Fokko commented on code in PR #4727:
URL: https://github.com/apache/iceberg/pull/4727#discussion_r867736811
##########
python/src/iceberg/transforms.py:
##########
@@ -249,6 +249,32 @@ def result_type(self, source: IcebergType) -> IcebergType:
return StringType()
+class VoidTransform(Transform):
+ """A transform that always returns None"""
+
+ _instance = None
+
+ def __new__(cls):
+ if cls._instance is None:
+ cls._instance = super(VoidTransform, cls).__new__(cls)
+ return cls._instance
+
+ def __init__(self):
+ super().__init__("void", "transforms.always_null()")
+
+ def apply(self, value):
Review Comment:
Related to https://github.com/apache/iceberg/pull/4728/
```suggestion
def apply(self, value: Optional[S]) -> Optional[int]:
```
##########
python/src/iceberg/transforms.py:
##########
@@ -249,6 +249,32 @@ def result_type(self, source: IcebergType) -> IcebergType:
return StringType()
+class VoidTransform(Transform):
+ """A transform that always returns None"""
+
+ _instance = None
+
+ def __new__(cls):
Review Comment:
We could add a test for this:
```python
def test_check_if_identical():
assert transforms.always_null() is transforms.always_null()
```
##########
python/src/iceberg/transforms.py:
##########
@@ -249,6 +249,32 @@ def result_type(self, source: IcebergType) -> IcebergType:
return StringType()
+class VoidTransform(Transform):
+ """A transform that always returns None"""
+
+ _instance = None
+
+ def __new__(cls):
+ if cls._instance is None:
+ cls._instance = super(VoidTransform, cls).__new__(cls)
+ return cls._instance
+
+ def __init__(self):
+ super().__init__("void", "transforms.always_null()")
+
+ def apply(self, value):
+ return None
+
+ def can_transform(self, target: IcebergType) -> bool:
+ return True
+
+ def result_type(self, source: IcebergType) -> IcebergType:
+ return source
+
+ def to_human_string(self, value) -> str:
Review Comment:
```suggestion
def to_human_string(self, Optional[value]) -> str:
```
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