rdblue commented on code in PR #5030:
URL: https://github.com/apache/iceberg/pull/5030#discussion_r907878054
##########
python/src/iceberg/transforms.py:
##########
@@ -301,6 +301,91 @@ def _(self, value_type: IcebergType, value: int) -> str:
return datetime.to_human_timestamptz(value)
+class TruncateTransform(Transform[S, S]):
+ """A transform for truncating a value to a specified width.
+ Args:
+ source_type (IcebergType): An Iceberg Type of IntegerType, LongType,
StringType, BinaryType or DecimalType
+ width (int): The truncate width
+ Raises:
+ ValueError: If a type is provided that is incompatible with a Truncate
transform
+ """
+
+ def __init__(self, source_type: IcebergType, width: int):
+ super().__init__(
+ f"truncate[{width}]",
+ f"transforms.truncate(source_type={repr(source_type)},
width={width})",
+ )
+ self._type = source_type
+ self._width = width
+
+ @property
+ def width(self) -> int:
+ return self._width
+
+ @property
+ def type(self) -> IcebergType:
+ return self._type
+
+ def apply(self, value: Optional[S]) -> Optional[S]:
+ return self._truncate_value(value) if value is not None else None
+
+ @singledispatchmethod
+ def _truncate_value(self, value: S) -> S:
+ raise ValueError(f"Cannot truncate value: {value}")
+
+ @_truncate_value.register(int)
+ def _(self, value):
+ """Truncate a given int value into a given width if feasible."""
+ if type(self._type) in {IntegerType, LongType}:
+ return value - value % self._width
+ else:
+ raise ValueError(f"Cannot truncate type: {self._type} for value:
{value}")
+
+ @_truncate_value.register(str)
+ def _(self, value):
+ """Truncate a given string to a given width."""
+ return value[0 : min(self._width, len(value))]
Review Comment:
This appears correct to me:
```python
truncate("abc\u2603de") # => "abc\u2603d"
```
We should make sure this or another multi-byte character test is in the
tests.
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