[GitHub] [arrow-datafusion] mustafasrepo commented on a diff in pull request #6592: Minor: Add additional docstrings to Window function implementations

["mustafasrepo (via GitHub)" <gi...@apache.org>]

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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