Will the modified data be updated when it is the same as the original data?

One 、 background

This article mainly tests MySQL perform update When the sentence is , Against the original data （ Not modified ） same update The statement will be in the MySQL Internal re execution ？

Two 、 Test environment

MySQL5.7.25Centos 7.4

3、 ... and 、binlog_format by ROW

1、 Parameters

2、 testing procedure

session1

session2

session1

3、 summary

stay binlog_format=row and binlog_row_image=FULL when , because MySQL Need to be in binlog It records all the fields , So when you read the data, you read all the data , that Duplicate data update Not execute . namely MySQL Called InnoDB The engine provides “ It is amended as follows (1,55)” This interface , But the engine found the same value , Not updated , Go straight back to .

Four 、binlog_format by STATEMENT

1、 Parameters

2、 testing procedure

session1

session2

session1

3、 summary

stay binlog_format=statement and binlog_row_image=FULL when ,InnoDB It's done inside update sentence , namely “ Change this value to (1,999)“ This operation , What should be locked , The update of this update .