`GroupedHashAggregateStream::emit` throws ArrowError: column types must match schema types

[hsiang-c]

Describe the bug

While testing DataFusion Comet, we found that DataFusion throws an exception:

ArrowError: column types must match schema types,
  expected List(Struct("colA": Boolean, ...))
  but found  List(Struct("colA": non-null Boolean, ...))  at column index 1

and the corresponding call stack is GroupedHashAggregateStream::emit() ← spill() ← try_update_memory_reservation()

Also raised the issue in Comet: apache/datafusion-comet#5239

To Reproduce

No response

Expected behavior

No response

Additional context

No response

[alamb]

This looks like a regression to me so adding to the release

• Release DataFusion 55.0.0 (Jul / Aug 2026) #22393

FYI @2010YOUY01 perhaps this is related to the aggregate refactor

[alamb]

Update it is not clear to me that this is a regression or not. I am working on a reproducer to be sure

• Native collect_set(struct) aggregate crashes on spill emit datafusion-comet#5239 (comment)

[alamb]

I made a reproducer here:

• test: end-to-end reproducer for aggregating batches with stricter nested nullability than the declared schema #24278
  And it fails on both 54 and main (55) so I have determined it is not a regression