From 06fc222598d0cb9a0977170bcbcc077d59a854e2 Mon Sep 17 00:00:00 2001
From: Lawrence Mitchell <lmitchell@nvidia.com>
Date: Tue, 1 Oct 2024 10:01:08 +0000
Subject: [PATCH] Opt in, rather than opt out

---
 cpp/src/reductions/compound.cuh | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/cpp/src/reductions/compound.cuh b/cpp/src/reductions/compound.cuh
index b46d8edc872..cd9fade164a 100644
--- a/cpp/src/reductions/compound.cuh
+++ b/cpp/src/reductions/compound.cuh
@@ -18,6 +18,7 @@
 
 #include <cudf/dictionary/detail/iterator.cuh>
 #include <cudf/reduction/detail/reduction.cuh>
+#include <cudf/reduction/detail/reduction_operators.cuh>
 #include <cudf/scalar/scalar_factories.hpp>
 #include <cudf/utilities/error.hpp>
 #include <cudf/utilities/memory_resource.hpp>
@@ -59,9 +60,9 @@ std::unique_ptr<scalar> compound_reduction(column_view const& col,
 
   // All null input produces all null output
   if (valid_count == 0 ||
-      // Don't care about ddof argument of mean. For variance and
-      // standard deviation must have more valid entries than ddof.
-      !std::is_same_v<Op, cudf::reduction::detail::op::mean> && valid_count <= ddof) {
+      // Only care about ddof for standard deviation and variance right now
+      valid_count <= ddof && (std::is_same_v<Op, cudf::reduction::detail::op::standard_deviation> ||
+                              std::is_same_v<Op, cudf::reduction::detail::op::variance>)) {
     auto result = cudf::make_fixed_width_scalar(output_dtype, stream, mr);
     result->set_valid_async(false, stream);
     return result;