Enum Answers 

pub enum Answers {
    Rows,
    Count,
    Aggregate(Box<Aggregate>),
}

What a body wanted from a group, which decides whether the group has to be built at all.

docs/99 §99.9 item 6: an aggregate that builds the collection in order to measure it has done the work the question was avoiding. All of these are recognised from the same filter_list — bare, or wrapped in the question the program asked of it — which is why they are a field of one variant rather than several shapes.

Variants

Rows

The rows. filter_list(…) on its own, whose value is a list.

Count

How many rows. list_len(filter_list(…)), whose value is an Int — and no list is built.

Aggregate(Box<Aggregate>)

A number the group’s rows decide, which the group does not have to exist for. list_min(filter_list(…)) or list_sum(…), or either over a map_list of it — and no list is built.

Boxed because it is the only variant carrying an expression, and an enum is as large as its largest arm wherever it is held.

Trait Implementations

impl Clone for Answers

fn clone(&self) -> Answers

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Answers

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.