fix: preserve precision for large integral string conversions

Author: fallintoplace

pyiceberg/conversions.py

@@ -143,7 +143,7 @@ def _(primitive_type: PrimitiveType, value_str: str) -> int:
     _, _, exponent = Decimal(value_str).as_tuple()
     if exponent != 0:  # Raise if there are digits to the right of the decimal
         raise ValueError(f"Cannot convert partition value, value cannot have fractional digits for {primitive_type} partition")
-    return int(float(value_str))
+    return int(value_str)
 
 
 @partition_to_py.register(FloatType)

pyiceberg/expressions/literals.py

@@ -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_DOWN, ROUND_HALF_UP, Decimal
 from functools import singledispatchmethod
 from math import isnan
 from typing import Any, Generic
@@ -555,27 +555,27 @@ def _(self, _: StringType) -> Literal[str]:
     @to.register(IntegerType)
     def _(self, type_var: IntegerType) -> Literal[int]:
         try:
-            number = int(float(self.value))
+            number = int(Decimal(self.value).to_integral_value(rounding=ROUND_DOWN))
 
             if IntegerType.max < number:
                 return IntAboveMax()
             elif IntegerType.min > number:
                 return IntBelowMin()
             return LongLiteral(number)
-        except ValueError as e:
+        except (ArithmeticError, OverflowError, ValueError) as e:
             raise ValueError(f"Could not convert {self.value} into a {type_var}") from e
 
     @to.register(LongType)
     def _(self, type_var: LongType) -> Literal[int]:
         try:
-            long_value = int(float(self.value))
+            long_value = int(Decimal(self.value).to_integral_value(rounding=ROUND_DOWN))
             if LongType.max < long_value:
                 return LongAboveMax()
             elif LongType.min > long_value:
                 return LongBelowMin()
             else:
                 return LongLiteral(long_value)
-        except (TypeError, ValueError) as e:
+        except (ArithmeticError, OverflowError, TypeError, ValueError) as e:
             raise ValueError(f"Could not convert {self.value} into a {type_var}") from e
 
     @to.register(DateType)

tests/expressions/test_literals.py

@@ -845,6 +845,14 @@ def test_string_to_int_min_value() -> None:
     assert isinstance(literal(str(IntegerType.min - 1)).to(IntegerType()), IntBelowMin)
 
 
+def test_string_to_long_max_value_without_precision_loss() -> None:
+    assert literal(str(LongType.max)).to(LongType()) == literal(LongType.max)
+
+
+def test_string_to_long_large_integer_without_precision_loss() -> None:
+    assert literal("9007199254740993").to(LongType()) == literal(9007199254740993)
+
+
 def test_string_to_integer_type_invalid_value() -> None:
     with pytest.raises(ValueError) as e:
         _ = literal("abc").to(IntegerType())

tests/test_conversions.py

@@ -160,8 +160,11 @@ def test_unscaled_to_decimal(unscaled: int, scale: int, expected_result: Decimal
         (IntegerType(), "1", 1),
         (IntegerType(), "9999", 9999),
         (LongType(), "123456789", 123456789),
+        (LongType(), "9007199254740993", 9007199254740993),
+        (LongType(), str(LongType.max), LongType.max),
         (FloatType(), "1.1", 1.1),
         (DoubleType(), "99999.9", 99999.9),
+        (TimestampNanoType(), "9007199254740993", 9007199254740993),
         (DecimalType(5, 2), "123.45", Decimal("123.45")),
         (StringType(), "foo", "foo"),
         (UUIDType(), "f79c3e09-677c-4bbd-a479-3f349cb785e7", uuid.UUID("f79c3e09-677c-4bbd-a479-3f349cb785e7")),