groupedWeighted

Accumulate incoming events until the combined weight of elements is greater than or equal to the minimum weight and then pass the collection of elements downstream.

Simple operators

Signature

Source.groupedWeightedSource.groupedWeighted Flow.groupedWeightedFlow.groupedWeighted

Description

Chunk up this stream into groups of elements that have a cumulative weight greater than or equal to the minWeight, with the last group possibly smaller than requested minWeight due to end-of-stream.

See also:

  • grouped for a variant that groups based on number of elements
  • groupedWithin for a variant that groups based on number of elements and a time window
  • groupedWeightedWithin for a variant that groups based on element weight and a time window

Examples

The below example demonstrates how groupedWeighted groups the accumulated elements into Seq List and maps with other operation.

Scala
val collections = immutable.Iterable(Seq(1, 2), Seq(3, 4), Seq(5, 6))
Source[Seq[Int]](collections).groupedWeighted(4)(_.length).runForeach(println)
// Vector(Seq(1, 2), Seq(3, 4))
// Vector(Seq(5, 6))

Source[Seq[Int]](collections).groupedWeighted(3)(_.length).runForeach(println)
// Vector(Seq(1, 2), Seq(3, 4))
// Vector(Seq(5, 6))
Java
Source.from(Arrays.asList(Arrays.asList(1, 2), Arrays.asList(3, 4), Arrays.asList(5, 6)))
    .groupedWeighted(4, x -> (long) x.size())
    .runForeach(System.out::println, system);
// [[1, 2], [3, 4]]
// [[5, 6]]

Source.from(Arrays.asList(Arrays.asList(1, 2), Arrays.asList(3, 4), Arrays.asList(5, 6)))
    .groupedWeighted(3, x -> (long) x.size())
    .runForeach(System.out::println, system);
// [[1, 2], [3, 4]]
// [[5, 6]]

Reactive Streams semantics

emits when the cumulative weight of elements is greater than or equal to the minimum weight or upstream completed

backpressures when a group has been assembled and downstream backpressures

completes when upstream completes

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