Trait datafusion::logical_plan::ExpressionVisitor

pub trait ExpressionVisitor<E = Expr> where
    E: ExprVisitable, {
    fn pre_visit(self, expr: &E) -> Result<Recursion<Self>, DataFusionError>
    where
        Self: ExpressionVisitor<Expr>;

    fn post_visit(self, _expr: &E) -> Result<Self, DataFusionError> { ... }
}

Encode the traversal of an expression tree. When passed to Expr::accept, ExpressionVisitor::visit is invoked recursively on all nodes of an expression tree. See the comments on Expr::accept for details on its use

Required Methods

fn pre_visit(self, expr: &E) -> Result<Recursion<Self>, DataFusionError> where
    Self: ExpressionVisitor<Expr>, 

Invoked before any children of expr are visisted.

Provided Methods

fn post_visit(self, _expr: &E) -> Result<Self, DataFusionError>

Invoked after all children of expr are visited. Default implementation does nothing.

Implementors