Method map_children

datafusion/expr/src/tree_node.rs:124–350

Maps each child of `self` using the provided closure `f`. The closure `f` takes ownership of an expression and returns a `Transformed` result, indicating whether the expression was transformed or left unchanged.

(
        self,
        f: F,
    )

    /// The closure `f` takes ownership of an expression and returns a `Transformed` result,
    /// indicating whether the expression was transformed or left unchanged.
    fn map_children<F: FnMut(Self) -> Result<Transformed<Self>>>(
        self,
        f: F,
    ) -> Result<Transformed<Self>> {
        Ok(match self {
            // TODO: remove the next line after `Expr::Wildcard` is removed
            #[expect(deprecated)]
            Expr::Column(_)
            | Expr::Wildcard { .. }
            | Expr::Placeholder(Placeholder { .. })
            | Expr::OuterReferenceColumn(_, _)
            | Expr::Exists { .. }
            | Expr::ScalarSubquery(_)
            | Expr::ScalarVariable(_, _)
            | Expr::Literal(_, _)
            | Expr::LambdaVariable(_) => Transformed::no(self),
            Expr::SetComparison(SetComparison {
                expr,
                subquery,
                op,
                quantifier,
            }) => expr.map_elements(f)?.update_data(|expr| {
                Expr::SetComparison(SetComparison {
                    expr,
                    subquery,
                    op,
                    quantifier,
                })
            }),
            Expr::Unnest(Unnest { expr, .. }) => expr
                .map_elements(f)?
                .update_data(|expr| Expr::Unnest(Unnest { expr })),
            Expr::Alias(Alias {
                expr,
                relation,
                name,
                metadata,
            }) => expr.map_elements(f)?.update_data(|expr| {
                Expr::Alias(Alias {
                    expr,
                    relation,
                    name,
                    metadata,
                })
            }),
            Expr::InSubquery(InSubquery {
                expr,
                subquery,
                negated,
            }) => expr.map_elements(f)?.update_data(|be| {
                Expr::InSubquery(InSubquery::new(be, subquery, negated))
            }),
            Expr::BinaryExpr(BinaryExpr { left, op, right }) => (left, right)
                .map_elements(f)?
                .update_data(|(new_left, new_right)| {
                    Expr::BinaryExpr(BinaryExpr::new(new_left, op, new_right))
                }),
            Expr::Like(Like {