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https://www.codermast.com/database/redis/five-base-datatype.htmlillustrate
In our usual business, we basically only use the basic data types of Redis (String, List, Hash, Set, Sorted Set), and the special types (Geo, Bitmap, Hyperloglog) are only used in special business scenarios. Usually, we only need to master the basic data types, and the special types can be understood.
# String string
String type, that is, string type, is the simplest storage type in Redis. The String type is binary safe. It means that the String of redis can contain any data. Such as jpg images or serialized objects.
Its value is a string, but according to the format of the string, it can be divided into three categories:
- string: ordinary string
- int: Integer type, can do self-increment and self-decrement operations
- float: Floating point type, can do self-increment and self-decrement operations
Regardless of the format, the bottom layer is stored in the form of a byte array, but the encoding method is different. The maximum space of string type cannot exceed 512m.
Common operation commands of String type :
| Order | describe |
|---|---|
| SET | Add or modify an existing key-value pair of String type |
| GET | Get the value of String type according to the key |
| MSET | Add multiple key-value pairs of String type in batches |
| MGET | Get multiple values of String type according to multiple keys |
| INCR | Increment an integer key by 1 |
| INCRBY | Let an integer key auto-increment and specify the step size, for example: incrby num 2 let the num value auto-increment by 2 |
| INCRBYFLOAT | Increment a floating-point number with a specified step size |
| SETNX | Add a key-value pair of String type, provided that the key does not exist, otherwise it will not execute |
| SEVEN | Add a key-value pair of String type and specify the validity period |
Although there is no directory structure in the key of Redis, multiple words are allowed to form a hierarchical structure, and multiple words are separated by ":". Generally, the format used is: 项目名:业务名:类型:id.
This format is not fixed, you can also delete or add entries according to your own needs.
for example
For example, our project name is myblog, and there are two different types of data, user and product. We can define the key like this:
User related key: myblog:user:1
Product related key: myblog:product:1
If Value is a Java object, such as a User object, you can serialize the object into a JSON string and store it
| KEY | VALUE |
|---|---|
| myblog:user:1 | {“id”:1, “name”: “Jack”, “age”: 21} |
| myblog:product:1 | {"id":1, "name": "Xiaomi 11", "price": 4999} |
# Hash hash
Hash type, also called hash, can also become hash type. Its value is an unordered dictionary, similar to the HashMap structure in Java.
The Hash structure can store each field in the object independently, and can do CRUD for a single field
Hash type data
Common commands for Hash are:
| Order | describe |
|---|---|
| HSET key field value | Add or modify the value of the field of the hash type key |
| HGET key field | Get the field value of a hash type key |
| HMSET | hmset and hset have the same effect, hmset can be discarded after 4.0 |
| HMGET | Get the field values of multiple hash type keys in batches |
| HGETALL | Get all fields and values in a hash type key |
| HKEYS | Get all the fields in a hash type key |
| WHALES | Get all the values in a hash type key |
| HINCRBY | Let the field value of a hash type key auto-increment and specify the step size |
| HSETNX | Add a field value of a hash type key, provided that the field does not exist, otherwise it will not be executed |
# List list
The List type in Redis is similar to the LinkedList in Java, which can be regarded as a doubly linked list structure. Both forward search and reverse search can be supported.
Traits are also similar to LinkedList:
- orderly
- elements can be repeated
- Fast insertion and deletion
- General query speed
It is often used to store an ordered data, for example: friend circle like list, comment list, etc.
| Order | describe |
|---|---|
| LPUSH key element … | Insert one or more elements to the left of the list |
| LPOP key | Remove and return the first element on the left of the list, or nil if there is no |
| RPUSH key element … | Insert one or more elements to the right of the list |
| RPOP key | Remove and return the first element on the right side of the list |
| LRANGE key star end | Returns all elements within a subscript range |
| BLPOP and BRPOP | Similar to LPOP and RPOP, except that it waits for the specified time when there are no elements, instead of returning nil directly |
Schematic diagram of a double-ended queue
# Set collection
The Set structure of Redis is similar to the HashSet in Java, which can be regarded as a HashMap whose value is null. Because it is also a hash table, it has similar characteristics to HashSet
- out of order
- Elements cannot be repeated
- find fast
- Support intersection, union, difference and other functions
| Order | describe |
|---|---|
| SADD key member … | Add one or more elements to the set |
| SREM key member | Remove the specified element in the set |
| SCARD key | Returns the number of elements in the set |
| SISMEMBER key member | Determine whether an element exists in the set |
| SMEMBERS | Get all elements in the set |
| SINTER key1 key2 … | Find the intersection of key1 and key2 |
| SDIFF key1 key2 … | Find the difference between key1 and key2 |
| SUNION key1 key2 … | Find the union of key1 and key2 |
tip Intersection, difference, and union diagrams
# SortedSet ordered collection
Redis's SortedSet can also be called Zset, which is a sortable set collection, which is somewhat similar to TreeSet in Java, but the underlying data structure is very different.
Each element in the SortedSet has a score attribute, and the elements can be sorted based on the score attribute. The underlying implementation is a skip list (SkipList) plus a hash table.
SortedSet has the following characteristics:
- sortable
- elements are not repeated
- query speed
Because of the sortable nature of SortedSet, it is often used to implement functions such as leaderboards.
Common commands for SortedSet are
| Order | describe |
|---|---|
| ZADD key score member | Add one or more elements to the sorted set, and update its score value if it already exists |
| ZREM key member | Delete a specified element in the sorted set |
| ZSCORE key member | Get the score value of the specified element in the sorted set |
| ZRANK key member | Get the rank of the specified element in the sorted set |
| ZCARD key | Get the number of elements in the sorted set |
| ZCOUNT key min max | Count the number of all elements whose score value is within a given range |
| ZINCRBY key increment member | Make the specified elements in the sorted set self-increment, and the step size is the specified increment value |
| ZRANGE key min max | After sorting by score, get the elements within the specified ranking range |
| ZRANGEBYSCORE key min max | After sorting by score, get the elements within the specified score range |
| ZDIFF、ZINTER、ZUNION | Find difference, intersection, union |
Notice
All rankings are in ascending order by default. If you want to order in descending order, you REVcan add it after Z in the command.