Method add_column_refs

datafusion/expr/src/expr.rs:2070–2078

Adds references to all columns in this expression to the set See [`Self::column_refs`] for details

(&'a self, set: &mut HashSet<&'a Column>)

    ///
    /// See [`Self::column_refs`] for details
    pub fn add_column_refs<'a>(&'a self, set: &mut HashSet<&'a Column>) {
        self.apply(|expr| {
            if let Expr::Column(col) = expr {
                set.insert(col);
            }
            Ok(TreeNodeRecursion::Continue)
        })
        .expect("traversal is infallible");
    }

    /// Return all references to columns and their occurrence counts in the expression.
    ///