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This article introduces the knowledge of "the execution process of InnoDB engine in mysql". Many people will encounter this dilemma in the operation of actual cases. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1. Stored in bufferpool.

When the executor gets the sql that needs to be executed, it needs to load the data that needs to be modified from disk into memory according to the update condition.

2. Back up the data before modifying it.

Put the data into the undolog to facilitate the operation when the transaction is rolled back.

The sql statement modifies the corresponding value in memory.

Write redologbuffer according to the modified data.

3. Write down the redolog content.

For this step, see the configuration of innodb_flush_at_trx_commit. Generally, it is written to the system cache first, and then written to the system file by the operating system DMA asynchronous operation. The flush operation only writes the data in the system memory to the buffer of the operating system, and the data reading and writing is usually done by the kernel thread. This step is to convert the data from the user thread to the kernel thread for operation. When reading and writing files, there will be a multi-level cache between disk files and memory to improve the efficiency of data exchange. That's what oscache does here.

4. Binlog write operation.

5. Write to oscache.

Brush the operating system into the disk file. As shown in the figure, the configuration of sync_log. Generally speaking, innodb_flush_at_trx_commit and sync_log are configured to 1.

6. Commit the transaction.

When the data is written to disk, InnoDB writes the data twice.

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