MySQL Subversion learning record: User Recharge function Realization (a): When the server stuck 7 seconds what happened 11

Source: Internet
Author: User

1. First create two tables, fill the Log table (User_balance_log), User Balance table (user_balance)
The table structure is as follows:
(1) User_balance:

(2) User_balance_log:

Note: The Log_type log Type 1 represents a 2 on behalf of the consumer 3 for the transfer


2. Write stored procedure to simulate user recharge

BEGIN
#Routine body goes here ...
DECLARE t_error int default 0;
DECLARE usercount int default 0;
Declare CONTINUE HANDLER for SQLEXCEPTION set t_error=1; #当发生错误时, set to 1

Start TRANSACTION;
#插入用户充值日志表
Insert into User_balance_log (User_id,log_type,log_des,log_value) values (_user_id,_log_type,_log_des,_log_value);

If Row_count () >0 then #插入成功
Select COUNT (*) into UserCount from user_balance where user_id = _user_id;
If UserCount > 0 Then #用户存在
Update user_balance set user_money=user_money+_log_value where user_id=_user_id;
Else
Insert into user_balance (User_id,user_money) values (_user_id,_log_value);
End If;
End If;


Select Sleep (7), ' End of Lag ';


If T_error=1 Then
ROLLBACK;
Else
COMMIT;
End If;

END

Note: parameters in _user_id int,in _log_type tinyint,in _log_des varchar ($), in _log_value decimal (10,2)

3. Execute the Stored procedure

Call Sp_add_usermoney (3,1, ' User recharge ', 10);

After the execution 5 times, the User Charge Log table (User_balance_log) is as follows,

The User Balance table (user_balance) is as follows: That is, the execution of five stored procedures, each recharge 10 yuan, accumulated 5 times is 50 yuan.

4. Analog Lag

Simulate the system to stutter for 7 seconds before commit, as follows:

Select Sleep (7), ' End of Lag ';

Executes a stored procedure once, then opens another session, executes

This results in the following:

(1) The user is charged on duty log table:

(2) User Balance table:

At this point, the user Balance table inserts two rows of data from the same user_id. Since the system is stuck, the operation to insert data in the stored procedure is not committed and the data is inserted in another session, which creates a problem.

MySQL Subversion learning record: User Recharge function Realization (a): When the server stuck 7 seconds what happened 11

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.