Jefffrey commented on code in PR #19642:
URL: https://github.com/apache/datafusion/pull/19642#discussion_r2663351648
##########
datafusion/expr/src/udwf.rs:
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@@ -427,21 +440,130 @@ pub trait WindowUDFImpl: Debug + DynEq + DynHash + Send
+ Sync {
None
}
- /// If not causal, returns the effect this function will have on the window
+ /// Returns the effect this function has on limit pushdowns. See
[`LimitEffect`]
+ /// for more details.
+ ///
+ /// Defaults to [`LimitEffect::Unknown`].
fn limit_effect(&self, _args: &[Arc<dyn PhysicalExpr>]) -> LimitEffect {
LimitEffect::Unknown
}
}
-/// the effect this function will have on the limit pushdown
+/// The effect this function will have on limit pushdowns through a window
bound.
Review Comment:
So does that mean we're planning to alter/remove this `limit_effect()` API,
even though it was recently introduced?
I agree with this being too overly specific, but considering we introduced a
new API to `WindowUDFImpl` just for this optimizer rule I felt it would help
users understand why this API exists and how it affects things in DataFusion.
As the documentation currently is on main, I find it hard to understand its
purpose so I assume it may be the same for other users. And the best way I
found to understand this was via an example usage (and so far the only usage).
Do you have a suggestion on how we could generalize this documentation in a
way that still helps users understand what it is for?
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