MySQL field truncation principle and source code analysis

background

I met a very Weird The problem of , The data just inserted , The next time I checked, I couldn't find . After investigation, the database truncated the data we need to insert .

The screening process

Pull the front end line by line debug, Compare data entered into database , It is found that the database can be inserted successfully . So I found some information on the Internet

Positioning and problem solving

Finally, I contacted dba, yes sql_mode What a mess

follow-up

In order to thoroughly understand what is going on , So I picked it up mysql Source code , decision debug And reappear next

Source code

Install the source code environment

Reference resources

https://www.jianshu.com/p/a88ea5558f87

Mysql-5.7.23 , jb- clion , cmake,boost

Tool name	effect
Mysql-5.7.23	mysql Source code
jb- clion	ide
cmake	c,c++ Installation and compilation tools for
boost	c++ Extension library for , Similar to some three parties jar

Environmental Science

Mysql-5.7.23 jb- clion

CREATE TABLE `test` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(10) DEFAULT '',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=75 DEFAULT CHARSET=utf8mb4;

Strict mode

Default configuration is good

Verify that strict mode is enabled

Key code

Field_longstr::report_if_important_data

Nonstrict mode

Modify the configuration

Key code

Suggest

 In the insertion of key fields , need check Information such as the length of the field , Or some key values are generated by the backend , And then it goes back to the front end 

frequently-used sql_mode

sqol_mode	explain
ONLY_FULL_GROUP_BY	about GROUP BY Aggregation operation , If in SELECT Column in , Not in the GROUP BY It appears that , So this SQL It's illegal , Because the list is not in GROUP BY In the clause
NO_AUTO_VALUE_ON_ZERO	This value affects the insertion of self growing columns . By default , Insert 0 or NULL Represents the generation of the next self increasing value . If the user wants to insert a value of 0, And the column is self-growing , So this option works .
STRICT_TRANS_TABLES	If a value cannot be inserted into a transaction , Then interrupt the current operation , No restrictions on non transaction tables
NO_ZERO_IN_DATE	Zero days and months are not allowed
NO_ZERO_DATE	mysql Database is not allowed to insert zero date , Inserting a zero date throws an error instead of a warning
ERROR_FOR_DIVISION_BY_ZERO	stay insert or update In the process , If the data is divided by zero , It's a mistake, not a warning . If the mode is not given , So when the data is divided by zero Mysql return NULL
NO_AUTO_CREATE_USER	prohibit GRANT Create a user with a blank password
NO_ENGINE_SUBSTITUTION	If the required storage engine is disabled or not compiled , Then throw an error . When this value is not set , Replace... With the default storage engine , And throw an exception
PIPES_AS_CONCAT	take "||" Treat as the concatenation operator of a string, not as the or operator , This sum Oracle The database is the same , And string concatenation function Concat Think similar
ANSI_QUOTES	You can't use double quotes to refer to strings , Because it's interpreted as an identifier