Method distinct_expr

datafusion/expr/src/expr.rs:1431–1446

Return all distinct exprs in the grouping set. For `CUBE` and `ROLLUP` this is just the underlying list of exprs. For `GROUPING SET` we need to deduplicate the exprs in the underlying sets.

(&self)

    /// is just the underlying list of exprs. For `GROUPING SET` we need to deduplicate
    /// the exprs in the underlying sets.
    pub fn distinct_expr(&self) -> Vec<&Expr> {
        match self {
            GroupingSet::Rollup(exprs) | GroupingSet::Cube(exprs) => {
                exprs.iter().collect()
            }
            GroupingSet::GroupingSets(groups) => {
                let mut exprs: Vec<&Expr> = vec![];
                for exp in groups.iter().flatten() {
                    if !exprs.contains(&exp) {
                        exprs.push(exp);
                    }
                }
                exprs
            }
        }
    }
}

/// A Lambda expression with a set of parameters names and a body