Struct datafusion_expr::AggregateUDF

pub struct AggregateUDF { /* private fields */ }

Logical representation of a user-defined aggregate function (UDAF).

An aggregate function combines the values from multiple input rows into a single output “aggregate” (summary) row. It is different from a scalar function because it is stateful across batches. User defined aggregate functions can be used as normal SQL aggregate functions (GROUP BY clause) as well as window functions (OVER clause).

AggregateUDF provides DataFusion the information needed to plan and call aggregate functions, including name, type information, and a factory function to create Accumulator, which peform the actual aggregation.

For more information, please see the examples.

Implementations

impl AggregateUDF

pub fn new( name: &str, signature: &Signature, return_type: &ReturnTypeFunction, accumulator: &AccumulatorFactoryFunction, state_type: &StateTypeFunction ) -> Self

Create a new AggregateUDF

pub fn call(&self, args: Vec<Expr>) -> Expr

creates an Expr that calls the aggregate function.

This utility allows using the UDAF without requiring access to the registry, such as with the DataFrame API.

pub fn name(&self) -> &str

Returns this function’s name

pub fn signature(&self) -> &Signature

Returns this function’s signature (what input types are accepted)

pub fn return_type(&self, args: &[DataType]) -> Result<DataType>

Return the type of the function given its input types

pub fn accumulator( &self, return_type: &DataType ) -> Result<Box<dyn Accumulator>>

Return an accumualator the given aggregate, given its return datatype.

pub fn state_type(&self, return_type: &DataType) -> Result<Vec<DataType>>

Return the type of the intermediate state used by this aggregator, given its return datatype. Supports multi-phase aggregations

Trait Implementations

impl Clone for AggregateUDF

fn clone(&self) -> AggregateUDF

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for AggregateUDF

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

Formats the value using the given formatter.

impl Hash for AggregateUDF

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for AggregateUDF

fn eq(&self, other: &Self) -> 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.

impl Eq for AggregateUDF