Function grouping_set_to_exprlist

datafusion/expr/src/utils.rs:257–272

Find all distinct exprs in a list of group by expressions. If the first element is a `GroupingSet` expression then it must be the only expr.

(group_expr: &[Expr])

/// Find all distinct exprs in a list of group by expressions. If the
/// first element is a `GroupingSet` expression then it must be the only expr.
pub fn grouping_set_to_exprlist(group_expr: &[Expr]) -> Result<Vec<&Expr>> {
    if let Some(Expr::GroupingSet(grouping_set)) = group_expr.first() {
        if group_expr.len() > 1 {
            return plan_err!(
                "Invalid group by expressions, GroupingSet must be the only expression"
            );
        }
        Ok(grouping_set.distinct_expr())
    } else {
        Ok(group_expr
            .iter()
            .collect::<IndexSet<_>>()
            .into_iter()
            .collect())
    }
}

/// Recursively walk an expression tree, collecting the unique set of columns
/// referenced in the expression