Re: [PR] [GLUTEN-13273][VL] Keep struct field names in udfLibraryPaths UDF signatures [gluten]

["Copilot (via GitHub)" <gi...@apache.org>]

Copilot commented on code in PR #13274:
URL: https://github.com/apache/gluten/pull/13274#discussion_r4273355414


##########
cpp/velox/udf/examples/MyUDF.cc:
##########
@@ -108,6 +109,84 @@ class MyUdfPlusOneRegisterer final : public gluten::UdfRegisterer {
 
 } // namespace myudfplusone
 
+namespace myudfsumrow {
+
+template <typename T>
+struct MyUdfSumRowFunction {
+  VELOX_DEFINE_FUNCTION_TYPES(T);
+
+  FOLLY_ALWAYS_INLINE bool call(int64_t& result, const arg_type<Row<int64_t, int64_t>>& row) {
+    const auto a = row.template at<0>();
+    const auto b = row.template at<1>();
+    if (!a.has_value() || !b.has_value()) {
+      return false;
+    }
+    result = a.value() + b.value();
+    return true;
+  }

Review Comment:
   The UDF dereferences the struct argument unconditionally. If the *struct itself* is null (e.g., `CAST(NULL AS STRUCT<a:bigint,b:bigint>)`), accessing `row.at<0>()`/`row.at<1>()` can be invalid. Fix by explicitly handling a null struct argument (e.g., check `row.has_value()` / nullability per Velox UDF conventions) before reading fields, and return `false` to produce a null result when the input row is null.



##########
cpp/velox/udf/examples/MyUDF.cc:
##########
@@ -108,6 +109,84 @@ class MyUdfPlusOneRegisterer final : public gluten::UdfRegisterer {
 
 } // namespace myudfplusone
 
+namespace myudfsumrow {
+
+template <typename T>
+struct MyUdfSumRowFunction {
+  VELOX_DEFINE_FUNCTION_TYPES(T);
+
+  FOLLY_ALWAYS_INLINE bool call(int64_t& result, const arg_type<Row<int64_t, int64_t>>& row) {
+    const auto a = row.template at<0>();
+    const auto b = row.template at<1>();
+    if (!a.has_value() || !b.has_value()) {
+      return false;
+    }
+    result = a.value() + b.value();
+    return true;
+  }
+};
+
+// name: myudf_sum_row
+// signatures:
+//    struct<a:bigint,b:bigint> -> bigint
+// type: SimpleFunction
+class MyUdfSumRowRegisterer final : public gluten::UdfRegisterer {
+ public:
+  int getNumUdf() override {
+    return 1;
+  }
+
+  void populateUdfEntries(int& index, gluten::UdfEntry* udfEntries) override {
+    udfEntries[index++] = {name_.c_str(), kBigInt, 1, arg_, false, false};
+  }
+
+  void registerSignatures() override {
+    facebook::velox::registerFunction<MyUdfSumRowFunction, int64_t, Row<int64_t, int64_t>>({name_});
+  }
+
+ private:
+  const std::string name_ = "myudf_sum_row";
+  const char* arg_[1] = {kStructAB};
+};
+
+} // namespace myudfsumrow
+
+namespace myudfmakerow {
+
+template <typename T>
+struct MyUdfMakeRowFunction {
+  VELOX_DEFINE_FUNCTION_TYPES(T);
+
+  FOLLY_ALWAYS_INLINE void call(out_type<Row<int64_t, int64_t>>& result, const int64_t& a) {
+    result = std::make_tuple(a, a + 1);

Review Comment:
   This example UDF takes `a` as non-nullable (`const int64_t&`). In Spark SQL, `BIGINT` inputs are generally nullable, so passing null could lead to incorrect behavior or crashes depending on how the binding is performed. Consider using Velox's nullable argument type (`arg_type<int64_t>`) and emitting a null result when `a` is null, or otherwise documenting/enforcing non-nullability in the signature/registration.



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