Function count

src/expr/src/relation/func.rs:195–211

(datums: I)

}

fn count<'a, I>(datums: I) -> Datum<'a>
where
    I: IntoIterator<Item = (Datum<'a>, Diff)>,
{
    // Count is accumulable: rather than expand each `(datum, diff)` into `diff`
    // copies and count them, we sum the diffs directly. A net-negative count is
    // possible (the surface does not define behavior in that case) and surfaces
    // here as a negative result.
    // TODO(jkosh44) This should error when the count can't fit inside of an `i64` instead of returning a negative result.
    let mut count = Diff::ZERO;
    for (datum, diff) in datums {
        if !datum.is_null() {
            count += diff;
        }
    }
    Datum::from(count.into_inner())
}

fn any<'a, I>(datums: I) -> Datum<'a>
where