Add skewness Spark agg function

velox/exec/tests/SparkAggregationFuzzerTest.cpp

@@ -70,7 +70,13 @@ int main(int argc, char** argv) {
       {"avg_partial", ""},
       {"avg_merge", ""},
       {"max_by", ""},
-      {"min_by", ""}};
+      {"min_by", ""},
+      // The skewness functions of Velox and DuckDB use different
+      // algorithms.
+      // https://github.com/facebookincubator/velox/issues/4845
+      {"skewness", ""},
+      {"skewness_partial", ""},
+      {"skewness_merge", ""}};
 
   size_t initialSeed = FLAGS_seed == 0 ? std::time(nullptr) : FLAGS_seed;
   auto duckQueryRunner =

velox/functions/lib/aggregates/CMakeLists.txt

@@ -12,8 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-add_library(velox_functions_aggregates SingleValueAccumulator.cpp
-                                       AverageAggregateBase.cpp ValueSet.cpp)
+add_library(
+  velox_functions_aggregates
+  AverageAggregateBase.cpp CentralMomentsAggregatesBase.cpp
+  SingleValueAccumulator.cpp ValueSet.cpp)
 
 target_link_libraries(velox_functions_aggregates velox_exec
                       velox_presto_serializer Folly::folly)

velox/functions/lib/aggregates/CentralMomentsAggregatesBase.cpp

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "velox/functions/lib/aggregates/CentralMomentsAggregatesBase.h"
+
+namespace facebook::velox::functions::aggregate {
+
+void checkAccumulatorRowType(
+    const TypePtr& type,
+    const std::string& errorMessage) {
+  VELOX_CHECK_EQ(type->kind(), TypeKind::ROW, "{}", errorMessage);
+  VELOX_CHECK_EQ(
+      type->childAt(kCentralMomentsIndices.count)->kind(),
+      TypeKind::BIGINT,
+      "{}",
+      errorMessage);
+  VELOX_CHECK_EQ(
+      type->childAt(kCentralMomentsIndices.m1)->kind(),
+      TypeKind::DOUBLE,
+      "{}",
+      errorMessage);
+  VELOX_CHECK_EQ(
+      type->childAt(kCentralMomentsIndices.m2)->kind(),
+      TypeKind::DOUBLE,
+      "{}",
+      errorMessage);
+  VELOX_CHECK_EQ(
+      type->childAt(kCentralMomentsIndices.m3)->kind(),
+      TypeKind::DOUBLE,
+      "{}",
+      errorMessage);
+  VELOX_CHECK_EQ(
+      type->childAt(kCentralMomentsIndices.m4)->kind(),
+      TypeKind::DOUBLE,
+      "{}",
+      errorMessage);
+}
+
+} // namespace facebook::velox::functions::aggregate