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

Interface AggregateFn<InputT extends @Nullable Object,AccumT extends @Nullable Object,OutputT extends @Nullable Object>

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 extends @Nullable Object,AccumT extends @Nullable Object,OutputT extends @Nullable Object>
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.

  • Method Summary

    Modifier and Type
    Method
    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, Iterable<AccumT> immutableAccumulators)
    Returns an accumulator representing the accumulation of all the input values accumulated in the merging accumulators.

  • Method Details

    • 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, 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