Redis basic business

Alan.hsiang 2021-01-21 23:52:03
redis basic business


If Redis You need to execute a set of commands , To keep the data consistent , Continuity , You need to use transactions (Transaction), Here are some simple examples , sketch Redis Business related content , For learning and sharing only , If there are shortcomings , Also please correct me .

Redis Business involves command

  • DISCARD: Cancel the business , And DISCARD Is with the MULTI Pairs appear , It can't be used alone .
  • MULTI: Mark the beginning of a transaction block .
  • EXEC: Execute commands in all transactions in sequence .
  • WATCH: Monitor one or more key.
  • UNWATCH: Cancel surveillance .

 

Transaction basic operations

Basic business MULTI Start , With EXEC end , In the middle is a group of Redis command , As shown below :

 1 127.0.0.1:6379> MULTI
 2 OK
 3 127.0.0.1:6379> SET NAME HSIANG
 4 QUEUED
 5 127.0.0.1:6379> SET AGE 20
 6 QUEUED
 7 127.0.0.1:6379> SET SEX MALE
 8 QUEUED
 9 127.0.0.1:6379> SET ADDR SHENZHEN
10 QUEUED
11 127.0.0.1:6379> EXEC
12 1) OK
13 2) OK
14 3) OK
15 4) OK
16 127.0.0.1:6379> 

 

Cancel the business

Cancel the business , Then restore the data to the state before the transaction , With MULTI Start , With DISCARD ending , As shown below :

 1 127.0.0.1:6379> GET AGE
 2 "20"
 3 127.0.0.1:6379> MULTI
 4 OK
 5 127.0.0.1:6379> INCR AGE
 6 QUEUED
 7 127.0.0.1:6379> INCR AGE
 8 QUEUED
 9 127.0.0.1:6379> INCR AGE
10 QUEUED
11 127.0.0.1:6379> DISCARD
12 OK
13 127.0.0.1:6379> GET AGE
14 "20"

 

Transaction partial execution

Redis Transaction , If you want to execute a set of commands , There are no grammatical mistakes , But there is a data type error , It's going on EXEC When , Other commands are executed successfully , Error data execution failed , That's partial success . As shown below :

 1 127.0.0.1:6379> MULTI
 2 OK
 3 127.0.0.1:6379> INCR AGE
 4 QUEUED
 5 127.0.0.1:6379> INCR ADDR
 6 QUEUED
 7 127.0.0.1:6379> INCR AGE
 8 QUEUED
 9 127.0.0.1:6379> EXEC
10 1) (integer) 21
11 2) (error) ERR value is not an integer or out of range
12 3) (integer) 22
13 127.0.0.1:6379> GET AGE
14 "22"

 

Transaction terminated

If it's to be done Redis command , There are grammatical errors , It's going on EXEC When you roll back , As shown below :

 1 127.0.0.1:6379> MULTI
 2 OK
 3 127.0.0.1:6379> INCR AGE
 4 QUEUED
 5 127.0.0.1:6379> SET ADDR
 6 (error) ERR wrong number of arguments for 'set' command
 7 127.0.0.1:6379> INCR AGE
 8 QUEUED
 9 127.0.0.1:6379> EXEC
10 (error) EXECABORT Transaction discarded because of previous errors.
11 127.0.0.1:6379> GET AGE
12 "22"

Redis lock

Lock is divided into optimistic lock , Pessimistic locking , Here are the introduction :

  • Pessimistic locking (Pessimistic Lock): As its name suggests , With strong exclusivity and exclusivity . It refers to the data being exposed to the outside world ( Includes other current transactions of the system , And transactions from external systems ) The revision was conservative .
  • Optimism lock (Optimistic Locking): It's a relative pessimistic lock , Optimistic locks assume that the data will not cause conflicts in general , So when the data is submitted for update , The data conflict will be formally detected or not , If there is a conflict , Then return the error information to the user , Let the user decide how to do it . Optimistic lock is suitable for scenarios with many read operations , This can improve the throughput of the program .

WATCH monitor

When monitoring key The value of changed before the transaction , The transaction is not executed . Only after the monitoring is cancelled , The transaction is executed , As shown below :

 1 127.0.0.1:6379> WATCH balance
 2 OK
 3 127.0.0.1:6379> set balance 300
 4 OK
 5 127.0.0.1:6379> MULTI
 6 OK
 7 127.0.0.1:6379> INCRBY balance 10
 8 QUEUED
 9 127.0.0.1:6379> DECRBY debt 10
10 QUEUED
11 127.0.0.1:6379> EXEC
12 (nil)
13 127.0.0.1:6379> GET balance
14 "300"
15 127.0.0.1:6379> UNWATCH
16 OK

Redis The nature of transactions

  1. Separate isolation operation : All commands in the transaction , Will be serialized , Execute in order . The transaction is in progress , Will not be interrupted by other command requests .
  2. There is no concept of isolation level : Commands in the queue , Before submission , None of them are actually executed , There is no internal transaction to view the updates in the transaction .
  3. There is no guarantee of atomicity :redis In the same business , If a command fails , Other commands will be executed , No rollback ( Unlike relational databases ).

remarks

Early onset Baidicheng

author : Li Bai ( Tang Dynasty )

Leaving at dawn the White King crowned with rainbow cloud , I have sailed a thousand miles through Three Georges in a day .

With monkeys' sad adieus the riverbanks are loud , My boat has left ten thought mountains far away .

版权声明
本文为[Alan.hsiang]所创,转载请带上原文链接,感谢
https://javamana.com/2021/01/20210121232959338D.html

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