2010YOUY01 commented on code in PR #16234:
URL: https://github.com/apache/datafusion/pull/16234#discussion_r2125366399
##########
datafusion/physical-expr/src/window/aggregate.rs:
##########
@@ -85,6 +88,25 @@ impl PlainAggregateWindowExpr {
);
}
}
+
+ // Returns true if every row in the partition has the same window frame.
This allows
+ // for preventing bound + function calculation for every row due to the
values being the
+ // same.
+ //
+ // This occurs when both bounds fall under either condition below:
+ // 1. Bound is unbounded (`Preceding` or `Following`)
+ // 2. Bound is `CurrentRow` while using `Range` units with no order by
clause
Review Comment:
```suggestion
// 2. Bound is `CurrentRow` while using `Range` units with no order by
clause
// This results in an invalid range specification. Following
PostgreSQL’s convention,
// we interpret this as the entire partition being used for the current
window frame.
```
##########
datafusion/physical-expr/src/window/window_expr.rs:
##########
@@ -186,6 +186,10 @@ pub trait AggregateWindowExpr: WindowExpr {
accumulator: &mut Box<dyn Accumulator>,
) -> Result<ScalarValue>;
+ /// Indicates whether this window function always produces the same result
+ /// for all rows in the partition.
+ fn is_constant(&self) -> bool;
Review Comment:
```suggestion
fn is_constant_in_partition(&self) -> bool;
```
nit: It would be great to be more specific.
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