mustafasrepo commented on code in PR #6592:
URL: https://github.com/apache/arrow-datafusion/pull/6592#discussion_r1223906161
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datafusion/physical-expr/src/window/built_in_window_function_expr.rs:
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@@ -56,19 +62,36 @@ pub trait BuiltInWindowFunctionExpr: Send + Sync +
std::fmt::Debug {
.collect()
}
- /// Create built-in window evaluator with a batch
+ /// Create a [`PartitionEvaluator`] for evaluating the function on
+ /// a particular partition.
fn create_evaluator(&self) -> Result<Box<dyn PartitionEvaluator>>;
- /// Construct Reverse Expression that produces the same result
- /// on a reversed window. For example `lead(10)` --> `lag(10)`
+ /// Construct a new [`BuiltInWindowFunctionExpr`] that produces
+ /// the same result as this function on a window with reverse
+ /// order. The return value of this function is used by the
+ /// DataFusion optimizer to avoid resorting the data when
Review Comment:
Maybe we can use `re-sorting` instead of `resorting`.
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