Function powerset

datafusion/expr/src/utils.rs:103–111

The [power set] (or powerset) of a set S is the set of all subsets of S, \ including the empty set and S itself. Example: If S is the set {x, y, z}, then all the subsets of S are \ {} \ {x} \ {y} \ {z} \ {x, y} \ {x, z} \ {y, z} \ {x, y, z} \ and hence the power set of S is {{}, {x}, {y}, {z}, {x, y}, {x, z}, {y, z}, {x, y, z}}. [power set]: https://en.wikipedia.org/wiki/Power_set

(slice: &[T])

///
/// [power set]: https://en.wikipedia.org/wiki/Power_set
pub fn powerset<T>(slice: &[T]) -> Result<Vec<Vec<&T>>> {
    if slice.len() >= 64 {
        return plan_err!("The size of the set must be less than 64");
    }

    Ok(powerset_indices(slice.len())
        .map(|indices| indices.iter().map(|&idx| &slice[idx]).collect())
        .collect())
}

/// check the number of expressions contained in the grouping_set
fn check_grouping_set_size_limit(size: usize) -> Result<()> {