Struct datafusion::physical_plan::expressions::NthValue

pub struct NthValue { /* private fields */ }

nth_value expression

Implementations

impl NthValue

pub fn first( name: impl Into<String>, expr: Arc<dyn PhysicalExpr>, data_type: DataType, ignore_nulls: bool ) -> NthValue

Create a new FIRST_VALUE window aggregate function

pub fn last( name: impl Into<String>, expr: Arc<dyn PhysicalExpr>, data_type: DataType, ignore_nulls: bool ) -> NthValue

Create a new LAST_VALUE window aggregate function

pub fn nth( name: impl Into<String>, expr: Arc<dyn PhysicalExpr>, data_type: DataType, n: i64, ignore_nulls: bool ) -> Result<NthValue, DataFusionError>

Create a new NTH_VALUE window aggregate function

pub fn get_kind(&self) -> NthValueKind

Get the NTH_VALUE kind

Trait Implementations

impl BuiltInWindowFunctionExpr for NthValue

fn as_any(&self) -> &(dyn Any + 'static)

Return a reference to Any that can be used for downcasting

fn field(&self) -> Result<Field, DataFusionError>

The field of the final result of evaluating this window function.

fn expressions(&self) -> Vec<Arc<dyn PhysicalExpr>>

Expressions that are passed to the PartitionEvaluator.

fn name(&self) -> &str

Human readable name such as "MIN(c2)" or "RANK()". The default implementation returns placeholder text.

fn create_evaluator( &self ) -> Result<Box<dyn PartitionEvaluator>, DataFusionError>

Create a PartitionEvaluator for evaluating the function on a particular partition.

fn reverse_expr(&self) -> Option<Arc<dyn BuiltInWindowFunctionExpr>>

Construct a new BuiltInWindowFunctionExpr that produces the same result as this function on a window with reverse order. The return value of this function is used by the DataFusion optimizer to avoid re-sorting the data when possible.

fn evaluate_args( &self, batch: &RecordBatch ) -> Result<Vec<Arc<dyn Array>>, DataFusionError>

Evaluate window function’s arguments against the input window batch and return an ArrayRef.

fn get_result_ordering(&self, _schema: &Arc<Schema>) -> Option<PhysicalSortExpr>

Returns the ordering introduced by the window function, if applicable. Most window functions don’t introduce an ordering, hence the default value is None. Note that this information is used to update ordering equivalences.

impl Debug for NthValue

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

Formats the value using the given formatter.