Function string_agg

src/expr/src/relation/func.rs:239–273

(datums: I, temp_storage: &'a RowArena, order_by: &[ColumnOrder])

}

fn string_agg<'a, I>(datums: I, temp_storage: &'a RowArena, order_by: &[ColumnOrder]) -> Datum<'a>
where
    I: IntoIterator<Item = Datum<'a>>,
{
    const EMPTY_SEP: &str = "";

    let datums = order_aggregate_datums(datums, order_by);
    let mut sep_value_pairs = datums.into_iter().filter_map(|d| {
        if d.is_null() {
            return None;
        }
        let mut value_sep = d.unwrap_list().iter();
        match (value_sep.next().unwrap(), value_sep.next().unwrap()) {
            (Datum::Null, _) => None,
            (Datum::String(val), Datum::Null) => Some((EMPTY_SEP, val)),
            (Datum::String(val), Datum::String(sep)) => Some((sep, val)),
            _ => unreachable!(),
        }
    });

    let mut s = String::default();
    match sep_value_pairs.next() {
        // First value not prefixed by its separator
        Some((_, value)) => s.push_str(value),
        // If no non-null values sent, return NULL.
        None => return Datum::Null,
    }

    for (sep, value) in sep_value_pairs {
        s.push_str(sep);
        s.push_str(value);
    }

    Datum::String(temp_storage.push_string(s))
}

fn jsonb_agg<'a, I>(datums: I, temp_storage: &'a RowArena, order_by: &[ColumnOrder]) -> Datum<'a>
where