[native_datafusion] [Spark SQL Tests] Streaming self-union returns no results

[andygrove]

Description

When running Spark SQL tests with native_datafusion scan enabled, two streaming self-union tests in StreamingSelfUnionSuite fail because the streaming query result is None instead of containing the expected data.

Failing Tests

• self-union, DSv1, read via DataStreamReader API
• self-union, DSv1, read via table API

Error

Assert on query failed: : None was empty

Context

Found during CI run: https://github.com/apache/datafusion-comet/actions/runs/21691646806/job/62552819424?pr=3393