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Preserve null lists when projecting a list of structs - #4129
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krishan711 wants to merge 2 commits into
Open
krishan711 wants to merge 2 commits into
krishan711 wants to merge 2 commits into
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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Rationale for this change
ArrowProjectionVisitor.listrebuilds a list of structs withLargeListArray.from_arrays(list_array.offsets, value_array). That drops the validity mask, so a null list is written as an empty list. This is the list version of #4118, which fixed the same thing for maps.The fix passes
mask=list_array.is_null().Are these changes tested?
Yes.
test__to_requested_schema_null_list_of_structscovers a full batch and a sliced one. It fails without the fix.test_null_list_and_mapasserted[[], [{"test": 1}]]forcol_list_with_struct, with a comment that it should be[None, [{"test": 1}]]once an Arrow issue was fixed. The null was lost by the rebuild here, not by Arrow:from_arrayswas given the offsets but not the validity, and a null list and an empty one share offsets. So the test now asserts[None, [{"test": 1}]].Are there any user-facing changes?
Null lists of structs stay null on write instead of becoming
[].