Better documentation on how connection/cursor work

[ZisIsNotZis]

Is your feature request related to a problem?

I'm using aiohttp.web and aiomysql. Before reading the source code, I had no idea weather I should:

• Keep a global cursor and use it
• Keep a global connection and derive a cursor for each request
• Keep a global connection pool and acquire one for each request

Since the traditional "blocking" model uses the third method, and the simple examples given does not use connection pool, I thought method 1 or 2 are also fine.

But after I read the source code, I found that connection is essentially a state machine, and cursor is a “fake” proxy to it. Reusing the same connection at the same time might cause problems. (Correct me if I'm wrong)

Describe the solution you'd like

A better documentation is deserved, especially in README.md, that highlights the importance of using connection pool in concurrent use case.

Describe alternatives you've considered

I'm not sure weather mysql supports pipelining in the same connection (like http pipelining). If it does, maybe cursors can be implemented that way to support concurrent connection reuse?

Additional context

No response

Code of Conduct

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