Bufferpool caching mechanism for executing SQL in MySQL

One 、MySQL Bottom structure diagram

Two 、MySQL Logging and caching mechanism

After watching MySQL The underlying structure diagram of , Many people may have such questions ：
Why? MySQL You can't directly update the data on the disk, and set up such a complex mechanism to execute SQL Well ？

Because if every request is directly to MySQL Read and write data files , It's random IO, For each read and write , All mechanical hard disks have seek time and rotation delay , Therefore, the performance of directly updating data disk files is relatively low , For SSDs , You also need to determine the read and write location through the address translation mechanism , Therefore, directly updating disk files cannot make the database resist high concurrency .
MySQL This mechanism looks complex , But it can ensure that every update request is to update memory BufferPool, Then write log files sequentially , At the same time, it can also ensure the data consistency under various abnormal conditions . The performance of updating memory and writing log files on disk sequentially is very high , Much higher than random reading and writing disk files .

1. binlog： It belongs to MySQL Server Layer log file , It is mainly used to recover database data .
2. undo log：InnoDB Engine specific log files , It is mainly used to recover when a transaction is rolled back Buffer Pool Data in cache pool .
3. redo log：InnoDB Engine specific log files , It is mainly used to recover after system downtime and restart Buffer Pool Data that has not been written to the disk in the cache pool .