First look at the DuckDB C++ API

There is no vcpkg for it as yet, documentation seems a little sparse on
the C++ side.

Author: cryos

angohr/CMakeLists.txt

@@ -2,15 +2,19 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
 find_package(fmt CONFIG REQUIRED)
+find_package(DuckDB CONFIG REQUIRED)
+# This is just for DuckDB...their config file doesn't find Threads.
+find_package(Threads REQUIRED)
 
 add_library(core)
 target_sources(core
   PUBLIC
     FILE_SET CXX_MODULES FILES
       array.cpp
       core.cpp
+      database.cpp
       ello.cpp)
-target_link_libraries(core PRIVATE fmt::fmt)
+target_link_libraries(core PRIVATE fmt::fmt duckdb)
 add_library(angohr::core ALIAS core)
 
 add_executable(angohr angohr.cpp)

angohr/core.cpp

@@ -5,4 +5,6 @@ export module core;
 
 export import : iface.array;
 
+export import : iface.database;
+
 export import : iface.ello;

angohr/database.cpp

@@ -0,0 +1,66 @@
+// SPDX-FileCopyrightText: Copyright contributors to the Angohr project
+// SPDX-License-Identifier: BSD-3-Clause
+
+module;
+
+#include <duckdb.hpp>
+
+export module core : iface.database;
+
+namespace core {
+
+export class QueryResult
+{
+public:
+  QueryResult(std::unique_ptr<duckdb::MaterializedQueryResult> result) {
+    m_result = std::move(result);
+  }
+  int rowCount() {
+    if (m_result)
+      return m_result->RowCount();
+    return -1;
+  }
+  std::vector<std::string> names()
+  {
+    if (m_result)
+      return m_result->names;
+    return std::vector<std::string>();
+  }
+private:
+  std::unique_ptr<duckdb::MaterializedQueryResult> m_result;
+};
+
+export class Database
+{
+public:
+  Database();
+  ~Database() = default;
+  
+  QueryResult query(std::string query);
+  void print(std::string query);
+
+private:
+  std::unique_ptr<duckdb::DuckDB> m_database;
+  std::unique_ptr<duckdb::Connection> m_conn;
+};
+
+Database::Database()
+{
+  m_database = std::make_unique<duckdb::DuckDB>(nullptr);
+  m_conn = std::make_unique<duckdb::Connection>(*m_database);
+}
+
+QueryResult Database::query(std::string query)
+{
+  QueryResult result(m_conn->Query(query));
+  return result;
+
+}
+
+void Database::print(std::string query)
+{
+  auto result = m_conn->Query(query);
+  result->Print();
+}
+
+}

angohr/ello.cpp

@@ -3,7 +3,7 @@
 
 module;
 
-#include <algorithm>
+#include <algorithm> // Included to avoid a duplicate symbol error
 #include <fmt/core.h>
 #include <spdlog/spdlog.h>
 

tests/CMakeLists.txt

@@ -3,7 +3,7 @@
 
 find_package(GTest CONFIG REQUIRED)
 
-add_executable(angohr-test angohr-test.cpp)
+add_executable(angohr-test angohr-test.cpp database-test.cpp)
 target_link_libraries(angohr-test PRIVATE GTest::gtest GTest::gtest_main angohr::core)
 set_target_properties(angohr-test
   PROPERTIES

tests/database-test.cpp

@@ -0,0 +1,19 @@
+// SPDX-FileCopyrightText: Copyright contributors to the Angohr project
+// SPDX-License-Identifier: BSD-3-Clause
+
+import core;
+
+#include <gtest/gtest.h>
+
+TEST(Database, VerifyBasics) {
+  core::Database database;
+  database.query("CREATE TABLE integers (i INTEGER, j INTEGER)");
+  database.query("INSERT INTO integers VALUES (3, 4), (5, 6), (7, NULL)");
+  database.print("SELECT * FROM integers");
+  auto res = database.query("SELECT * FROM integers");
+  EXPECT_EQ(res.rowCount(), 3);
+  auto names = res.names();
+  EXPECT_EQ(names.size(), 2);
+  EXPECT_EQ(names[0], "i");
+  EXPECT_EQ(names[1], "j");
+}