Struct datafusion_physical_expr::expressions::StddevPop

pub struct StddevPop { /* private fields */ }

STDDEV_POP population aggregate expression

Implementations

impl StddevPop

pub fn new( expr: Arc<dyn PhysicalExpr>, name: impl Into<String>, data_type: DataType ) -> Self

Create a new STDDEV aggregate function

Trait Implementations

impl AggregateExpr for StddevPop

fn as_any(&self) -> &dyn Any

Return a reference to Any that can be used for downcasting

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

the field of the final result of this aggregation.

fn create_accumulator(&self) -> Result<Box<dyn Accumulator>>

the accumulator used to accumulate values from the expressions. the accumulator expects the same number of arguments as expressions and must return states with the same description as state_fields

fn create_sliding_accumulator(&self) -> Result<Box<dyn Accumulator>>

Creates accumulator implementation that supports retract

fn state_fields(&self) -> Result<Vec<Field>>

the fields that encapsulate the Accumulator’s state the number of fields here equals the number of states that the accumulator contains

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

expressions that are passed to the Accumulator. Single-column aggregations such as sum return a single value, others (e.g. cov) return many.

fn name(&self) -> &str

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

fn row_accumulator_supported(&self) -> bool

If the aggregate expression is supported by row format

fn supports_bounded_execution(&self) -> bool

Specifies whether this aggregate function can run using bounded memory. Any accumulator returning “true” needs to implement retract_batch.

fn create_row_accumulator( &self, _start_index: usize ) -> Result<Box<dyn RowAccumulator>>

RowAccumulator to access/update row-based aggregation state in-place. Currently, row accumulator only supports states of fixed-sized type.

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

Construct an expression that calculates the aggregate in reverse. Typically the “reverse” expression is itself (e.g. SUM, COUNT). For aggregates that do not support calculation in reverse, returns None (which is the default value).

impl Debug for StddevPop

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

Formats the value using the given formatter.