Struct datafusion::physical_expr::expressions::Stddev

pub struct Stddev { /* private fields */ }

STDDEV and STDDEV_SAMP (standard deviation) aggregate expression

Implementations

impl Stddev

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

Create a new STDDEV aggregate function

Trait Implementations

impl AggregateExpr for Stddev

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 this aggregation.

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

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, Global>, DataFusionError>

Creates accumulator implementation that supports retract

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

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, Global>, Global>

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 order_bys(&self) -> Option<&[PhysicalSortExpr]>

Order by requirements for the aggregate function By default it is None (there is no requirement) Order-sensitive aggregators, such as FIRST_VALUE(x ORDER BY y) should implement this

fn groups_accumulator_supported(&self) -> bool

If the aggregate expression has a specialized GroupsAccumulator implementation. If this returns true, [Self::create_groups_accumulator] will be called.

fn create_groups_accumulator( &self ) -> Result<Box<dyn GroupsAccumulator, Global>, DataFusionError>

Return a specialized GroupsAccumulator that manages state for all groups.

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

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 Stddev

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

Formats the value using the given formatter.

impl PartialEq<dyn Any> for Stddev

fn eq(&self, other: &(dyn Any + 'static)) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.