org.apache.beam.sdk.extensions.sql.udf

Interface AggregateFn<InputT,AccumT,OutputT>

Type Parameters:

InputT - type of input values

AccumT - type of mutable accumulator values

OutputT - type of output values

All Known Implementing Classes:

UdfTestProvider.Sum

public interface AggregateFn<InputT,AccumT,OutputT>

An aggregate function that can be executed as part of a SQL query.

AggregateFn contains a subset of the functionality of org.apache.beam.sdk.transforms.Combine.CombineFn.

AggregateFn is experimental. Compatibility is not guaranteed across Beam versions.

Method Summary

Modifier and Type	Method and Description
AccumT	addInput(AccumT mutableAccumulator, InputT input) Adds the given input value to the given accumulator, returning the new accumulator value.
AccumT	createAccumulator() Returns a new, mutable accumulator value, representing the accumulation of zero input values.
OutputT	extractOutput(AccumT mutableAccumulator) Returns the output value that is the result of combining all the input values represented by the given accumulator.
AccumT	mergeAccumulators(AccumT mutableAccumulator, java.lang.Iterable<AccumT> immutableAccumulators) Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.

Method Detail

createAccumulator

AccumT createAccumulator()

Returns a new, mutable accumulator value, representing the accumulation of zero input values.

addInput

AccumT addInput(AccumT mutableAccumulator,
                InputT input)

Adds the given input value to the given accumulator, returning the new accumulator value.

Parameters:

mutableAccumulator - may be modified and returned for efficiency

input - should not be mutated

mergeAccumulators

AccumT mergeAccumulators(AccumT mutableAccumulator,
                         java.lang.Iterable<AccumT> immutableAccumulators)

Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.

Parameters:

mutableAccumulator - This accumulator may be modified and returned for efficiency.

immutableAccumulators - These other accumulators should not be mutated, because they may be shared with other code and mutating them could lead to incorrect results or data corruption.

extractOutput

OutputT extractOutput(AccumT mutableAccumulator)

Returns the output value that is the result of combining all the input values represented by the given accumulator.

Parameters:

mutableAccumulator - can be modified for efficiency