Overview of redis/mysql knowledge

One 、 database

Two 、Redis

1、Redis summary

Redis It's completely open source and free , Is a high-performance key-value database .

Reference resources

2、Redis Reasons for fast speed

3、Redis data type

Redis Five data types are supported ：string（ character string ）,hash（ Hash ）,list（ list ）,set（ aggregate ） And zset sorted set： Ordered set ).

4、Redis Persistence mechanism of

Redis There are two persistence mechanisms RDB and AOF Mechanism :

RDB(Redis DataBase) Persistence mode ： It refers to the semi persistent mode of data set snapshot , Record redis All key value pairs of database , Write data to a temporary file at a certain point in time , After persistence , Replace the last persisted file with this temporary file , Achieve data recovery .

advantage ：
（1） Only one file dump.rdb, Easy persistence .
（2） Good disaster tolerance , A file can be saved to a safe disk .
（3） Maximize performance ,fork Sub process to complete the write operation , Let the main process continue processing commands , So it is IO Maximize . Use a single child process for persistence , The main process will not do anything IO operation , To ensure the redis A high performance .
（4） When the data set is large , Than AOF It's more efficient to start .

shortcoming ：
Data security is low .RDB It's persistence at intervals , If between persistence redis failure , There will be data loss . So this way is more suitable when the data requirements are not rigorous .

AOF(Append-only file) Persistence mode ： Means all command line records to redis Command please The format of the protocol is fully persistent ) Save as aof file .

advantage ：
1） Data security ,aof Persistence can be configured appendfsync attribute , Yes always, Every command operation is recorded as aof Once in the file .
2） adopt append Mode write file , Even if the server goes down , Can pass redis-check-aof Tools for data consistency .
3）AOF The mechanism rewrite Pattern .AOF The document was not rewrite Before （ When the file is too large, the command will be merged and rewritten ）, You can delete some of these commands （ For example, misoperation flushall）)
shortcoming ：
1）AOF File than RDB The file is big , And the recovery speed is slow .
2） When the data set is large , Than rdb Low starting efficiency .

5、Redis Partition

6、Redis cache

7、Redis Business

1） A transaction is a separate isolation operation ： All commands in the transaction are serialized 、 To execute in order .
Transaction is in the process of execution , Will not be interrupted by command requests from other clients .
2） A transaction is an atomic operation ： The commands in the transaction are either all executed , Or none of it .

8、Redis colony

9 、Redis A single thread ？

Reference resources

10、Redis Elimination strategy

3、 ... and 、Mysql

1、Mysql summary

2、 Database operation

Reference resources

3、 Table operations

Create table

Modify table

4、Mysql function

5、 Table data operation

6、 engine

7、 Business

8、 Data import and export

9、 Classic interview questions