Initial changes to support using udaf min/max for statistics and opti…

[edmondop]

This PR tries to extract some work necessary for #10943. Min and Max are special functions that are used for statistics and optimizations, and they need a special treatment.

[Rafferty97]

Can I suggest using an enum like enum MinMax { Min, Max } instead of a bool?

[jayzhan211]

Here is the code that we need the boolean, maybe name it with is_descending: Option<bool>?

        let (field, desc) = aggr.get_minmax_desc()?;
        if desc != order.options.descending {
            return None;
        }

And, we can get fields separately

[edmondop]

Fixed with eb0ebe0 (#11696) although I am not sure I understood what "is descending" mean for a function?

[jayzhan211]

It is the same idea like descending in SortOptions

pub struct SortOptions {
    /// Whether to sort in descending order
    pub descending: bool,

Would is_sorted_descending: Option<bool> be much more better?

[jayzhan211]

let field = aggr.field()
let is_sorted_descending = aggr.is_sorted_descending()

And, I think getting field and descending separately is better than get_minmax_desc, so if we can get field only if we don't care about descending

[edmondop]

Thanks. The goal of this PR was to simplify #10943 by implementing here the necessary method for udaf, do you think I should proceed in the refactoring now or can we do as a separate improvement?

[jayzhan211]

Not necessary

[jayzhan211]

Thanks @edmondop