fix: emit empty RecordBatch for empty file writes #19370
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kosiew
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Dec 22, 2025
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| // if there is no batch send but with a single file, send an empty batch | ||
| if single_file_output && !is_batch_received { |
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The DataFrameWriteOptions::with_single_file_output() method should also be updated about empty DataFrame behavior.
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Done. Updated the doc comment for with_single_file_output()
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Dec 25, 2025
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LGTM
with some minor comments.
| df.write_csv(&path, crate::dataframe::DataFrameWriteOptions::new(), None) | ||
| .await?; | ||
| // Expected the file to exist | ||
| assert!(std::path::Path::new(&path).exists()); |
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Curious why there is no assertion of 0 lines here like you did for arrow, parquet files?
| df.write_json(&path, crate::dataframe::DataFrameWriteOptions::new(), None) | ||
| .await?; | ||
| // Expected the file to exist | ||
| assert!(std::path::Path::new(&path).exists()); |
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Curious why there is no assertion of 0 lines here like you did for arrow, parquet files?
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Which issue does this PR close?
Rationale for this change
If the input stream yields no RecordBatch at all, nothing gets sent downstream, and the writer never has a chance to produce a valid file. I added a small fallback: when single_file_output is enabled and no batches were received, we send a single empty RecordBatch with the input schema.
Are these changes tested?
Yes.
Are there any user-facing changes?