Add example for writing an SQL analysis pass about arrow-datafusion HOT 3 OPEN

I like the Join count analysis, I had to do this in my project (mentioned in #10808) in a really hacky way. We can have 2 sorts of counts:

1. Count every individual join
2. Count all groups of joins (subsequent joins that are related) with their respective count(this would have been useful for me)

I do have a question.
How can we show these results? Because Analyzer rules only return transformed LogicalPlans, or do I understand something in a wrong way?

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Thank you @LorrensP-2158466 -- sorry for the delay . I have been traveling

I do have a question.
How can we show these results? Because Analyzer rules only return transformed LogicalPlans, or do I understand something in a wrong way?

I think in an example, we can use println! which is what we do in other examples:

Normally the idea is to give a well documented example that shows the basic pattern that people can start with

For this one, maybe you could show how to use TreeNode::apply to walk the tree. Something like (totally untested)

let mut join_count = 0;
plan.apply(|child| {
  if matches!(child, LogicalPlan::Join(_)) {
    join_count += 1;
  }
});

println!("Found {join_count} joins in the plan");

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Thanks for the reply!

That's exactly what I have made, I'll open up a PR later today or tomorrow.

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