discussion: use order_float instead of f32,f64

[ZENOTME]

To support partition write, we need something like HashMap<StructValue,_>. So this means that we need to impl Eq for AnyValue. To do this, we need to replace f32, f64 to order_float. (e.g. https://crates.io/crates/ordered-float)

As https://internals.rust-lang.org/t/f32-f64-should-implement-hash/5436/33#:~:text=If%20you%20want%20to%20have%20a%20content%20hash%20of%20a%20struct%20that%20includes%20floats says, to support Hash for the struct, we also can use serde. But I guess there may be other scenes we need Eq.

[ZENOTME]

cc @liurenjie1024 @Xuanwo

[Xuanwo]

I'm open with using order_float. But here are some edge cases to take care:

• The order: spec said we need to use -NaN < -Infinity < -value < -0 < 0 < value < Infinity < NaN.
• The hash: iceberg has hash specs for float value that: hashLong(doubleToLongBits(double(v))

Maybe we should do something extra here instead of store StructValue in hashmap directly.

[liurenjie1024]

I'm open with using order_float. But here are some edge cases to take care:

• The order: spec said we need to use -NaN < -Infinity < -value < -0 < 0 < value < Infinity < NaN.
• The hash: iceberg has hash specs for float value that: hashLong(doubleToLongBits(double(v))

Maybe we should do something extra here instead of store StructValue in hashmap directly.

We may need to implement customized ordering trait, hash function.

[ZENOTME]

There are two problem in https://crates.io/crates/ordered-float

1. -0 == +0
2. it don't have concept of -nan

I guess the only solve way is to maintain our own ordered_float.

[Xuanwo]

I guess the only solve way is to maintain our own ordered_float.

Maybe it's easier to implement Hash and Eq by our own.

[ZENOTME]

Maybe it's easier to implement Hash and Eq by our own.

Do you means that implement the custom behaviour in PrimitiveValue🤔, like

impl<T: Float> Ord for PrimitiveValue<T> {
    fn cmp(&self, other: &Self) -> Ordering {
        match (self,other) => {
            (Float(l),Float(r)) => {
                // custom behaviour
            }
        } 
    }
}

[liurenjie1024]

Do you means that implement the custom behaviour in PrimitiveValue🤔, like

LGTM.