Michael-J-Ward commented on code in PR #880:
URL: https://github.com/apache/datafusion-python/pull/880#discussion_r1777685386
##########
python/datafusion/udf.py:
##########
@@ -246,3 +246,229 @@ def udaf(
state_type=state_type,
volatility=volatility,
)
+
+
+class WindowEvaluator(metaclass=ABCMeta):
+ """Evaluator class for user defined window functions (UDWF).
+
+ It is up to the user to decide which evaluate function is appropriate.
+
+
|``uses_window_frame``|``supports_bounded_execution``|``include_rank``|function_to_implement|
+ |---|---|----|----|
+ |False (default) |False (default) |False (default) |
``evaluate_all`` |
+ |False |True |False |
``evaluate`` |
+ |False |True/False |True |
``evaluate_all_with_rank`` |
+ |True |True/False |True/False |
``evaluate`` |
+ """ # noqa: W505
+
+ def memoize(self) -> None:
+ """Perform a memoize operation to improve performance.
+
+ When the window frame has a fixed beginning (e.g UNBOUNDED
Review Comment:
Q for my own understanding:
Should this be "When the window frame has a fixed **bound** (beginning or
end)..."?
I ask because the docs use `last_value` as an example, and I don't see how
`last_value` could benefit from `memoize` because of a fixed **beginning**.
(If I'm correct, I'll go fix the docs upstream)
https://docs.rs/datafusion/latest/datafusion/logical_expr/trait.PartitionEvaluator.html#method.memoize
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