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This article mainly explains "what are the basic data structures and operations of Redis". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what basic data structures and operations does Redis have".

Basic structure

The maximum upper limit of key and value for a String type is 512m. Its basic structure is as follows: basic grammar

The basic operation of strings in Redis is shown in the following table.

Usage scenario-count the number of days users are online

Bitmap is very effective for certain types of calculations.

Suppose we now want to record the frequency of users on our site, for example, calculating how many days user A has been online, how many days user B has been online, and so on, as data to determine which users should participate in activities such as beta testing-a pattern that can be implemented using SETBIT and BITCOUNT.

For example, whenever a user goes online on a certain day, we use SETBIT, take the user name as the key, take the launch date of the website represented on that day as the offset parameter, and set the offset to 1.

For example, if today is the 100th day of the launch of the site, and user peter has read the site today, execute the command SETBIT peter 101; if peter continues to read the site tomorrow, execute the command SETBIT peter 1001, and so on.

When you want to calculate the total number of times peter has been online, use the BITCOUNT command: execute BITCOUNT peter, and the result is the total number of days peter has been online.

Basic structure

Operation syntax description BLPOPBLPOP key [key...] TimeoutBLPOP is the blocking pop-up primitive of a list. It is a blocking version of the LPOP command, and when there are no elements available to pop up in a given list, the connection is blocked by the BLPOP command. BRPOPBRPOP key [key...] Timeout is the blocking version of the RPOP command, and the connection will be blocked by the BRPOP command when there are no elements available to pop up in the given list. BRPOPLPUSHBRPOPLPUSH source destination timeoutBRPOPLPUSH is the blocking version of RPOPLPUSH, and BRPOPLPUSH behaves like RPOPLPUSH when the given list source is not empty. When the list source is empty, the BRPOPLPUSH command blocks the connection until the wait times out, or until another client executes the LPUSH or RPUSH command on the source. LINDEXLINDEX key index returns the element in the list key with the subscript index. LINSERTLINSERT key BEFORE/AFTER pivot value inserts the value value into the list key, before or after the value pivot. When pivot does not exist in the list key, no action is performed. When key does not exist, key is treated as an empty list and no action is performed. If key is not a list type, an error is returned. LLENLLEN key returns the length of the list key. LPOPLPOP key removes and returns the header element of the list key. LPUSHLPUSH key value [value...] Insert one or more values value into the header of the list key LPUSHXLPUSHX key value inserts the value value into the header of the list key if and only if key exists and is a list LRANGELRANGE key start stop returns elements within the specified interval in the list key, the interval specifies LREMLREM key count value according to the value of the parameter count by offset start and stop Remove the element equal to the parameter value in the list LSETLSET key index value sets the value of the element in the list key subscript index to valueLTRIMLTRIM key start stop to trim a list, that is, let the list retain only the elements within the specified range, and all elements that are not within the specified range will be deleted. For example, executing the command LTRIM list 0 2 means that only the first three elements of the list list are retained, and all the remaining elements are deleted. RPOPRPOP key removes and returns the tail element of the list key the RPOPLPUSHRPOPLPUSH source destination command RPOPLPUSH performs the following two actions in an atomic time: pop up the last element (the tail element) in the list source and return it to the client. Insert the source pop-up element into the list destination as the header element of the destination list. RPUSHRPUSH key value [value...] Insert one or more values value into the footer of the list key (rightmost) RPUSHXRPUSHX key value inserts the value value into the footer of the list key if and only if key exists and is a list. In contrast to the RPUSH command, the RPUSHX command does nothing when key does not exist.

To give some examples:

Stack

127.0.0.1 rpop stack 6379 > lpush stack "a"b"c" (integer) 3 127.0.0.1 rpop stack "a" 123 4

Queue

127.0.0.1 lpush queue 6379 > lpop queue "a"b"c" (integer) 3 127.0.0.1 lpop queue "c" 123 4 5

BLPOP

127.0.0.1 exists job 6379 > blpop job 5 # blocking until 5s timeout (nil) (5.03s) 12 3 4 5

LINDEX

127.0.1 lpush myjob "my"job"is"iter" (integer) 4 127.0.1 iter 6379 > lindex myjob-1 "my" 123 43 3. Hash table Hash

What is stored is a mapping table of field and value, that is, a Map is stored, each piece of data can be regarded as key-field-value format, and field-value corresponds to a key-value pair of Map.

Basic grammar

Usage scenarios-storing social relationships

For example, Sina's follow list and fan list are all implemented by hash.

Basic structure

Operation syntax description SADDSADD key member [member...] If one or more member elements are added to the collection key, member elements that already exist in the collection will be ignored. SCARDSCARD key returns the cardinality of the collection key (the number of elements in the collection). SDIFFSDIFF key [key...] Returns all members of a collection that is the difference between all given collections. SDIFFSTORESDIFFSTORE destination key [key...] This command works similar to SDIFF, except that it saves the results to the destination collection instead of simply returning the result set. SINTERSINTER key [key...] Returns all members of a collection that is the intersection of all given collections. SINTERSTORESINTERSTORE destination key [key...] This command is similar to the SINTER command, but it saves the result to the destination collection instead of simply returning the result set. SISMEMBERSISMEMBER key member determines whether the member element is a member of the collection key. SMEMBERSSMEMBERS key returns all members of the collection key. SMOVESMOVE source destination member moves the member element from the source collection to the destination collection. SPOPSPOP key removes and returns a random element in the collection. SRANDMEMBERSRANDMEMBER key [count] if count is positive and less than the cardinality of the set Then the command returns an array of count elements, each of which is different. If count is greater than or equal to the cardinality of the collection, the entire collection is returned. If count is negative, the command returns an array in which elements may be repeated multiple times, and the length of the array is the absolute value of count. SREMSREM key member [member...] Remove one or more member elements from the collection key, and non-existent member elements are ignored. SUNIONSUNION key [key...] Returns all members of a collection that is the union of all given collections. SUNIONSTORESUNIONSTORE destination key [key...] This command is similar to the SUNION command, but it saves the result to the destination collection instead of simply returning the result set. For more information on SSCANSSCAN key cursor [MATCH pattern] [COUNT count], please refer to the SCAN command.

Give me some examples.

Difference set

127.0.1 sadd set1 "A1"a2"a3" (integer) 3 127.0.1 "a3" (integer) 3 127.0.0.1 "a4" (integer) 3 127.0.0.1 sdiff set1 set2 1) "a2" 127.0.0.1 > sdiffstore set set1 set2 (integer) 1 127.0.1 > smembers set1) "a2" 1 2 3 4 5 6 7 8 9 10 11

Union set

127.0.0.1 sadd set1 6379 > sadd set2 "A1"a2"a3" (integer) 3 127.0.1 "A3"a4" (integer) 3 127.0.0.1 6379 > sunion set1 set2 1) "a4" 2) "A1" 3) "a3" 4) "a2" 12 3 4 5 6 7 8 9 10

Intersection

127.0.0.1 sadd set1 "A1"a2"a3" (integer) 3 127.0.0.1 sadd set2 "A1"a3"a4" (integer) 3 127.0.0.16379 > smembers set1) "a2" 127.0.0.16379 > sinter set1 set2 1) "A3" 2) "A1" 127.0.0.1 > sinterstore set set1 set2 (integer) 2 127.0.0.1: 6379 > smembers set 1) "A1" 2) "A3" 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 5. Ordered set SortedSet

Like set, sorted set is also a collection of elements of type string, except that each element is associated with a score of type double, so sorted set is an ordered collection.

Basic grammar

Usage scenarios-ranking of user scores

Compared with Sets, Sorted Sets adds a weight parameter score to the elements in Set, so that the elements in the collection can be arranged in order by score, such as a Sorted Sets that stores the scores of the whole class, whose collection value can be the student number of students, and score can be its examination score, so that when the data is inserted into the collection, it has been sorted naturally. In addition, Sorted Sets can be used to make weighted queues, such as the score of ordinary messages is 1 and the score of important messages is 2, and then the worker thread can choose to get work tasks in reverse order of score. Give priority to important tasks.

An element with weight, such as a game's ranking of user scores

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