis 127.0.0.1 6379 > sadd friends:leto ghanima paul chani jessica

(integer) 4

Redis 127.0.0.1 6379 > sadd friends:duncan paul jessica alia

(integer) 3

Redis 127.0.0.1 6379 > sismember friends:leto jessica

(integer) 1 # No matter how many friends a user has, we can efficiently (O (1) time complexity) identify whether user X is a friend of user Y.

Redis 127.0.0.1 6379 > sismember friends:leto vladimir

(integer) 0

Redis 127.0.0.1 6379 > sinter friends:leto friends:duncan # We can check whether two or more people have common friends.

1) "paul"

2) "jessica"

Redis 127.0.0.1 redis 6379 > sinterstore friends:leto_duncan friends:leto friends:duncan # can store the result in a new keyword

(integer) 2

5. Sorted Set (ordered set)

Redis ordered collections are similar to Redis collections, except that a function is added, that is, collections are ordered. Each member of an ordered set has a score for sorting.

The time complexity of adding, deleting, and testing Redis ordered sets is all O (1) (fixed time, regardless of the number of sets of elements contained in it). The maximum length of the list is 2 ^ 32-1 elements (4294967295, more than 4 billion sets of each element).

Redis sorted set internal use HashMap and jump table (SkipList) to ensure data storage and order, HashMap is put in the member to score mapping, while the jump table is stored in all the members, sorting according to the score stored in HashMap, the use of jump table structure can achieve higher search efficiency, and relatively simple in implementation.

Working with scen

The usage scenario of Redis sorted set is similar to that of set, except that set is not automatically ordered, while sorted set can sort members by providing an additional parameter of score, and it is inserted in order, that is, automatic sorting. When you need an ordered and non-repeating list of collections, you can choose the sorted set data structure. For example, twitter's public timeline can be stored as a score with the publication time, so that the acquisition is automatically sorted according to time.

For example, the needs of users' points rankings can be realized through orderly collections. There are also lightweight message queues using List described above, which can also be implemented with priority or weighted queues through Sorted Set.

Related command

ZADD

ZADD key score1 member1 [score2 member2] add one or more members to the ordered collection, or update its score if it already exists

ZCARD

The number of ordered set members obtained by ZCARD key

ZCOUNT

ZCOUNT key min max calculates the scores within the range of members and given values of an ordered set

ZINCRBY

ZINCRBY key increment member increases the score of members in an ordered set

ZINTERSTORE

ZINTERSTORE destination numkeys key [key...] Multiple cross-sorted collections are stored to generate a new key ordered set.

ZLEXCOUNT

ZLEXCOUNT key min max calculates the number of ordered set members between a given dictionary range

ZRANGE

ZRANGE key start stop [WITHSCORES] returns an ordered collection of member ranges (from low to high) from the index

ZRANGEBYLEX

ZRANGEBYLEX key min max [LIMIT offset count] returns an ordered collection of member ranges (by dictionary scope)

ZRANGEBYSCORE

ZRANGEBYSCORE key min max [WITHSCORES] [LIMIT] returns all members of the ordered set key whose score values are between min and max (including those equal to min or max). The members of the ordered set are arranged in the order of increasing score values (from smallest to largest).

ZRANK

ZRANK key member determines the ordered set in the index of the member

ZREM

ZREM key member [member...] Remove one or more members from the ordered collection, and members that do not exist will be ignored

ZREMRANGEBYLEX

ZREMRANGEBYLEX key min max deletes the ordered set of all members between a given dictionary range

ZREMRANGEBYRANK

ZREMRANGEBYRANK key start stop deletes an ordered collection of all members within a given index

ZREMRANGEBYSCORE

ZREMRANGEBYSCORE key min max deletes an ordered set of all members within a given score

ZREVRANGE

ZREVRANGE key start stop [WITHSCORES] returns an ordered collection of members, sorted by scores, by index, from high to low

ZREVRANGEBYSCORE

ZREVRANGEBYSCORE key max min [WITHSCORES] returns an ordered collection of member ranges, sorted from highest to lowest in socre

ZREVRANK

ZREVRANK key member determines the index of the members of an ordered collection, sorted by scores, from high to low

ZSCORE

ZSCORE key member gets the scores associated with a given member in an ordered set

ZUNIONSTORE

ZUNIONSTORE destination numkeys key [key...] Add multiple sets to sort, and the resulting sort set is stored in a new key

ZSCAN

ZSCAN key cursor [MATCH pattern] [COUNT count] incremental iterative sorting element set and related scores

Use the example

Redis 127.0.0.1 redis 6379 > zadd dbs 100

(integer) 1

Redis 127.0.0.1 memcached 6379 > zadd dbs 98

(integer) 1

Redis 127.0.0.1 mongodb 6379 > zadd dbs 99

(integer) 1

Redis 127.0.0.1 leveldb 6379 > zadd dbs 99

(integer) 1

Redis 127.0.0.1 6379 > zcard dbs

(integer) 4

Redis 127.0.0.1 6379 > zcount dbs 10 99

(integer) 3

Redis 127.0.0.1 6379 > zrank dbs leveldb

(integer) 1

Redis 127.0.0.1 6379 > zrank dbs other

(nil)

Redis 127.0.1 6379 > zrangebyscore dbs 98 100

1) "memcached"

2) "leveldb"

3) "mongodb"

4) "redis"

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