DPL Analysis: simple marker column template (#8783)

Author: aalkin

Framework/Core/include/Framework/ASoA.h

@@ -381,6 +381,36 @@ struct IndexColumn {
   static constexpr const char* const& columnLabel() { return INHERIT::mLabel; }
 };
 
+template <typename INHERIT>
+struct MarkerColumn {
+  using inherited_t = INHERIT;
+
+  using persistent = std::false_type;
+  static constexpr const char* const& columnLabel() { return INHERIT::mLabel; }
+};
+
+template <size_t M = 0>
+struct Marker : o2::soa::MarkerColumn<Marker<M>> {
+  using type = size_t;
+  using base = o2::soa::MarkerColumn<Marker<M>>;
+  constexpr inline static auto value = M;
+
+  Marker() = default;
+  Marker(Marker const&) = default;
+  Marker(Marker&&) = default;
+
+  Marker& operator=(Marker const&) = default;
+  Marker& operator=(Marker&&) = default;
+
+  Marker(arrow::ChunkedArray const*) {}
+  constexpr inline auto mark()
+  {
+    return value;
+  }
+
+  static constexpr const char* mLabel = "Marker";
+};
+
 template <int64_t START = 0, int64_t END = -1>
 struct Index : o2::soa::IndexColumn<Index<START, END>> {
   using base = o2::soa::IndexColumn<Index<START, END>>;

Framework/Core/test/test_ASoA.cxx

@@ -41,6 +41,10 @@ DECLARE_SOA_EXPRESSION_COLUMN(ESum, esum, int32_t, test ::x + test::y);
 DECLARE_SOA_TABLE(Points, "TST", "POINTS", test::X, test::Y);
 DECLARE_SOA_TABLE(Points3Ds, "TST", "PTS3D", o2::soa::Index<>, test::X, test::Y, test::Z);
 
+DECLARE_SOA_TABLE(Points3DsMk1, "TST", "PTS3D_1", o2::soa::Index<>, o2::soa::Marker<1>, test::X, test::Y, test::Z);
+DECLARE_SOA_TABLE(Points3DsMk2, "TST", "PTS3D_2", o2::soa::Index<>, o2::soa::Marker<2>, test::X, test::Y, test::Z);
+DECLARE_SOA_TABLE(Points3DsMk3, "TST", "PTS3D_3", o2::soa::Index<>, o2::soa::Marker<3>, test::X, test::Y, test::Z);
+
 namespace test
 {
 DECLARE_SOA_COLUMN_FULL(SomeBool, someBool, bool, "someBool");
@@ -69,6 +73,24 @@ DECLARE_SOA_COLUMN(L2, l2, std::vector<int>);
 
 DECLARE_SOA_TABLE(Lists, "TST", "LISTS", o2::soa::Index<>, test::L1, test::L2);
 
+BOOST_AUTO_TEST_CASE(TestMarkers)
+{
+  TableBuilder b1;
+  auto pwriter = b1.cursor<Points3Ds>();
+  for (auto i = 0; i < 20; ++i) {
+    pwriter(0, -1 * i, (int)(i / 2), 2 * i);
+  }
+  auto t1 = b1.finalize();
+
+  auto pt = Points3Ds{t1};
+  auto pt1 = Points3DsMk1{t1};
+  auto pt2 = Points3DsMk2{t1};
+  auto pt3 = Points3DsMk3{t1};
+  BOOST_REQUIRE_EQUAL(pt1.begin().mark(), (size_t)1);
+  BOOST_REQUIRE_EQUAL(pt2.begin().mark(), (size_t)2);
+  BOOST_REQUIRE_EQUAL(pt3.begin().mark(), (size_t)3);
+}
+
 BOOST_AUTO_TEST_CASE(TestTableIteration)
 {
   TableBuilder builder;