fix: Avoid incorrect min/max stats for BYTE_ARRAY decimals of unequal byte lengths - #10861
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`compare_greater_byte_array_decimals` sign-extends the shorter value when comparing two's-complement byte arrays of different lengths. When the longer value's extra leading bytes were all sign-extension bytes, the final comparison dropped exactly one byte from each side and then lexicographically compares the remaining byte slices. This is incorrect when the byte slices are of different lengths. This can result in exact row-group/page stats with incorrect values (e.g., swapped min and max). Align the tails by skipping the length difference on the longer side only, matching parquet-mr. Closes apache#10860.
Jefffrey
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Aug 27, 2026
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FYI @etseidl |
etseidl
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I find this dizzying 😅. Thanks @neilconway!
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Which issue does this PR close?
BYTE_ARRAYDECIMALcolumns #10860.Rationale for this change
compare_greater_byte_array_decimalssign-extends the shorter value when comparing two's-complement byte arrays of different lengths. When the longer value's extra leading bytes were all sign-extension bytes, the final comparison dropped exactly one byte from each side and then lexicographically compares the remaining byte slices. This is incorrect when the byte slices are of different lengths.This can result in exact row-group/page stats with incorrect values (e.g., swapped min and max).
Align the tails by skipping the length difference on the longer side only, matching parquet-mr.
What changes are included in this PR?
Are these changes tested?
Yes; new tests added.
Are there any user-facing changes?
No.
AI usage
Bug found and fix written with Claude Code Fable 5; I reviewed and understand the resulting code.