Add ApplyOrder::Recursive to replace None: Option<ApplyOrder> and remove nested pattern matching.

[HaoYang670]

Currently, we use None to represent an optimizing rule to be recursively applied to its children.
And we use Some(TopDown) and Some(BottomUp) to represent a rule can be directly applied to the child node.

The None usage can be directly replaced by introducing a new product type ApplyOrder::Recursive.
This can

• remove the usage of nested pattern matching,
• better comment the code ,
• and help the rust compiler to better optimize the code.

This is a follow-up of #4618.

Describe the solution you'd like

pub enum ApplyOrder {
     /// ...
    TopDown,
    /// ...
    BottomUp,
    /// ...
    Recursive,
}

Describe alternatives you've considered
We could not do this.

Additional context
Add any other context or screenshots about the feature request here.

[HaoYang670]

Hi @jackwener, I have one question about the optimize_node function:

    fn optimize_node(
        &self,
        rule: &Arc<dyn OptimizerRule + Send + Sync>,
        plan: &LogicalPlan,
        config: &dyn OptimizerConfig,
    ) -> Result<Option<LogicalPlan>> {
        // TODO: future feature: We can do Batch optimize
        rule.try_optimize(plan, config)
    }

Does it only optimize the top level plan node or the whole plan tree?
I don't understand the difference between it and the try_optimize.

[HaoYang670]

And I am currently confused about the implementation difference between Some(ApplyOrder::TopDown) and None. Both of them call the try_optimize in the function optimize_recursively.

[jackwener]

Does it only optimize the top level plan node or the whole plan tree? I don't understand the difference between it and the try_optimize.

We can do batch optimize in one plannode

 rules: Vec<rule>
for rule in rules {
    rule.try_optimize(plan, config)
}

[jackwener]

And I am currently confused about the implementation difference between Some(ApplyOrder::TopDown) and None. Both of them call the try_optimize in the function optimize_recursively.

When use None, try_optimize is just entry (it just use for top plannode), the internal implementation (topdown/bottomup) is inside rule.