[BEAM-12626] Side inputs with Session windows are not populated

• Type: Bug
• Status: Resolved
• Priority: P2
• Resolution: Fixed
• Fix Version/s: 2.33.0
• Component/s: sdk-py-core
• Assignee: Ahmet Altay
• Reporter: Ahmet Altay
• Created: 16/Jul/21 03:14
• Updated: 16/Jul/21 03:19
• Resolved: 16/Jul/21 03:19

Description

In the following pipeline, side input values are always empty:

windowed = (
    p
    | beam.Create([('k', 1), ('k', 2), ('k', 20)])
    | beam.MapTuple(
        lambda k, v: beam.transforms.window.TimestampedValue((k, v), v))
    | beam.WindowInto(beam.transforms.window.Sessions(10)))

windowed | beam.Map(lambda k, si: (k, si), beam.pvalue.AsIter(windowed))

The problem does not happen with FixedWindows, and in Java similarly formed pipelines (side input with Sessions windows) are rejected (https://github.com/apache/beam/blob/8463a054c1d7e2b7ee8d11e9569e065cb5e02196/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/windowing/Sessions.java#L97)

Issue Links

• links to: GitHub Pull Request #15173