Fix incorrect result of approx_percentile in window operations

velox/functions/prestosql/aggregates/ApproxPercentileAggregate.cpp

@@ -213,6 +213,7 @@ class ApproxPercentileAggregate : public exec::Aggregate {
               vector_size_t index) {
             digest.estimateQuantiles(percentiles, rawValues + elementsCount);
             result->setOffsetAndSize(index, elementsCount, percentiles.size());
+            result->setNull(index, false);
             elementsCount += percentiles.size();
           });
     } else {

velox/functions/prestosql/aggregates/tests/ApproxPercentileTest.cpp

@@ -20,10 +20,12 @@
 #include "velox/exec/tests/utils/AssertQueryBuilder.h"
 #include "velox/exec/tests/utils/PlanBuilder.h"
 #include "velox/functions/lib/aggregates/tests/utils/AggregationTestBase.h"
+#include "velox/functions/lib/window/tests/WindowTestBase.h"
 
 using namespace facebook::velox::exec;
 using namespace facebook::velox::exec::test;
 using namespace facebook::velox::functions::aggregate::test;
+using namespace facebook::velox::window::test;
 
 namespace facebook::velox::aggregate::test {
 
@@ -565,5 +567,32 @@ TEST_F(ApproxPercentileTest, nullPercentile) {
       "Percentile cannot be null");
 }
 
+class ApproxPercentileWindowTest : public WindowTestBase {
+ protected:
+  void SetUp() override {
+    WindowTestBase::SetUp();
+    random::setSeed(0);
+  }
+};
+
+TEST_F(ApproxPercentileWindowTest, window) {
+  auto data = makeRowVector(
+      {makeFlatVector<int32_t>({1, 2, 3}),
+       makeNullableFlatVector<int32_t>({10, std::nullopt, 30}),
+       makeArrayVectorFromJson<double>({"[0.5]", "[0.5]", "[0.5]"})});
+  auto expected = makeRowVector({
+      makeFlatVector<int32_t>({1, 2, 3}),
+      makeNullableFlatVector<int32_t>({10, std::nullopt, 30}),
+      makeArrayVectorFromJson<double>({"[0.5]", "[0.5]", "[0.5]"}),
+      makeNullableArrayVector<int32_t>({{{10}}, std::nullopt, {{30}}}),
+  });
+  testWindowFunction(
+      {data},
+      "approx_percentile(c1, c2)",
+      "order by c0",
+      "rows between current row and current row",
+      expected);
+}
+
 } // namespace
 } // namespace facebook::velox::aggregate::test