Struct datafusion::physical_plan::expressions::Count

pub struct Count { /* private fields */ }

COUNT aggregate expression Returns the amount of non-null values of the given expression.

Implementations

impl Count

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

Create a new COUNT aggregate function.

pub fn new_with_multiple_exprs( exprs: Vec<Arc<dyn PhysicalExpr>>, name: impl Into<String>, data_type: DataType ) -> Count

Trait Implementations

impl AggregateExpr for Count

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

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

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

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

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 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).

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

Creates accumulator implementation that supports retract

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

Return a specialized GroupsAccumulator that manages state for all groups.

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

impl Clone for Count

fn clone(&self) -> Count

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Count

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

Formats the value using the given formatter.

impl PartialEq<dyn Any> for Count

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.