DPL Analysis: add DefinesDelayed allowing to set the expressions in a process function, e.g. after calculating some required input values

Framework/Core/include/Framework/AnalysisHelpers.h

@@ -340,8 +340,9 @@ concept is_spawns = requires(T t) {
 /// The actual expressions have to be set in init() for the configurable expression
 /// columns, used to define the table
 
-template <is_dynamically_spawnable T>
+template <is_dynamically_spawnable T, bool DELAYED = false>
 struct Defines : decltype(transformBase<T>()) {
+  static constexpr bool delayed = DELAYED;
   using spawnable_t = T;
   using metadata = decltype(transformBase<T>())::metadata;
   using extension_t = typename metadata::extension_table_t;
@@ -373,13 +374,26 @@ struct Defines : decltype(transformBase<T>()) {
   std::array<o2::framework::expressions::Projector, N> projectors;
   std::shared_ptr<gandiva::Projector> projector = nullptr;
   std::shared_ptr<arrow::Schema> schema = std::make_shared<arrow::Schema>(o2::soa::createFieldsFromColumns(placeholders_pack_t{}));
+  std::shared_ptr<arrow::Schema> inputSchema = nullptr;
+
+  bool needRecompilation = false;
+
+  void recompile()
+  {
+    projector = framework::expressions::createProjectorHelper(N, projectors.data(), inputSchema, schema->fields());
+  }
 };
 
+template <is_dynamically_spawnable T>
+using DefinesDelayed = Defines<T, true>;
+
 template <typename T>
 concept is_defines = requires(T t) {
   typename T::metadata;
   requires std::same_as<decltype(t.pack()), typename T::placeholders_pack_t>;
   requires std::same_as<decltype(t.projector), std::shared_ptr<gandiva::Projector>>;
+  requires std::same_as<decltype(t.needRecompilation), bool>;
+  &T::recompile;
 };
 
 /// Policy to control index building

Framework/Core/include/Framework/AnalysisManagers.h

@@ -307,13 +307,50 @@ bool prepareOutput(ProcessingContext& context, T& builds)
 
 template <is_defines T>
 bool prepareOutput(ProcessingContext& context, T& defines)
+  requires(T::delayed == false)
 {
   using metadata = o2::aod::MetadataTrait<o2::aod::Hash<T::spawnable_t::ref.desc_hash>>::metadata;
   auto originalTable = soa::ArrowHelpers::joinTables(extractOriginals<metadata::sources.size(), metadata::sources>(context), std::span{metadata::base_table_t::originalLabels});
   if (originalTable->schema()->fields().empty() == true) {
     using base_table_t = typename T::base_table_t::table_t;
     originalTable = makeEmptyTable<base_table_t>(o2::aod::label<metadata::extension_table_t::ref>());
   }
+  if (defines.inputSchema == nullptr) {
+    defines.inputSchema = originalTable->schema();
+  }
+  using D = o2::aod::Hash<metadata::extension_table_t::ref.desc_hash>;
+
+  defines.extension = std::make_shared<typename T::extension_t>(o2::framework::spawner<D>(originalTable,
+                                                                                          o2::aod::label<metadata::extension_table_t::ref>(),
+                                                                                          defines.projectors.data(),
+                                                                                          defines.projector,
+                                                                                          defines.schema));
+  defines.table = std::make_shared<typename T::spawnable_t::table_t>(soa::ArrowHelpers::joinTables({defines.extension->asArrowTable(), originalTable}, std::span{T::spawnable_t::table_t::originalLabels}));
+  return true;
+}
+
+template <typename T>
+bool prepareDelayedOutput(ProcessingContext&, T&)
+{
+  return false;
+}
+
+template <is_defines T>
+  requires(T::delayed == true)
+bool prepareDelayedOutput(ProcessingContext& context, T& defines)
+{
+  if (defines.needRecompilation) {
+    defines.recompile();
+  }
+  using metadata = o2::aod::MetadataTrait<o2::aod::Hash<T::spawnable_t::ref.desc_hash>>::metadata;
+  auto originalTable = soa::ArrowHelpers::joinTables(extractOriginals<metadata::sources.size(), metadata::sources>(context), std::span{metadata::base_table_t::originalLabels});
+  if (originalTable->schema()->fields().empty() == true) {
+    using base_table_t = typename T::base_table_t::table_t;
+    originalTable = makeEmptyTable<base_table_t>(o2::aod::label<metadata::extension_table_t::ref>());
+  }
+  if (defines.inputSchema == nullptr) {
+    defines.inputSchema = originalTable->schema();
+  }
   using D = o2::aod::Hash<metadata::extension_table_t::ref.desc_hash>;
 
   defines.extension = std::make_shared<typename T::extension_t>(o2::framework::spawner<D>(originalTable,

Framework/Core/include/Framework/AnalysisTask.h

@@ -643,6 +643,8 @@ DataProcessorSpec adaptAnalysisTask(ConfigContext const& ctx, Args&&... args)
           return false;
         },
         *task.get());
+      // prepare delayed outputs
+      homogeneous_apply_refs([&pc](auto& element) { return analysis_task_parsers::prepareDelayedOutput(pc, element); }, *task.get());
       // finalize outputs
       homogeneous_apply_refs([&pc](auto& element) { return analysis_task_parsers::finalizeOutput(pc, element); }, *task.get());
     };

Framework/Core/test/test_Concepts.cxx

@@ -32,6 +32,15 @@ struct P {
   PROCESS_SWITCH(P, process1, "", true);
 };
 
+namespace o2::aod
+{
+namespace ct
+{
+DECLARE_SOA_CONFIGURABLE_EXPRESSION_COLUMN(Test, test, float, "test");
+}
+DECLARE_SOA_CONFIGURABLE_EXTENDED_TABLE(TracksMore, TracksIU, "TRKMORE", ct::Test);
+} // namespace o2::aod
+
 TEST_CASE("IdentificationConcepts")
 {
   // ASoA
@@ -122,6 +131,11 @@ TEST_CASE("IdentificationConcepts")
   Builds<o2::aod::Run3MatchedSparse> bld;
   REQUIRE(is_builds<decltype(bld)>);
 
+  Defines<o2::aod::TracksMore> def;
+  DefinesDelayed<o2::aod::TracksMore> ddef;
+  REQUIRE(is_defines<decltype(def)>);
+  REQUIRE(is_defines<decltype(ddef)>);
+
   OutputObj<TH1F> oo{"test"};
   REQUIRE(is_outputobj<decltype(oo)>);