Trait datafusion_expr::UserDefinedLogicalNode

pub trait UserDefinedLogicalNode: Debug + Send + Sync {
    // Required methods
    fn as_any(&self) -> &dyn Any;
    fn inputs(&self) -> Vec<&LogicalPlan> ;
    fn schema(&self) -> &DFSchemaRef;
    fn expressions(&self) -> Vec<Expr> ;
    fn fmt_for_explain(&self, f: &mut Formatter<'_>) -> Result;
    fn from_template(
        &self,
        exprs: &[Expr],
        inputs: &[LogicalPlan]
    ) -> Arc<dyn UserDefinedLogicalNode>;

    // Provided method
    fn prevent_predicate_push_down_columns(&self) -> HashSet<String> { ... }
}

This defines the interface for LogicalPlan nodes that can be used to extend DataFusion with custom relational operators.

See the example in user_defined_plan.rs for an example of how to use this extension API

Required Methods

fn as_any(&self) -> &dyn Any

Return a reference to self as Any, to support dynamic downcasting

fn inputs(&self) -> Vec<&LogicalPlan>

Return the logical plan’s inputs

fn schema(&self) -> &DFSchemaRef

Return the output schema of this logical plan node

fn expressions(&self) -> Vec<Expr>

returns all expressions in the current logical plan node. This should not include expressions of any inputs (aka non-recursively) These expressions are used for optimizer passes and rewrites.

fn fmt_for_explain(&self, f: &mut Formatter<'_>) -> Result

Write a single line, human readable string to f for use in explain plan

For example: TopK: k=10

fn from_template( &self, exprs: &[Expr], inputs: &[LogicalPlan] ) -> Arc<dyn UserDefinedLogicalNode>

Create a new ExtensionPlanNode with the specified children and expressions. This function is used during optimization when the plan is being rewritten and a new instance of the ExtensionPlanNode must be created.

Note that exprs and inputs are in the same order as the result of self.inputs and self.exprs.

So, `self.from_template(exprs, ..).expressions() == exprs

Provided Methods

fn prevent_predicate_push_down_columns(&self) -> HashSet<String>

A list of output columns (e.g. the names of columns in self.schema()) for which predicates can not be pushed below this node without changing the output.

By default, this returns all columns and thus prevents any predicates from being pushed below this node.

Implementors