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fix: preserve list types for empty Parquet splits - #1040
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Use Arrow's record batch reader for empty splits so schema alignment preserves configured and stored list types. Add regression tests for empty-split schema consistency and end-of-stream behavior.
wgtmac
approved these changes
Oct 19, 2026
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Summary
When a split selects no row groups,
EmptyRecordBatchReader::schema()returnsnullptr, causing output schema alignment to be skipped. Empty splits can then reportlistinstead oflarge_list, ignoring the reader configuration or list types stored inARROW:schema.Remove
EmptyRecordBatchReaderand useGetRecordBatchReaderfor both empty and non-empty splits. This preserves schema consistency while still returning end-of-stream immediately for empty splits.Test plan
use-large-listenabled and disabled, stored list types, missing fields, nested field pruning and renaming, and projections without physical columns. Verify that empty-split schemas match the unsplit reader and the firstNext()returns end-of-stream.