Struct datafusion::physical_expr::equivalence::ProjectionMapping

pub struct ProjectionMapping {
    pub map: Vec<(Arc<dyn PhysicalExpr>, Arc<dyn PhysicalExpr>)>,
}

Stores the mapping between source expressions and target expressions for a projection.

Fields

map: Vec<(Arc<dyn PhysicalExpr>, Arc<dyn PhysicalExpr>)>

Mapping between source expressions and target expressions. Vector indices correspond to the indices after projection.

Implementations

impl ProjectionMapping

pub fn try_new( expr: &[(Arc<dyn PhysicalExpr>, String)], input_schema: &Arc<Schema> ) -> Result<ProjectionMapping, DataFusionError>

Constructs the mapping between a projection’s input and output expressions.

For example, given the input projection expressions (a + b, c + d) and an output schema with two columns "c + d" and "a + b", the projection mapping would be:

 [0]: (c + d, col("c + d"))
 [1]: (a + b, col("a + b"))

where col("c + d") means the column named "c + d".

pub fn iter( &self ) -> impl Iterator<Item = &(Arc<dyn PhysicalExpr>, Arc<dyn PhysicalExpr>)>

Iterate over pairs of (source, target) expressions

pub fn target_expr( &self, expr: &Arc<dyn PhysicalExpr> ) -> Option<Arc<dyn PhysicalExpr>>

This function returns the target expression for a given source expression.

Arguments

• expr - Source physical expression.

Returns

An Option containing the target for the given source expression, where a None value means that expr is not inside the mapping.

Trait Implementations

impl Clone for ProjectionMapping

fn clone(&self) -> ProjectionMapping

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ProjectionMapping

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

Formats the value using the given formatter.