Any way to cartesian product two futures_channel::mpsc::Receiver?

[GallYang]

I tried existed posts, and found solutions for iterators, seems not solutions to my problem;
Currently, I tried collect one receiver and pop the other receiver to create production;
Seems a waste of time to wait collect end;
Any suggections for me?
Here is the code snippet

        let CartesianProductExecutor {
            mut output,
            input_left,
            mut input_right,
        } = *self;

        let left = input_left.collect::<Vec<_>>().await;
        while let Some(row) = input_right.next().await {
            for l in left.iter() {
                let mut row = row.clone();
                row.extend(l.to_owned());
                output.send(row).await?;
            }
        }

[2e71828]

Fundamentally, you’ll need to keep O(n) of state information in order to calculate the Cartesian product— That means something like Vec.

If you need the rows in the usual order, there’s no way to avoid consuming all of one channel before returning the first result. If the output order doesn’t matter to you, though, you can write a streaming version:

• Initialize 2 empty Vecs 𝓁 and 𝓇
• For every item 𝓍 to arrive from either input channel (via select or similar):
  • If the item came from the left channel
    • For every item 𝓎 in 𝓇, yield (𝓍, 𝓎)
    • Push 𝓍 onto 𝓁
  • If the item came from the right channel
    • For every item 𝓎 in 𝓁, yield (𝓎, 𝓍)
    • Push 𝓍 onto 𝓇

[GallYang]

Thank you for your advice, seems it's already the best solution for me.