Struct FirstValueAggregator 

pub struct FirstValueAggregator { /* private fields */ }

FIRST_VALUE aggregator - returns the first value seen in a window.

Tracks the value with the earliest timestamp in the window. For deterministic results, uses event timestamp, not arrival order.

Example

use laminar_core::operator::window::FirstValueAggregator;

// Track first price by timestamp
let first_price = FirstValueAggregator::new(0, 1); // price col 0, timestamp col 1

Implementations

impl FirstValueAggregator

pub fn new(value_column_index: usize, timestamp_column_index: usize) -> Self

Creates a new FIRST_VALUE aggregator.

Arguments

• value_column_index - Column to extract value from
• timestamp_column_index - Column for event timestamp ordering

Trait Implementations

impl Aggregator for FirstValueAggregator

type Acc = FirstValueAccumulator

The accumulator type used by this aggregator.

fn create_accumulator(&self) -> FirstValueAccumulator

Creates a new empty accumulator.

fn extract(&self, event: &Event) -> Option<(i64, i64)>

Extracts a value from an event to be aggregated.

fn output_data_type(&self) -> DataType

Returns the Arrow [DataType] for this aggregator’s output.

fn output_nullable(&self) -> bool

Returns whether the output is nullable (e.g., empty windows produce null).

fn extract_batch( &self, event: &Event, ) -> SmallVec<[<Self::Acc as Accumulator>::Input; 4]>

Extracts all values from a multi-row batch event.

impl Clone for FirstValueAggregator

fn clone(&self) -> FirstValueAggregator

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FirstValueAggregator

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

Formats the value using the given formatter.