feat: add datatype integration test for struct (#1102)

Fixes #1096

Author: devjgm

google/cloud/spanner/integration_tests/data_types_integration_test.cc

@@ -295,6 +295,49 @@ TEST_F(DataTypeIntegrationTest, WriteReadArrayDate) {
   EXPECT_THAT(*result, UnorderedElementsAreArray(data));
 }
 
+// This test differs a lot from the other tests since Spanner STRUCT types may
+// not be used as column types, and they may not be returned as top-level
+// objects in a select statement. See
+// https://cloud.google.com/spanner/docs/data-types#struct-type for more info.
+//
+// So the approach taken here instead is to use a STRUCT (i.e., a std::tuple<>
+// in the C++ world), as a bound SQL query parameter to insert some data into
+// the table. This, in a way, tests the "write" path.
+//
+// To test the "read" path, we create a query that returns an array of struct,
+// that we then compare to the original data.
+TEST_F(DataTypeIntegrationTest, InsertAndQueryWithStruct) {
+  using StructType =
+      std::tuple<std::pair<std::string, std::string>,
+                 std::pair<std::string, std::vector<std::int64_t>>>;
+  auto data = StructType{{"StringValue", "xx"}, {"ArrayInt64Value", {1, 2, 3}}};
+
+  auto& client = *client_;
+  auto commit_result = client.Commit(
+      [&data, &client](Transaction const& txn) -> StatusOr<Mutations> {
+        auto dml_result = client.ExecuteDml(
+            txn,
+            SqlStatement(
+                "INSERT INTO DataTypes (Id, StringValue, ArrayInt64Value)"
+                "VALUES(@id, @struct.StringValue, @struct.ArrayInt64Value)",
+                {{"id", Value("id-1")}, {"struct", Value(data)}}));
+        if (!dml_result) return dml_result.status();
+        return Mutations{};
+      });
+  ASSERT_STATUS_OK(commit_result);
+
+  auto rows = client_->ExecuteQuery(
+      SqlStatement("SELECT ARRAY(SELECT STRUCT(StringValue, ArrayInt64Value)) "
+                   "FROM DataTypes"));
+  using RowType = std::tuple<std::vector<StructType>>;
+  auto row = GetSingularRow(StreamOf<RowType>(rows));
+  ASSERT_STATUS_OK(row);
+
+  auto const& v = std::get<0>(*row);
+  EXPECT_EQ(1, v.size());
+  EXPECT_EQ(data, v[0]);
+}
+
 }  // namespace
 }  // namespace SPANNER_CLIENT_NS
 }  // namespace spanner