Episode 11 of Aiti Tribe Clinic: How to check 30 million data in seconds

【51CTO.com original article】 Activity description : Aiti Tribe is a service community that provides core developers with in-depth technical exchanges, solutions to development needs, and resource sharing. Based on this community, we invite industry technology experts to provide one-on-one breakthroughs on development needs and remove stumbling blocks in the development process. We help developers solve development problems with the most professional and efficient answers.

Topic keywords : Java/MySQL/Server

Tribe lineup : 51CTO community think tank

Object-oriented : Java development engineer, development engineer, PHP development engineer, database development engineer

How to participate : Join the 51CTO developer QQ exchange group (114915964). If you have any technical questions, ask them in the group or send them to the group owner.

Event Details :

.net-james-江西: I would like to ask, how can the online shopping system synchronize the inventory price of goods with the offline ERP purchase, sales and inventory? How to synchronize the product data? Has anyone done this?

Java+Li Sai+Zhengzhou : Make a synchronization program. I have done Java Webservice synchronization before.

Android@鹏@广州: How to optimize MySQL to query 30 million data in seconds? Is there a god-level DBA? Please give me some advice.

 elect agent_product_level ', ' pl ', ' user_id,team_id,create_time,update_time,pl.create_time as apply_time,u.mobile, u.real_name, p.product_name, l.level_name, t.team_name from agent as a 
 
 left join user AS u ON u.user_id = a.user_id 
 
 left join agent_product_level AS pl ON pl.user_id = a.user_id 
 
 left join agent_upgrade AS up ON up.upgrade_id = C:\Users\hexing\AppData\Local\Temp\`7_{~]GF$ 3 {MOQ4V_}PH]YC.png pl.id AND up.disposed = 0   
 
 left join product as p on p.product_id = pl.product_id 
 
 left join agent_level AS l ON l.level_id = pl.level_id 
 
 left join agent_team AS t ON t.team_id = pl.team_id 
 
 limit 100000 , 100 ;

Big Data - Yida - Guangzhou : Your left join cascade is too high. First, make sure that the where condition or condition field to be queried is indexed, so that MySQL can use the index to cover the scan data; second, in multi-table queries, make sure that the join relationship is preferably a large table and a small table filter, that is, make sure to use the data in the small table to filter the large table; finally, optimize the table query statement and modify the complex query to allow the MySQL optimizer to query in a more optimal way.

Java-Small Elements-Yunnan : What is this error? The PHP environment configuration is wrong. G:\myServer\Apache24

 AH00526: Syntax error on line 245 of G:/myServer/Apache24/conf/httpd.conf:
 DocumentRoot must be a directory

Java-木子森-上海: DocumentRoot must be a directory. It probably means that a path is needed but a file is retrieved. I just made some guesses based on the log. Is this prompt caused by insufficient permissions to read a file in your httpd script?

Java-Backend-Yanyu : Why does this address time out when I use idea to build a project? idea2017 version, project generation error, that is, connection timeout.

Java-Neil-Beijing : https://start.spring.io/ Can you open it with your browser? It may be that your network is down. Try to circumvent the firewall and change the local DNS. If that doesn't work, use a VPN tunnel. It may be a problem with your network.

PHP-Shi Xiaojun-Beijing : I would like to ask, what is the problem with using namespaces like this? Fatal error: Class 'Mydb\DB' not found

Half Security-Little Star-Guangzhou : Remove the namespace and debug it, then add it back. It will be more convenient to debug the problem step by step.

PHP-Shi Xiaojun-Beijing : After selecting multiple files, I want to delete one of the pictures. How do I write it?

1>Half Security-Little Star-Guangzhou : Reset, reselect. Or write your own controls, which I personally prefer. Things customized by others/parties have many restrictions

2>Java-So what-Shantou : You can take a look at this. http://www.jq22.com/jquery-info1845

Beijing-Operation and Maintenance-Ugly Duckling : Is this correct? The second location is mainly used to achieve pseudo-static forwarding. Now we need to separate static and dynamic information and distribute pseudo-static matching through proxies, which makes pseudo-static matching difficult.

Back-end interface development - Liu Shengjie - Chengdu : Will url rewriting be possible based on nginx? It depends on your url rules.

Cloud Computing - Cainiao - Suzhou : When viewing files on the desktop in Linux, do I need to enter the specific file location? For example, in my system named bsq, to ​​open the file a in a folder named rrr on the desktop, I should enter cat /home/bsq/Desktop/rrr/a. What's wrong with that?

C++/python-taniey-Beijing : Did you put a space between cat and /? If not, add one.

Network-Kevin-Hebei : What is the difference between rm -rf / and rm -rf /*?

Back-end interface development-Liu Shengjie-Chengdu : It’s the same, both delete all files.

Java-Lauren-Shanghai : I would like to ask, masters, how do you understand and apply the factory pattern in design patterns?

Product-Leon-Shanghai : It can mainly reduce redundancy. The factory class is mainly used to convert the corresponding entity business class. The application scenario is mainly entities at the same level. For example, you may need to use the factory pattern for your various models of smart watches. It is divided into simple factory pattern and abstract factory pattern. The abstract factory pattern will abstract the factory class one more level. Baidu these two design patterns, you should be able to understand them. And they are used in many places.

Beijing-Jingjing-lT : What should I do if the browser keeps showing this error? 360 Browser.

1>Java-Afei-Nanjing : It may be a problem with the https certificate. You can search for the certificate online and download it. I have encountered similar problems before.

2> Cloud Computing - Enwei - Chengdu : If it is Google Chrome, you can ignore it, because Google has long been verifying https websites. Also, if the website certificate is issued by WoSign, it will not work. You can check the certificate of this website to see if the signature has expired.

3>Front-end-Yang Yida-Chengdu : Change to other browsers.

Do you still have questions about these solutions? Welcome to join the 51CTO developer QQ exchange group 114915964 for discussion.

Next event notice: December 19

Keywords: front-end development, Java, database, big data

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