Replication of variables in golang concurrency

Recently golang Programming language development , Deeply realized golang The convenience of language parallelism , But it also brings some small problems ,

No big problem , Let's solve . Let's first look at what concurrency is .

What is parallel ？ What is concurrency ？

• The key to parallelism is that you can do many things at the same time , There are many common parallel computers , Multicore parallelism ; Concurrency is managing a lot of things at the same time , These things can be carried out within the specified time .
• Concurrency focuses on avoiding blocking , So that the program will not stop because of blocking ; Parallelism is dependent on hardware and operating system resources .
• Concurrency lies in structure , Parallelism lies in executing . The application has a good concurrent structure , The operating system can make better use of hardware parallel execution , Dispatch reasonably , promote CPU utilization .

golang in , We all talk about parallel , Try to tap the potential of the machine , Take full advantage of the multi-core nature of the machine , Make code execution most efficient .

golang The built-in functions of the language are used in parallel go , Let's start a collaborative process . This process is called goroutine

What is? goroutine？

goroutine Is a lightweight abstraction based on threads . stay Go In language , When a function is created as goroutine when ,Go Think of it as a separate unit of work , And it can execute multiple in parallel at a very low cost goroutine.

say , Today's problem ,

I'm in a loop , Set up a group goroutinue , Each coroutine executes a function , In this function ,

func (s *ServiceImpl) getData(
	ctx context.Context,
	aa int64,
	where []string,
) (data Data,err error) {
	queryWhere := where
	

I found that every request has a problem ,

Ten pieces of data will be queried each time , But every time you assemble SQL All have problems , There is a problem SQL It's also random .

So I print the log in the code to see ,

Find log output , It turned out to be normal

This is strange , Add a line of code for logging ,

Remove Log code , Another problem 100% Reappear .

Finally, various search problems , Suddenly found that ,queryWhere It's a slice ,

It is still a matter of basic knowledge ,golang in slice At the bottom is an array , And it is a reusable array ,

Change the code to

func (s *ServiceImpl) getData(
	ctx context.Context,
	aa int64,
	where []string,
) (data Data,err error) {
	queryWhere := make([]string, len(where))
	copy(queryWhere, where）

Do not add log statements , The problem has also been solved .

We still have to lay more foundation