AP24110011695 opened a new issue, #4284:
URL: https://github.com/apache/iceberg-python/issues/4284
### Apache Iceberg version
main (0.12.0)
### Please describe the bug this is related to
Three decimal helpers still read a `Decimal`'s scale as
`abs(int(value.as_tuple().exponent))`. A Python `Decimal` carries the
**negated** scale as its exponent, so a value with a non-negative exponent —
e.g. `Decimal("1E+2")` (100 with scale −2) — is misread as having a positive
scale of 2. This is the same root cause as #3997, which fixed three call sites;
these remaining ones were not covered:
- `DecimalLiteral.increment()` — `pyiceberg/expressions/literals.py`
- `DecimalLiteral.decrement()` — `pyiceberg/expressions/literals.py`
- `truncate_decimal()` — `pyiceberg/utils/decimal.py`
### Describe how to reproduce the bug
```python
from decimal import Decimal
from pyiceberg.expressions.literals import DecimalLiteral
from pyiceberg.utils.decimal import truncate_decimal
DecimalLiteral(Decimal("1E+2")).increment().value # Decimal('0.02') —
expected 2E+2 (i.e. 200)
DecimalLiteral(Decimal("1E+2")).decrement().value # Decimal('0.00') —
expected 0E+2 (i.e. 0)
truncate_decimal(Decimal("1.5E+3"), 4) # Decimal('0.12') —
expected 1.2E+3 (i.e. 1200)
```
`increment()`/`decrement()` are used by the range-projection helpers in
`pyiceberg/transforms.py`, so any future path that hands them a negative-scale
`Decimal` produces bounds on the wrong order of magnitude. Schema-typed paths
currently reject such decimals at bind time (fixed by #3997 in
`to(DecimalType)`), which is why this went unnoticed — but the helpers
themselves still return corrupted values for valid `Decimal` input.
### Willingness to contribute
- [x] Yes. I will be willing to submit a PR for this bug.
---
_Transparent disclosure: this issue was investigated and filed with AI
assistance (reproduction verified locally on main @ e3564a5)._
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