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[Data] Add descriptive error if user tries to download from invalid column #56852

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Merged
bveeramani merged 1 commit into from
Sep 24, 2025
Merged

[Data] Add descriptive error if user tries to download from invalid column #56852

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7 changes: 7 additions & 0 deletions python/ray/data/_internal/planner/plan_download_op.py
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Original file line number Diff line number Diff line change
Expand Up @@ -244,6 +244,13 @@ def get_file_size(uri_path, fs):
return file_sizes

def __call__(self, block: pa.Table) -> Iterator[pa.Table]:
if self._uri_column_name not in block.column_names:
raise ValueError(
"Ray Data tried to download URIs from a column named "
f"{self._uri_column_name!r}, but a column with that name doesn't "
"exist. Is the specified download column correct?"
)
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@cursor cursor bot Sep 23, 2025

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Bug: Column Check Fails on Non-PyArrow Tables

The column existence check accesses block.column_names before the block is guaranteed to be a PyArrow table. If the input isn't a PyArrow table (e.g., a pandas DataFrame), this can raise an AttributeError or lead to incorrect results.

Fix in Cursor Fix in Web


if not isinstance(block, pa.Table):
block = BlockAccessor.for_block(block).to_arrow()

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2 changes: 1 addition & 1 deletion python/ray/data/tests/test_download_expression.py
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Expand Up @@ -221,7 +221,7 @@ def test_download_expression_invalid_uri_column(self):
ds_with_downloads = ds.with_column("bytes", download("non_existent_column"))

# Should raise error when trying to execute
with pytest.raises(Exception): # Could be KeyError or similar
with pytest.raises(ValueError):
ds_with_downloads.take_all()

def test_download_expression_with_null_uris(self):
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