Method get_parameter_names

datafusion/expr/src/logical_plan/plan.rs:1590–1603

Walk the logical plan, find any `Placeholder` tokens, and return a set of their names.

(&self)

    /// Walk the logical plan, find any `Placeholder` tokens, and return a set of their names.
    pub fn get_parameter_names(&self) -> Result<HashSet<String>> {
        let mut param_names = HashSet::new();
        self.apply_with_subqueries(|plan| {
            plan.apply_expressions(|expr| {
                expr.apply(|expr| {
                    if let Expr::Placeholder(Placeholder { id, .. }) = expr {
                        param_names.insert(id.clone());
                    }
                    Ok(TreeNodeRecursion::Continue)
                })
            })
        })
        .map(|_| param_names)
    }

    /// Walk the logical plan, find any `Placeholder` tokens, and return a map of their IDs and DataTypes
    ///