Trait PhysicalExpr 

pub trait PhysicalExpr: Send + Sync {
    // Required methods
    fn evaluate_impl(
        &self,
        df: &DataFrame,
        _state: &ExecutionState,
    ) -> PolarsResult<Column>;
    fn evaluate_on_groups_impl<'a>(
        &self,
        df: &DataFrame,
        groups: &'a GroupPositions,
        state: &ExecutionState,
    ) -> PolarsResult<AggregationContext<'a>>;
    fn to_field(&self, input_schema: &Schema) -> PolarsResult<Field>;
    fn is_scalar(&self) -> bool;

    // Provided methods
    fn as_expression(&self) -> Option<&Expr> { ... }
    fn as_column(&self) -> Option<PlSmallStr> { ... }
    fn evaluate(
        &self,
        df: &DataFrame,
        state: &ExecutionState,
    ) -> PolarsResult<Column> { ... }
    fn evaluate_on_groups<'a>(
        &self,
        df: &DataFrame,
        groups: &'a GroupPositions,
        state: &ExecutionState,
    ) -> PolarsResult<AggregationContext<'a>> { ... }
    fn is_literal(&self) -> bool { ... }
}

Take a DataFrame and evaluate the expressions. Implement this for Column, lt, eq, etc

Required Methods

fn evaluate_impl( &self, df: &DataFrame, _state: &ExecutionState, ) -> PolarsResult<Column>

fn evaluate_on_groups_impl<'a>( &self, df: &DataFrame, groups: &'a GroupPositions, state: &ExecutionState, ) -> PolarsResult<AggregationContext<'a>>

fn to_field(&self, input_schema: &Schema) -> PolarsResult<Field>

Get the output field of this expr

fn is_scalar(&self) -> bool

Provided Methods

fn as_expression(&self) -> Option<&Expr>

fn as_column(&self) -> Option<PlSmallStr>

fn evaluate( &self, df: &DataFrame, state: &ExecutionState, ) -> PolarsResult<Column>

Take a DataFrame and evaluate the expression.

Note: implementers should implement evaluate_impl instead, as this wraps that call with an error context.

fn evaluate_on_groups<'a>( &self, df: &DataFrame, groups: &'a GroupPositions, state: &ExecutionState, ) -> PolarsResult<AggregationContext<'a>>

Some expression that are not aggregations can be done per group Think of sort, slice, filter, shift, etc. defaults to ignoring the group

This method is called by an aggregation function.

In case of a simple expr, like ‘column’, the groups are ignored and the column is returned. In case of an expr where group behavior makes sense, this method is called. For a filter operation for instance, a Series is created per groups and filtered.

An implementation of this method may apply an aggregation on the groups only. For instance on a shift, the groups are first aggregated to a ListChunked and the shift is applied per group. The implementation then has to return the Series exploded (because a later aggregation will use the group tuples to aggregate). The group tuples also have to be updated, because aggregation to a list sorts the exploded Series by group.

This has some gotcha’s. An implementation may also change the group tuples instead of the Series.

fn is_literal(&self) -> bool

Trait Implementations

impl Display for &dyn PhysicalExpr

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

Formats the value using the given formatter.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors