core/org.jetbrains.kotlinx.dataframe.impl.aggregation.aggregators.aggregationHandlers/ReducingAggregationHandler

ReducingAggregationHandler

internal class ReducingAggregationHandler<in Value : Any, out Return>(val reducer: Reducer<Value, Return>, val getReturnType: CalculateReturnType) : AggregatorAggregationHandler<Value, Return>

Implementation of AggregatorAggregationHandler which functions like a reducer: it takes a sequence of values and returns a single value, which can be a completely different type.

Parameters

reducer

This function actually does the reduction. Before it is called, nulls are filtered out. The type of the values is passed as KType to the reducer.

getReturnType

This function must be supplied to give the return type of reducer given some input type and whether the input is empty.

Constructors

ReducingAggregationHandler

constructor(reducer: Reducer<Value, Return>, getReturnType: CalculateReturnType)

Properties

aggregator

open override var aggregator: Aggregator<Value, Return>?

Reference to the aggregator instance.

getReturnType

val getReturnType: CalculateReturnType

reducer

val reducer: Reducer<Value, Return>

Functions

aggregateSequence

open override fun aggregateSequence(values: Sequence<Value?>, valueType: ValueType): Return

Base function of Aggregator.

aggregateSingleColumn

open fun aggregateSingleColumn(column: DataColumn<Value?>): Return

Aggregates the data in the given column and computes a single resulting value. Calls aggregateSequence. It tries to exploit a cache for statistics which can be accessed by ValueColumnInternal

calculateReturnType

open override fun calculateReturnType(valueType: KType, emptyInput: Boolean): KType

Give the return type of reducer given some input type and whether the input is empty. Calls the supplied getReturnType.

indexOfAggregationResultSingleSequence

open override fun indexOfAggregationResultSingleSequence(values: Sequence<Value?>, valueType: ValueType): Int

This function always returns -1 because the result of a reducer is not in the input values.

init

open fun init(aggregator: Aggregator<Value, Return>)

ReducingAggregationHandler

Parameters

See also

Constructors

Properties

Functions