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Convert float literals to wide decimal columns without InvalidOperation #4372

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Convert float literals to wide decimal columns without InvalidOperation #4372

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19 changes: 12 additions & 7 deletions pyiceberg/expressions/literals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@
import struct
from abc import ABC, abstractmethod
from datetime import date, datetime, time
from decimal import ROUND_HALF_UP, Decimal
from decimal import ROUND_HALF_UP, Decimal, getcontext, localcontext
from functools import singledispatchmethod
from math import isfinite, isnan
from typing import Any, Generic
Expand Down Expand Up @@ -371,6 +371,15 @@ def _(self, type_var: DecimalType) -> Literal[Decimal]:
return DecimalLiteral(Decimal((sign, digits + zeros, -type_var.scale)))


def _float_to_decimal(value: float, type_var: DecimalType) -> Decimal:
if not isfinite(value):
raise ValueError(f"Could not convert {value} into a {type_var}, value is not finite")
exact = Decimal(value)
# Quantize needs a context precision that covers every digit of the result, which can exceed the default 28 digits
with localcontext(prec=max(getcontext().prec, exact.adjusted() + type_var.scale + 2)):
return exact.quantize(Decimal((0, (1,), -type_var.scale)), rounding=ROUND_HALF_UP)


class FloatLiteral(Literal[float]):
def __init__(self, value: float) -> None:
super().__init__(value, float)
Expand Down Expand Up @@ -414,9 +423,7 @@ def _(self, _: DoubleType) -> Literal[float]:

@to.register(DecimalType)
def _(self, type_var: DecimalType) -> Literal[Decimal]:
if not isfinite(self.value):
raise ValueError(f"Could not convert {self.value} into a {type_var}, value is not finite")
return DecimalLiteral(Decimal(self.value).quantize(Decimal((0, (1,), -type_var.scale)), rounding=ROUND_HALF_UP))
return DecimalLiteral(_float_to_decimal(self.value, type_var))


class DoubleLiteral(Literal[float]):
Expand All @@ -441,9 +448,7 @@ def _(self, _: FloatType) -> Literal[float]:

@to.register(DecimalType)
def _(self, type_var: DecimalType) -> Literal[Decimal]:
if not isfinite(self.value):
raise ValueError(f"Could not convert {self.value} into a {type_var}, value is not finite")
return DecimalLiteral(Decimal(self.value).quantize(Decimal((0, (1,), -type_var.scale)), rounding=ROUND_HALF_UP))
return DecimalLiteral(_float_to_decimal(self.value, type_var))


class DateLiteral(Literal[int]):
Expand Down
10 changes: 10 additions & 0 deletions tests/expressions/test_literals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -293,6 +293,16 @@ def test_double_to_decimal_conversion_with_infinity() -> None:
assert "Could not convert inf into a decimal(9, 2), value is not finite" in str(e.value)


def test_float_to_decimal_conversion_beyond_default_context_precision() -> None:
# The default decimal context keeps 28 digits, fewer than a decimal(38, s) value can have
for value, decimal_type, expected in [
(2.0**87, DecimalType(38, 2), "154742504910672534362390528.00"),
(0.5, DecimalType(38, 30), "0.500000000000000000000000000000"),
]:
for lit in (FloatLiteral(value), DoubleLiteral(value)):
assert lit.to(decimal_type).value.as_tuple() == Decimal(expected).as_tuple(), (lit, decimal_type)


def test_decimal_to_decimal_conversion() -> None:
lit = literal(Decimal("34.11").quantize(Decimal(".01")))

Expand Down
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