comphead commented on code in PR #13637:
URL: https://github.com/apache/datafusion/pull/13637#discussion_r1870122310
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datafusion-examples/examples/advanced_udf.rs:
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@@ -191,6 +199,48 @@ impl ScalarUDFImpl for PowUdf {
}
}
+/// Evaluate `base ^ exp` *without* allocating a new array, if possible
+fn pow_in_place(base: f64, exp_array: ArrayRef) -> Result<ArrayRef> {
+ // Calling `unary` creates a new array for the results. Avoiding
+ // allocations is a common optimization in performance critical code.
+ // arrow-rs allows this optimization via the `unary_mut`
+ // and `binary_mut` kernels in certain cases
+ //
+ // These kernels can only be used if there are no other references to
+ // the arrays (exp_array has to be the last remaining reference).
+ let owned_array = exp_array
+ // as before we downcast to Float64Array
+ .as_primitive::<Float64Type>()
+ // non-obviously, clone (which increments ref counts, it
+ // doesn't clone the data) to get an typed own array
+ // so we drop the original exp_array (untyped) reference
Review Comment:
does it clone the reference?
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