Architecture overview may be insufficient in README

[xudong963]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
Now I'm working hard on this project.

Describe the solution you'd like
After I am familiar with datafusion, I will provide a more detailed architecture overview.
Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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