fix(decimal): use minimal byte length for negative powers of two - #3746
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kevinjqliu merged 3 commits intoAug 20, 2026
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LGTM thanks for catching and fixing this.
i pushed up a commit to rephrase some of the comments
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Thanks for the pr @vishnuprakaz |
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Reopening #3523, which was auto-closed for inactivity. Rebased on latest
main; the bug is still present.Closes #3522
Rationale for this change
bytes_requiredshould return the minimum number of bytes for a value, but it returns one byte too many for negatives like -128 and -32768.This matters because the decimal bucket transform hashes those bytes. The extra byte changes the hash, so PyIceberg can put a value in a different bucket than Spark/Java. For example,
Decimal("-1.28")goes to bucket 12 in PyIceberg but bucket 13 everywhere else.The fix computes the length from
(value + 1)for negative values, which gives the true minimum and matches the Iceberg spec.Are these changes tested?
Yes. Added tests for the -128 / -32768 / -8388608 boundary cases (where the old code was wrong) plus positive/negative controls. Lint and the decimal/conversion/transform tests pass.
Are there any user-facing changes?
Yes. For decimal values like -1.28, the computed bucket changes (e.g. 12 → 13) so it now matches other Iceberg engines.