Rewrite UDAF reversed expression name

[jayzhan211]

          I think it would be good to eventually move this to a method in `https://github.com/apache/datafusion/pull/11611` though I agree this is good for now. Maybe we can file a ticket to track

Originally posted by @alamb in #11611 (comment)

I think we could extend to rewrite the whole expression name, and it could be more straightforward what the name is rewritten

                let mut name = self.name().to_string();
                // If the function is changed, we need to reverse order_by clause as well
                // i.e. First(a order by b asc null first) -> Last(a order by b desc null last)
                if self.fun().name() == reverse_udf.name() {
                } else {
                    replace_order_by_clause(&mut name);
                }
                replace_fn_name_clause(&mut name, self.fun.name(), reverse_udf.name());

Something like

let mut name = self.name().to_string();
name = self.fun.reverse_name(name)

Add reverse_name in AggregateUDFImpl

trait AggregateUDFImpl {
    fn reverse_name(&self) -> String {
        ...
    }
}

Specificially we need to rewrite name for First/Last. For array_agg, the name should be the same.

[dharanad]

take

[dharanad]

I plan to close this by 10th Aug. I hope that okay ? Feel free to re assign if this is a priority

[dharanad]

Apologies for the delay here. Somehow i missed this. @jayzhan211 I went through the conversation and somewhat understood the issue. But for better clarity can you share more info here. Once again sorry, for the delay here.

[jayzhan211]

What you need to do is, add a new method reverse_name

trait AggregateUDFImpl {
    fn reverse_name(&self) -> String {
        ...
    }
}

Replace with the code here

                let mut name = self.name().to_string();
                // If the function is changed, we need to reverse order_by clause as well
                // i.e. First(a order by b asc null first) -> Last(a order by b desc null last)
                if self.fun().name() == reverse_udf.name() {
                } else {
                    replace_order_by_clause(&mut name);
                }
                replace_fn_name_clause(&mut name, self.fun.name(), reverse_udf.name());

if the function name is changed (i.e. First -> Last), order by clause required to rewrite too