RInterface.hxx

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// Author: Enrico Guiraud, Danilo Piparo CERN  03/2017

/*************************************************************************
 * Copyright (C) 1995-2018, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#ifndef ROOT_RDF_TINTERFACE
#define ROOT_RDF_TINTERFACE

#include "ROOT/RDataSource.hxx"
#include "ROOT/RDF/ActionHelpers.hxx"
#include "ROOT/RDF/RBookedCustomColumns.hxx"
#include "ROOT/RDF/HistoModels.hxx"
#include "ROOT/RDF/InterfaceUtils.hxx"
#include "ROOT/RDF/RRange.hxx"
#include "ROOT/RDF/Utils.hxx"
#include "ROOT/RIntegerSequence.hxx"
#include "ROOT/RDF/RLazyDSImpl.hxx"
#include "ROOT/RResultPtr.hxx"
#include "ROOT/RSnapshotOptions.hxx"
#include "ROOT/RStringView.hxx"
#include "ROOT/TypeTraits.hxx"
#include "RtypesCore.h" // for ULong64_t
#include "TH1.h"        // For Histo actions
#include "TH2.h"        // For Histo actions
#include "TH3.h"        // For Histo actions
#include "TProfile.h"
#include "TProfile2D.h"
#include "TStatistic.h"

#include <algorithm>
#include <cstddef>
#include <initializer_list>
#include <limits>
#include <memory>
#include <sstream>
#include <stdexcept>
#include <string>
#include <type_traits> // is_same, enable_if
#include <typeinfo>
#include <vector>

class TGraph;

// Windows requires a forward decl of printValue to accept it as a valid friend function in RInterface
namespace ROOT {
void DisableImplicitMT();
bool IsImplicitMTEnabled();
void EnableImplicitMT(UInt_t numthreads);
class RDataFrame;
namespace Internal {
namespace RDF {
class GraphCreatorHelper;
}
}
}
namespace cling {
std::string printValue(ROOT::RDataFrame *tdf);
}

namespace ROOT {
namespace RDF {
namespace RDFDetail = ROOT::Detail::RDF;
namespace RDFInternal = ROOT::Internal::RDF;
namespace TTraits = ROOT::TypeTraits;

template <typename Proxied, typename DataSource>
class RInterface;

using RNode = RInterface<::ROOT::Detail::RDF::RNodeBase, void>;

// clang-format off
/**
 * \class ROOT::RDF::RInterface
 * \ingroup dataframe
 * \brief The public interface to the RDataFrame federation of classes
 * \tparam Proxied One of the "node" base types (e.g. RLoopManager, RFilterBase). The user never specifies this type manually.
 * \tparam DataSource The type of the RDataSource which is providing the data to the data frame. There is no source by default.
 *
 * The documentation of each method features a one liner illustrating how to use the method, for example showing how
 * the majority of the template parameters are automatically deduced requiring no or very little effort by the user.
 */
// clang-format on
template <typename Proxied, typename DataSource = void>
class RInterface {
   using DS_t = DataSource;
   using ColumnNames_t = RDFDetail::ColumnNames_t;
   using RFilterBase = RDFDetail::RFilterBase;
   using RRangeBase = RDFDetail::RRangeBase;
   using RLoopManager = RDFDetail::RLoopManager;
   friend std::string cling::printValue(::ROOT::RDataFrame *tdf); // For a nice printing at the prompt
   friend class RDFInternal::GraphDrawing::GraphCreatorHelper;

   template <typename T, typename W>
   friend class RInterface;

   std::shared_ptr<Proxied> fProxiedPtr; ///< Smart pointer to the graph node encapsulated by this RInterface.
   ///< The RLoopManager at the root of this computation graph. Never null.
   RLoopManager *fLoopManager;
   /// Non-owning pointer to a data-source object. Null if no data-source. RLoopManager has ownership of the object.
   RDataSource *fDataSource = nullptr;

   /// Contains the custom columns defined up to this node.
   RDFInternal::RBookedCustomColumns fCustomColumns;

public:
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Copy-assignment operator for RInterface.
   RInterface &operator=(const RInterface &) = default;

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Copy-ctor for RInterface.
   RInterface(const RInterface &) = default;

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Move-ctor for RInterface.
   RInterface(RInterface &&) = default;

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Only enabled when building a RInterface<RLoopManager>
   template <typename T = Proxied, typename std::enable_if<std::is_same<T, RLoopManager>::value, int>::type = 0>
   RInterface(const std::shared_ptr<Proxied> &proxied)
      : fProxiedPtr(proxied), fLoopManager(proxied.get()), fDataSource(proxied->GetDataSource())
   {
      AddDefaultColumns();
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Cast any RDataFrame node to a common type ROOT::RDF::RNode.
   /// Different RDataFrame methods return different C++ types. All nodes, however,
   /// can be cast to this common type at the cost of a small performance penalty.
   /// This allows, for example, storing RDataFrame nodes in a vector, or passing them
   /// around via (non-template, C++11) helper functions.
   /// Example usage:
   /// ~~~{.cpp}
   /// // a function that conditionally adds a Range to a RDataFrame node.
   /// RNode MaybeAddRange(RNode df, bool mustAddRange)
   /// {
   ///    return mustAddRange ? df.Range(1) : df;
   /// }
   /// // use as :
   /// ROOT::RDataFrame df(10);
   /// auto maybeRanged = MaybeAddRange(df, true);
   /// ~~~
   /// Note that it is not a problem to pass RNode's by value.
   operator RNode() const
   {
      return RNode(std::static_pointer_cast<::ROOT::Detail::RDF::RNodeBase>(fProxiedPtr), *fLoopManager, fCustomColumns,
                   fDataSource);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Append a filter to the call graph.
   /// \param[in] f Function, lambda expression, functor class or any other callable object. It must return a `bool`
   /// signalling whether the event has passed the selection (true) or not (false).
   /// \param[in] columns Names of the columns/branches in input to the filter function.
   /// \param[in] name Optional name of this filter. See `Report`.
   /// \return the filter node of the computation graph.
   ///
   /// Append a filter node at the point of the call graph corresponding to the
   /// object this method is called on.
   /// The callable `f` should not have side-effects (e.g. modification of an
   /// external or static variable) to ensure correct results when implicit
   /// multi-threading is active.
   ///
   /// RDataFrame only evaluates filters when necessary: if multiple filters
   /// are chained one after another, they are executed in order and the first
   /// one returning false causes the event to be discarded.
   /// Even if multiple actions or transformations depend on the same filter,
   /// it is executed once per entry. If its result is requested more than
   /// once, the cached result is served.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // C++ callable (function, functor class, lambda...) that takes two parameters of the types of "x" and "y"
   /// auto filtered = df.Filter(myCut, {"x", "y"});
   ///
   /// // String: it must contain valid C++ except that column names can be used instead of variable names
   /// auto filtered = df.Filter("x*y > 0");
   /// ~~~
   template <typename F, typename std::enable_if<!std::is_convertible<F, std::string>::value, int>::type = 0>
   RInterface<RDFDetail::RFilter<F, Proxied>, DS_t>
   Filter(F f, const ColumnNames_t &columns = {}, std::string_view name = "")
   {
      RDFInternal::CheckFilter(f);
      using ColTypes_t = typename TTraits::CallableTraits<F>::arg_types;
      constexpr auto nColumns = ColTypes_t::list_size;
      const auto validColumnNames = GetValidatedColumnNames(nColumns, columns);
      const auto newColumns =
         CheckAndFillDSColumns(validColumnNames, std::make_index_sequence<nColumns>(), ColTypes_t());

      using F_t = RDFDetail::RFilter<F, Proxied>;

      auto filterPtr = std::make_shared<F_t>(std::move(f), validColumnNames, fProxiedPtr, newColumns, name);
      fLoopManager->Book(filterPtr.get());
      return RInterface<F_t, DS_t>(std::move(filterPtr), *fLoopManager, newColumns, fDataSource);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Append a filter to the call graph.
   /// \param[in] f Function, lambda expression, functor class or any other callable object. It must return a `bool`
   /// signalling whether the event has passed the selection (true) or not (false).
   /// \param[in] name Optional name of this filter. See `Report`.
   /// \return the filter node of the computation graph.
   ///
   /// Refer to the first overload of this method for the full documentation.
   template <typename F, typename std::enable_if<!std::is_convertible<F, std::string>::value, int>::type = 0>
   RInterface<RDFDetail::RFilter<F, Proxied>, DS_t> Filter(F f, std::string_view name)
   {
      // The sfinae is there in order to pick up the overloaded method which accepts two strings
      // rather than this template method.
      return Filter(f, {}, name);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Append a filter to the call graph.
   /// \param[in] f Function, lambda expression, functor class or any other callable object. It must return a `bool`
   /// signalling whether the event has passed the selection (true) or not (false).
   /// \param[in] columns Names of the columns/branches in input to the filter function.
   /// \return the filter node of the computation graph.
   ///
   /// Refer to the first overload of this method for the full documentation.
   template <typename F>
   RInterface<RDFDetail::RFilter<F, Proxied>, DS_t> Filter(F f, const std::initializer_list<std::string> &columns)
   {
      return Filter(f, ColumnNames_t{columns});
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Append a filter to the call graph.
   /// \param[in] expression The filter expression in C++
   /// \param[in] name Optional name of this filter. See `Report`.
   /// \return the filter node of the computation graph.
   ///
   /// The expression is just-in-time compiled and used to filter entries. It must
   /// be valid C++ syntax in which variable names are substituted with the names
   /// of branches/columns.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto filtered_df = df.Filter("myCollection.size() > 3");
   /// auto filtered_name_df = df.Filter("myCollection.size() > 3", "Minumum collection size");
   /// ~~~
   RInterface<RDFDetail::RJittedFilter, DS_t> Filter(std::string_view expression, std::string_view name = "")
   {
      // deleted by the jitted call to JitFilterHelper
      auto upcastNodeOnHeap = RDFInternal::MakeSharedOnHeap(RDFInternal::UpcastNode(fProxiedPtr));
      using BaseNodeType_t = typename std::remove_pointer<decltype(upcastNodeOnHeap)>::type::element_type;
      RInterface<BaseNodeType_t> upcastInterface(*upcastNodeOnHeap, *fLoopManager, fCustomColumns, fDataSource);
      const auto jittedFilter = std::make_shared<RDFDetail::RJittedFilter>(fLoopManager, name);

      RDFInternal::BookFilterJit(jittedFilter.get(), upcastNodeOnHeap, name, expression, fLoopManager->GetAliasMap(),
                                 fLoopManager->GetBranchNames(), fCustomColumns, fLoopManager->GetTree(), fDataSource,
                                 fLoopManager->GetID());

      fLoopManager->Book(jittedFilter.get());
      return RInterface<RDFDetail::RJittedFilter, DS_t>(std::move(jittedFilter), *fLoopManager, fCustomColumns,
                                                        fDataSource);
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Creates a custom column
   /// \param[in] name The name of the custom column.
   /// \param[in] expression Function, lambda expression, functor class or any other callable object producing the temporary value. Returns the value that will be assigned to the custom column.
   /// \param[in] columns Names of the columns/branches in input to the producer function.
   /// \return the first node of the computation graph for which the new quantity is defined.
   ///
   /// Create a custom column that will be visible from all subsequent nodes
   /// of the functional chain. The `expression` is only evaluated for entries that pass
   /// all the preceding filters.
   /// A new variable is created called `name`, accessible as if it was contained
   /// in the dataset from subsequent transformations/actions.
   ///
   /// Use cases include:
   /// * caching the results of complex calculations for easy and efficient multiple access
   /// * extraction of quantities of interest from complex objects
   ///
   /// An exception is thrown if the name of the new column is already in use in this branch of the computation graph.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // assuming a function with signature:
   /// double myComplexCalculation(const RVec<float> &muon_pts);
   /// // we can pass it directly to Define
   /// auto df_with_define = df.Define("newColumn", myComplexCalculation, {"muon_pts"});
   /// // alternatively, we can pass the body of the function as a string, as in Filter:
   /// auto df_with_define = df.Define("newColumn", "x*x + y*y");
   /// ~~~
   template <typename F, typename std::enable_if<!std::is_convertible<F, std::string>::value, int>::type = 0>
   RInterface<Proxied, DS_t> Define(std::string_view name, F expression, const ColumnNames_t &columns = {})
   {
      return DefineImpl<F, RDFDetail::CustomColExtraArgs::None>(name, std::move(expression), columns);
   }
   // clang-format on

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Creates a custom column with a value dependent on the processing slot.
   /// \param[in] name The name of the custom column.
   /// \param[in] expression Function, lambda expression, functor class or any other callable object producing the temporary value. Returns the value that will be assigned to the custom column.
   /// \param[in] columns Names of the columns/branches in input to the producer function (excluding the slot number).
   /// \return the first node of the computation graph for which the new quantity is defined.
   ///
   /// This alternative implementation of `Define` is meant as a helper in writing thread-safe custom columns.
   /// The expression must be a callable of signature R(unsigned int, T1, T2, ...) where `T1, T2...` are the types
   /// of the columns that the expression takes as input. The first parameter is reserved for an unsigned integer
   /// representing a "slot number". RDataFrame guarantees that different threads will invoke the expression with
   /// different slot numbers - slot numbers will range from zero to ROOT::GetImplicitMTPoolSize()-1.
   ///
   /// The following two calls are equivalent, although `DefineSlot` is slightly more performant:
   /// ~~~{.cpp}
   /// int function(unsigned int, double, double);
   /// df.Define("x", function, {"rdfslot_", "column1", "column2"})
   /// df.DefineSlot("x", function, {"column1", "column2"})
   /// ~~~
   ///
   /// See Define for more information.
   template <typename F>
   RInterface<Proxied, DS_t> DefineSlot(std::string_view name, F expression, const ColumnNames_t &columns = {})
   {
      return DefineImpl<F, RDFDetail::CustomColExtraArgs::Slot>(name, std::move(expression), columns);
   }
   // clang-format on

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Creates a custom column with a value dependent on the processing slot and the current entry.
   /// \param[in] name The name of the custom column.
   /// \param[in] expression Function, lambda expression, functor class or any other callable object producing the temporary value. Returns the value that will be assigned to the custom column.
   /// \param[in] columns Names of the columns/branches in input to the producer function (excluding slot and entry).
   /// \return the first node of the computation graph for which the new quantity is defined.
   ///
   /// This alternative implementation of `Define` is meant as a helper in writing entry-specific, thread-safe custom
   /// columns. The expression must be a callable of signature R(unsigned int, ULong64_t, T1, T2, ...) where `T1, T2...`
   /// are the types of the columns that the expression takes as input. The first parameter is reserved for an unsigned
   /// integer representing a "slot number". RDataFrame guarantees that different threads will invoke the expression with
   /// different slot numbers - slot numbers will range from zero to ROOT::GetImplicitMTPoolSize()-1. The second parameter
   /// is reserved for a `ULong64_t` representing the current entry being processed by the current thread.
   ///
   /// The following two `Define`s are equivalent, although `DefineSlotEntry` is slightly more performant:
   /// ~~~{.cpp}
   /// int function(unsigned int, ULong64_t, double, double);
   /// Define("x", function, {"rdfslot_", "rdfentry_", "column1", "column2"})
   /// DefineSlotEntry("x", function, {"column1", "column2"})
   /// ~~~
   ///
   /// See Define for more information.
   template <typename F>
   RInterface<Proxied, DS_t> DefineSlotEntry(std::string_view name, F expression, const ColumnNames_t &columns = {})
   {
      return DefineImpl<F, RDFDetail::CustomColExtraArgs::SlotAndEntry>(name, std::move(expression), columns);
   }
   // clang-format on

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Creates a custom column
   /// \param[in] name The name of the custom column.
   /// \param[in] expression An expression in C++ which represents the temporary value
   /// \return the first node of the computation graph for which the new quantity is defined.
   ///
   /// The expression is just-in-time compiled and used to produce the column entries.
   /// It must be valid C++ syntax in which variable names are substituted with the names
   /// of branches/columns.
   ///
   /// Refer to the first overload of this method for the full documentation.
   RInterface<Proxied, DS_t> Define(std::string_view name, std::string_view expression)
   {
      // this check must be done before jitting lest we throw exceptions in jitted code
      RDFInternal::CheckCustomColumn(name, fLoopManager->GetTree(), fCustomColumns.GetNames(),
                                     fLoopManager->GetAliasMap(),
                                     fDataSource ? fDataSource->GetColumnNames() : ColumnNames_t{});

      auto jittedCustomColumn =
         std::make_shared<RDFDetail::RJittedCustomColumn>(fLoopManager, name, fLoopManager->GetNSlots());

      RDFInternal::BookDefineJit(name, expression, *fLoopManager, fDataSource, jittedCustomColumn, fCustomColumns,
                                 fLoopManager->GetBranchNames());

      RDFInternal::RBookedCustomColumns newCols(fCustomColumns);
      newCols.AddName(name);
      newCols.AddColumn(jittedCustomColumn, name);

      fLoopManager->RegisterCustomColumn(jittedCustomColumn.get());

      RInterface<Proxied, DS_t> newInterface(fProxiedPtr, *fLoopManager, std::move(newCols), fDataSource);

      return newInterface;
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Allow to refer to a column with a different name
   /// \param[in] alias name of the column alias
   /// \param[in] columnName of the column to be aliased
   /// \return the first node of the computation graph for which the alias is available.
   ///
   /// Aliasing an alias is supported.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto df_with_alias = df.Alias("simple_name", "very_long&complex_name!!!");
   /// ~~~
   RInterface<Proxied, DS_t> Alias(std::string_view alias, std::string_view columnName)
   {
      // The symmetry with Define is clear. We want to:
      // - Create globally the alias and return this very node, unchanged
      // - Make aliases accessible based on chains and not globally

      // Helper to find out if a name is a column
      auto &dsColumnNames = fDataSource ? fDataSource->GetColumnNames() : ColumnNames_t{};

      // If the alias name is a column name, there is a problem
      RDFInternal::CheckCustomColumn(alias, fLoopManager->GetTree(), fCustomColumns.GetNames(),
                                     fLoopManager->GetAliasMap(), dsColumnNames);

      const auto validColumnName = GetValidatedColumnNames(1, {std::string(columnName)})[0];

      fLoopManager->AddColumnAlias(std::string(alias), validColumnName);

      RDFInternal::RBookedCustomColumns newCols(fCustomColumns);

      newCols.AddName(alias);
      RInterface<Proxied, DS_t> newInterface(fProxiedPtr, *fLoopManager, std::move(newCols), fDataSource);

      return newInterface;
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns to disk, in a new TTree `treename` in file `filename`.
   /// \tparam ColumnTypes variadic list of branch/column types.
   /// \param[in] treename The name of the output TTree.
   /// \param[in] filename The name of the output TFile.
   /// \param[in] columnList The list of names of the columns/branches to be written.
   /// \param[in] options RSnapshotOptions struct with extra options to pass to TFile and TTree.
   /// \return a `RDataFrame` that wraps the snapshotted dataset.
   ///
   /// Support for writing of nested branches is limited (although RDataFrame is able to read them) and dot ('.')
   /// characters in input column names will be replaced by underscores ('_') in the branches produced by Snapshot.
   /// When writing a variable size array through Snapshot, it is required that the column indicating its size is also
   /// written out and it appears before the array in the columnList.
   ///
   /// ### Example invocations:
   ///
   /// ~~~{.cpp}
   /// // without specifying template parameters (column types automatically deduced)
   /// df.Snapshot("outputTree", "outputFile.root", {"x", "y"});
   ///
   /// // specifying template parameters ("x" is `int`, "y" is `float`)
   /// df.Snapshot<int, float>("outputTree", "outputFile.root", {"x", "y"});
   /// ~~~
   ///
   /// To book a Snapshot without triggering the event loop, one needs to set the appropriate flag in
   /// `RSnapshotOptions`:
   /// ~~~{.cpp}
   /// RSnapshotOptions opts;
   /// opts.fLazy = true;
   /// df.Snapshot("outputTree", "outputFile.root", {"x"}, opts);
   /// ~~~
   template <typename... ColumnTypes>
   RResultPtr<RInterface<RLoopManager>>
   Snapshot(std::string_view treename, std::string_view filename, const ColumnNames_t &columnList,
            const RSnapshotOptions &options = RSnapshotOptions())
   {
      return SnapshotImpl<ColumnTypes...>(treename, filename, columnList, options);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns to disk, in a new TTree `treename` in file `filename`.
   /// \param[in] treename The name of the output TTree.
   /// \param[in] filename The name of the output TFile.
   /// \param[in] columnList The list of names of the columns/branches to be written.
   /// \param[in] options RSnapshotOptions struct with extra options to pass to TFile and TTree.
   /// \return a `RDataFrame` that wraps the snapshotted dataset.
   ///
   /// This function returns a `RDataFrame` built with the output tree as a source.
   /// The types of the columns are automatically inferred and do not need to be specified.
   ///
   /// See above for a more complete description and example usages.
   RResultPtr<RInterface<RLoopManager>> Snapshot(std::string_view treename, std::string_view filename,
                                                 const ColumnNames_t &columnList,
                                                 const RSnapshotOptions &options = RSnapshotOptions())
   {
      // Early return: if the list of columns is empty, just return an empty RDF
      // If we proceed, the jitted call will not compile!
      if (columnList.empty()) {
         auto nEntries = *this->Count();
         auto snapshotRDF = std::make_shared<RInterface<RLoopManager>>(std::make_shared<RLoopManager>(nEntries));
         return MakeResultPtr(snapshotRDF, *fLoopManager, nullptr);
      }
      auto tree = fLoopManager->GetTree();
      const auto nsID = fLoopManager->GetID();
      std::stringstream snapCall;
      auto upcastNode = RDFInternal::UpcastNode(fProxiedPtr);
      RInterface<TTraits::TakeFirstParameter_t<decltype(upcastNode)>> upcastInterface(fProxiedPtr, *fLoopManager,
                                                                                      fCustomColumns, fDataSource);

      // build a string equivalent to
      // "resPtr = (RInterface<nodetype*>*)(this)->Snapshot<Ts...>(args...)"
      RResultPtr<RInterface<RLoopManager>> resPtr;
      snapCall << "*reinterpret_cast<ROOT::RDF::RResultPtr<ROOT::RDF::RInterface<ROOT::Detail::RDF::RLoopManager>>*>("
               << RDFInternal::PrettyPrintAddr(&resPtr)
               << ") = reinterpret_cast<ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase>*>("
               << RDFInternal::PrettyPrintAddr(&upcastInterface) << ")->Snapshot<";

      const auto &customCols = fCustomColumns.GetNames();
      const auto dontConvertVector = false;

      const auto validColumnNames = GetValidatedColumnNames(columnList.size(), columnList);

      for (auto &c : validColumnNames) {
         const auto isCustom = std::find(customCols.begin(), customCols.end(), c) != customCols.end();
         const auto customColID = isCustom ? fCustomColumns.GetColumns().at(c)->GetID() : 0;
         snapCall << RDFInternal::ColumnName2ColumnTypeName(c, nsID, tree, fDataSource, isCustom, dontConvertVector,
                                                            customColID)
                  << ", ";
      };
      if (!columnList.empty())
         snapCall.seekp(-2, snapCall.cur); // remove the last ",
      snapCall << ">(\"" << treename << "\", \"" << filename << "\", "
               << "*reinterpret_cast<std::vector<std::string>*>(" // vector<string> should be ColumnNames_t
               << RDFInternal::PrettyPrintAddr(&columnList) << "),"
               << "*reinterpret_cast<ROOT::RDF::RSnapshotOptions*>(" << RDFInternal::PrettyPrintAddr(&options) << "));";
      // jit snapCall, return result
      fLoopManager->JitDeclarations(); // some type aliases might be needed by the code jitted in the next line
      RDFInternal::InterpreterCalc(snapCall.str(), "Snapshot");
      return resPtr;
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns to disk, in a new TTree `treename` in file `filename`.
   /// \param[in] treename The name of the output TTree.
   /// \param[in] filename The name of the output TFile.
   /// \param[in] columnNameRegexp The regular expression to match the column names to be selected. The presence of a '^' and a '$' at the end of the string is implicitly assumed if they are not specified. The dialect supported is PCRE via the TPRegexp class. An empty string signals the selection of all columns.
   /// \param[in] options RSnapshotOptions struct with extra options to pass to TFile and TTree
   /// \return a `RDataFrame` that wraps the snapshotted dataset.
   ///
   /// This function returns a `RDataFrame` built with the output tree as a source.
   /// The types of the columns are automatically inferred and do not need to be specified.
   ///
   /// See above for a more complete description and example usages.
   RResultPtr<RInterface<RLoopManager>> Snapshot(std::string_view treename, std::string_view filename,
                                                 std::string_view columnNameRegexp = "",
                                                 const RSnapshotOptions &options = RSnapshotOptions())
   {
      auto selectedColumns = RDFInternal::ConvertRegexToColumns(fCustomColumns,
                                                                fLoopManager->GetTree(),
                                                                fDataSource,
                                                                columnNameRegexp,
                                                                "Snapshot");
      return Snapshot(treename, filename, selectedColumns, options);
   }
   // clang-format on

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns to disk, in a new TTree `treename` in file `filename`.
   /// \param[in] treename The name of the output TTree.
   /// \param[in] filename The name of the output TFile.
   /// \param[in] columnList The list of names of the columns/branches to be written.
   /// \param[in] options RSnapshotOptions struct with extra options to pass to TFile and TTree.
   /// \return a `RDataFrame` that wraps the snapshotted dataset.
   ///
   /// This function returns a `RDataFrame` built with the output tree as a source.
   /// The types of the columns are automatically inferred and do not need to be specified.
   ///
   /// See above for a more complete description and example usages.
   RResultPtr<RInterface<RLoopManager>> Snapshot(std::string_view treename, std::string_view filename,
                                                 std::initializer_list<std::string> columnList,
                                                 const RSnapshotOptions &options = RSnapshotOptions())
   {
      ColumnNames_t selectedColumns(columnList);
      return Snapshot(treename, filename, selectedColumns, options);
   }
   // clang-format on

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns in memory
   /// \tparam ColumnTypes variadic list of branch/column types.
   /// \param[in] columns to be cached in memory.
   /// \return a `RDataFrame` that wraps the cached dataset.
   ///
   /// This action returns a new `RDataFrame` object, completely detached from
   /// the originating `RDataFrame`. The new dataframe only contains the cached
   /// columns and stores their content in memory for fast, zero-copy subsequent access.
   ///
   /// Use `Cache` if you know you will only need a subset of the (`Filter`ed) data that
   /// fits in memory and that will be accessed many times.
   ///
   /// ### Example usage:
   ///
   /// **Types and columns specified:**
   /// ~~~{.cpp}
   /// auto cache_some_cols_df = df.Cache<double, MyClass, int>({"col0", "col1", "col2"});
   /// ~~~
   ///
   /// **Types inferred and columns specified (this invocation relies on jitting):**
   /// ~~~{.cpp}
   /// auto cache_some_cols_df = df.Cache({"col0", "col1", "col2"});
   /// ~~~
   ///
   /// **Types inferred and columns selected with a regexp (this invocation relies on jitting):**
   /// ~~~{.cpp}
   /// auto cache_all_cols_df = df.Cache(myRegexp);
   /// ~~~
   template <typename... ColumnTypes>
   RInterface<RLoopManager> Cache(const ColumnNames_t &columnList)
   {
      auto staticSeq = std::make_index_sequence<sizeof...(ColumnTypes)>();
      return CacheImpl<ColumnTypes...>(columnList, staticSeq);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns in memory
   /// \param[in] columns to be cached in memory
   /// \return a `RDataFrame` that wraps the cached dataset.
   ///
   /// See the previous overloads for more information.
   RInterface<RLoopManager> Cache(const ColumnNames_t &columnList)
   {
      // Early return: if the list of columns is empty, just return an empty RDF
      // If we proceed, the jitted call will not compile!
      if (columnList.empty()) {
         auto nEntries = *this->Count();
         RInterface<RLoopManager> emptyRDF(std::make_shared<RLoopManager>(nEntries));
         return emptyRDF;
      }

      auto tree = fLoopManager->GetTree();
      const auto nsID = fLoopManager->GetID();
      std::stringstream cacheCall;
      auto upcastNode = RDFInternal::UpcastNode(fProxiedPtr);
      RInterface<TTraits::TakeFirstParameter_t<decltype(upcastNode)>> upcastInterface(fProxiedPtr, *fLoopManager,
                                                                                      fCustomColumns, fDataSource);
      // build a string equivalent to
      // "(RInterface<nodetype*>*)(this)->Cache<Ts...>(*(ColumnNames_t*)(&columnList))"
      RInterface<RLoopManager> resRDF(std::make_shared<ROOT::Detail::RDF::RLoopManager>(0));
      cacheCall << "*reinterpret_cast<ROOT::RDF::RInterface<ROOT::Detail::RDF::RLoopManager>*>("
                << RDFInternal::PrettyPrintAddr(&resRDF)
                << ") = reinterpret_cast<ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase>*>("
                << RDFInternal::PrettyPrintAddr(&upcastInterface) << ")->Cache<";

      const auto &customCols = fCustomColumns.GetNames();
      for (auto &c : columnList) {
         const auto isCustom = std::find(customCols.begin(), customCols.end(), c) != customCols.end();
         const auto customColID = isCustom ? fCustomColumns.GetColumns().at(c)->GetID() : 0;
         cacheCall << RDFInternal::ColumnName2ColumnTypeName(c, nsID, tree, fDataSource, isCustom,
                                                             /*vector2rvec=*/true, customColID)
                   << ", ";
      };
      if (!columnList.empty())
         cacheCall.seekp(-2, cacheCall.cur);                         // remove the last ",
      cacheCall << ">(*reinterpret_cast<std::vector<std::string>*>(" // vector<string> should be ColumnNames_t
                << RDFInternal::PrettyPrintAddr(&columnList) << "));";
      // jit cacheCall, return result
      fLoopManager->JitDeclarations(); // some type aliases might be needed by the code jitted in the next line
      RDFInternal::InterpreterCalc(cacheCall.str(), "Cache");
      return resRDF;
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns in memory
   /// \param[in] columnNameRegexp The regular expression to match the column names to be selected. The presence of a '^' and a '$' at the end of the string is implicitly assumed if they are not specified. The dialect supported is PCRE via the TPRegexp class. An empty string signals the selection of all columns.
   /// \return a `RDataFrame` that wraps the cached dataset.
   ///
   /// The existing columns are matched against the regular expression. If the string provided
   /// is empty, all columns are selected. See the previous overloads for more information.
   RInterface<RLoopManager> Cache(std::string_view columnNameRegexp = "")
   {

      auto selectedColumns = RDFInternal::ConvertRegexToColumns(fCustomColumns, fLoopManager->GetTree(), fDataSource,
                                                                columnNameRegexp, "Cache");
      return Cache(selectedColumns);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Save selected columns in memory
   /// \param[in] columns to be cached in memory.
   /// \return a `RDataFrame` that wraps the cached dataset.
   ///
   /// See the previous overloads for more information.
   RInterface<RLoopManager> Cache(std::initializer_list<std::string> columnList)
   {
      ColumnNames_t selectedColumns(columnList);
      return Cache(selectedColumns);
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Creates a node that filters entries based on range: [begin, end)
   /// \param[in] begin Initial entry number considered for this range.
   /// \param[in] end Final entry number (excluded) considered for this range. 0 means that the range goes until the end of the dataset.
   /// \param[in] stride Process one entry of the [begin, end) range every `stride` entries. Must be strictly greater than 0.
   /// \return the first node of the computation graph for which the event loop is limited to a certain range of entries.
   ///
   /// Note that in case of previous Ranges and Filters the selected range refers to the transformed dataset.
   /// Ranges are only available if EnableImplicitMT has _not_ been called. Multi-thread ranges are not supported.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto d_0_30 = d.Range(0, 30); // Pick the first 30 entries
   /// auto d_15_end = d.Range(15, 0); // Pick all entries from 15 onwards
   /// auto d_15_end_3 = d.Range(15, 0, 3); // Stride: from event 15, pick an event every 3
   /// ~~~
   // clang-format on
   RInterface<RDFDetail::RRange<Proxied>, DS_t> Range(unsigned int begin, unsigned int end, unsigned int stride = 1)
   {
      // check invariants
      if (stride == 0 || (end != 0 && end < begin))
         throw std::runtime_error("Range: stride must be strictly greater than 0 and end must be greater than begin.");
      CheckIMTDisabled("Range");

      using Range_t = RDFDetail::RRange<Proxied>;
      auto rangePtr = std::make_shared<Range_t>(begin, end, stride, fProxiedPtr);
      fLoopManager->Book(rangePtr.get());
      RInterface<RDFDetail::RRange<Proxied>> tdf_r(std::move(rangePtr), *fLoopManager, fCustomColumns, fDataSource);
      return tdf_r;
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Creates a node that filters entries based on range
   /// \param[in] end Final entry number (excluded) considered for this range. 0 means that the range goes until the end of the dataset.
   /// \return a node of the computation graph for which the range is defined.
   ///
   /// See the other Range overload for a detailed description.
   // clang-format on
   RInterface<RDFDetail::RRange<Proxied>, DS_t> Range(unsigned int end) { return Range(0, end, 1); }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Execute a user-defined function on each entry (*instant action*)
   /// \param[in] f Function, lambda expression, functor class or any other callable object performing user defined calculations.
   /// \param[in] columns Names of the columns/branches in input to the user function.
   ///
   /// The callable `f` is invoked once per entry. This is an *instant action*:
   /// upon invocation, an event loop as well as execution of all scheduled actions
   /// is triggered.
   /// Users are responsible for the thread-safety of this callable when executing
   /// with implicit multi-threading enabled (i.e. ROOT::EnableImplicitMT).
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// myDf.Foreach([](int i){ std::cout << i << std::endl;}, {"myIntColumn"});
   /// ~~~
   // clang-format on
   template <typename F>
   void Foreach(F f, const ColumnNames_t &columns = {})
   {
      using arg_types = typename TTraits::CallableTraits<decltype(f)>::arg_types_nodecay;
      using ret_type = typename TTraits::CallableTraits<decltype(f)>::ret_type;
      ForeachSlot(RDFInternal::AddSlotParameter<ret_type>(f, arg_types()), columns);
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Execute a user-defined function requiring a processing slot index on each entry (*instant action*)
   /// \param[in] f Function, lambda expression, functor class or any other callable object performing user defined calculations.
   /// \param[in] columns Names of the columns/branches in input to the user function.
   ///
   /// Same as `Foreach`, but the user-defined function takes an extra
   /// `unsigned int` as its first parameter, the *processing slot index*.
   /// This *slot index* will be assigned a different value, `0` to `poolSize - 1`,
   /// for each thread of execution.
   /// This is meant as a helper in writing thread-safe `Foreach`
   /// actions when using `RDataFrame` after `ROOT::EnableImplicitMT()`.
   /// The user-defined processing callable is able to follow different
   /// *streams of processing* indexed by the first parameter.
   /// `ForeachSlot` works just as well with single-thread execution: in that
   /// case `slot` will always be `0`.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// myDf.ForeachSlot([](unsigned int s, int i){ std::cout << "Slot " << s << ": "<< i << std::endl;}, {"myIntColumn"});
   /// ~~~
   // clang-format on
   template <typename F>
   void ForeachSlot(F f, const ColumnNames_t &columns = {})
   {
      using ColTypes_t = TypeTraits::RemoveFirstParameter_t<typename TTraits::CallableTraits<F>::arg_types>;
      constexpr auto nColumns = ColTypes_t::list_size;

      const auto validColumnNames = GetValidatedColumnNames(nColumns, columns);

      auto newColumns = CheckAndFillDSColumns(validColumnNames, std::make_index_sequence<nColumns>(), ColTypes_t());

      using Helper_t = RDFInternal::ForeachSlotHelper<F>;
      using Action_t = RDFInternal::RAction<Helper_t, Proxied>;

      auto action =
         std::make_unique<Action_t>(Helper_t(std::move(f)), validColumnNames, fProxiedPtr, std::move(newColumns));
      fLoopManager->Book(action.get());

      fLoopManager->Run();
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Execute a user-defined reduce operation on the values of a column.
   /// \tparam F The type of the reduce callable. Automatically deduced.
   /// \tparam T The type of the column to apply the reduction to. Automatically deduced.
   /// \param[in] f A callable with signature `T(T,T)`
   /// \param[in] columnName The column to be reduced. If omitted, the first default column is used instead.
   /// \return the reduced quantity wrapped in a `RResultPtr`.
   ///
   /// A reduction takes two values of a column and merges them into one (e.g.
   /// by summing them, taking the maximum, etc). This action performs the
   /// specified reduction operation on all processed column values, returning
   /// a single value of the same type. The callable f must satisfy the general
   /// requirements of a *processing function* besides having signature `T(T,T)`
   /// where `T` is the type of column columnName.
   ///
   /// The returned reduced value of each thread (e.g. the initial value of a sum) is initialized to a
   /// default-constructed T object. This is commonly expected to be the neutral/identity element for the specific
   /// reduction operation `f` (e.g. 0 for a sum, 1 for a product). If a default-constructed T does not satisfy this
   /// requirement, users should explicitly specify an initialization value for T by calling the appropriate `Reduce`
   /// overload.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto sumOfIntCol = d.Reduce([](int x, int y) { return x + y; }, "intCol");
   /// ~~~
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   // clang-format on
   template <typename F, typename T = typename TTraits::CallableTraits<F>::ret_type>
   RResultPtr<T> Reduce(F f, std::string_view columnName = "")
   {
      static_assert(
         std::is_default_constructible<T>::value,
         "reduce object cannot be default-constructed. Please provide an initialisation value (redIdentity)");
      return Reduce(std::move(f), columnName, T());
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Execute a user-defined reduce operation on the values of a column.
   /// \tparam F The type of the reduce callable. Automatically deduced.
   /// \tparam T The type of the column to apply the reduction to. Automatically deduced.
   /// \param[in] f A callable with signature `T(T,T)`
   /// \param[in] columnName The column to be reduced. If omitted, the first default column is used instead.
   /// \param[in] redIdentity The reduced object of each thread is initialised to this value.
   /// \return the reduced quantity wrapped in a `RResultPtr`.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto sumOfIntColWithOffset = d.Reduce([](int x, int y) { return x + y; }, "intCol", 42);
   /// ~~~
   /// See the description of the first Reduce overload for more information.
   template <typename F, typename T = typename TTraits::CallableTraits<F>::ret_type>
   RResultPtr<T> Reduce(F f, std::string_view columnName, const T &redIdentity)
   {
      return Aggregate(f, f, columnName, redIdentity);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return the number of entries processed (*lazy action*)
   /// \return the number of entries wrapped in a `RResultPtr`.
   ///
   /// Useful e.g. for counting the number of entries passing a certain filter (see also `Report`).
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto nEntriesAfterCuts = myFilteredDf.Count();
   /// ~~~
   ///
   RResultPtr<ULong64_t> Count()
   {
      const auto nSlots = fLoopManager->GetNSlots();
      auto cSPtr = std::make_shared<ULong64_t>(0);
      using Helper_t = RDFInternal::CountHelper;
      using Action_t = RDFInternal::RAction<Helper_t, Proxied>;
      auto action =
         std::make_unique<Action_t>(Helper_t(cSPtr, nSlots), ColumnNames_t({}), fProxiedPtr, std::move(fCustomColumns));
      fLoopManager->Book(action.get());
      return MakeResultPtr(cSPtr, *fLoopManager, std::move(action));
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return a collection of values of a column (*lazy action*, returns a std::vector by default)
   /// \tparam T The type of the column.
   /// \tparam COLL The type of collection used to store the values.
   /// \param[in] column The name of the column to collect the values of.
   /// \return the content of the selected column wrapped in a `RResultPtr`.
   ///
   /// The collection type to be specified for C-style array columns is `RVec<T>`:
   /// in this case the returned collection is a `std::vector<RVec<T>>`.
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // In this case intCol is a std::vector<int>
   /// auto intCol = rdf.Take<int>("integerColumn");
   /// // Same content as above but in this case taken as a RVec<int>
   /// auto intColAsRVec = rdf.Take<int, RVec<int>>("integerColumn");
   /// // In this case intCol is a std::vector<RVec<int>>, a collection of collections
   /// auto cArrayIntCol = rdf.Take<RVec<int>>("cArrayInt");
   /// ~~~
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   template <typename T, typename COLL = std::vector<T>>
   RResultPtr<COLL> Take(std::string_view column = "")
   {
      const auto columns = column.empty() ? ColumnNames_t() : ColumnNames_t({std::string(column)});

      const auto validColumnNames = GetValidatedColumnNames(1, columns);

      auto newColumns = CheckAndFillDSColumns(validColumnNames, std::make_index_sequence<1>(), TTraits::TypeList<T>());

      using Helper_t = RDFInternal::TakeHelper<T, T, COLL>;
      using Action_t = RDFInternal::RAction<Helper_t, Proxied>;
      auto valuesPtr = std::make_shared<COLL>();
      const auto nSlots = fLoopManager->GetNSlots();

      auto action =
         std::make_unique<Action_t>(Helper_t(valuesPtr, nSlots), validColumnNames, fProxiedPtr, std::move(newColumns));
      fLoopManager->Book(action.get());
      return MakeResultPtr(valuesPtr, *fLoopManager, std::move(action));
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a one-dimensional histogram with the values of a column (*lazy action*)
   /// \tparam V The type of the column used to fill the histogram.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \param[in] vName The name of the column that will fill the histogram.
   /// \return the monodimensional histogram wrapped in a `RResultPtr`.
   ///
   /// Columns can be of a container type (e.g. `std::vector<double>`), in which case the histogram
   /// is filled with each one of the elements of the container. In case multiple columns of container type
   /// are provided (e.g. values and weights) they must have the same length for each one of the events (but
   /// possibly different lengths between events).
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo1D({"histName", "histTitle", 64u, 0., 128.}, "myColumn");
   /// // Explicit column type
   /// auto myHist2 = myDf.Histo1D<float>({"histName", "histTitle", 64u, 0., 128.}, "myColumn");
   /// ~~~
   ///
   template <typename V = RDFDetail::RInferredType>
   RResultPtr<::TH1D> Histo1D(const TH1DModel &model = {"", "", 128u, 0., 0.}, std::string_view vName = "")
   {
      const auto userColumns = vName.empty() ? ColumnNames_t() : ColumnNames_t({std::string(vName)});

      const auto validatedColumns = GetValidatedColumnNames(1, userColumns);

      std::shared_ptr<::TH1D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetHistogram();
         h->SetDirectory(nullptr);
      }

      if (h->GetXaxis()->GetXmax() == h->GetXaxis()->GetXmin())
         RDFInternal::HistoUtils<::TH1D>::SetCanExtendAllAxes(*h);
      return CreateAction<RDFInternal::ActionTags::Histo1D, V>(validatedColumns, h);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a one-dimensional histogram with the values of a column (*lazy action*)
   /// \tparam V The type of the column used to fill the histogram.
   /// \param[in] vName The name of the column that will fill the histogram.
   /// \return the monodimensional histogram wrapped in a `RResultPtr`.
   ///
   /// This overload uses a default model histogram TH1D(name, title, 128u, 0., 0.).
   /// The "name" and "title" strings are built starting from the input column name.
   /// See the description of the first Histo1D overload for more details.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo1D("myColumn");
   /// // Explicit column type
   /// auto myHist2 = myDf.Histo1D<float>("myColumn");
   /// ~~~
   ///
   template <typename V = RDFDetail::RInferredType>
   RResultPtr<::TH1D> Histo1D(std::string_view vName)
   {
      const auto h_name = std::string(vName);
      const auto h_title = h_name + ";" + h_name + ";count";
      return Histo1D<V>({h_name.c_str(), h_title.c_str(), 128u, 0., 0.}, vName);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a one-dimensional histogram with the weighted values of a column (*lazy action*)
   /// \tparam V The type of the column used to fill the histogram.
   /// \tparam W The type of the column used as weights.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \param[in] vName The name of the column that will fill the histogram.
   /// \param[in] wName The name of the column that will provide the weights.
   /// \return the monodimensional histogram wrapped in a `RResultPtr`.
   ///
   /// See the description of the first Histo1D overload for more details.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo1D({"histName", "histTitle", 64u, 0., 128.}, "myValue", "myweight");
   /// // Explicit column type
   /// auto myHist2 = myDf.Histo1D<float, int>({"histName", "histTitle", 64u, 0., 128.}, "myValue", "myweight");
   /// ~~~
   ///
   template <typename V = RDFDetail::RInferredType, typename W = RDFDetail::RInferredType>
   RResultPtr<::TH1D> Histo1D(const TH1DModel &model, std::string_view vName, std::string_view wName)
   {
      const std::vector<std::string_view> columnViews = {vName, wName};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      std::shared_ptr<::TH1D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetHistogram();
      }
      return CreateAction<RDFInternal::ActionTags::Histo1D, V, W>(userColumns, h);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a one-dimensional histogram with the weighted values of a column (*lazy action*)
   /// \tparam V The type of the column used to fill the histogram.
   /// \tparam W The type of the column used as weights.
   /// \param[in] vName The name of the column that will fill the histogram.
   /// \param[in] wName The name of the column that will provide the weights.
   /// \return the monodimensional histogram wrapped in a `RResultPtr`.
   ///
   /// This overload uses a default model histogram TH1D(name, title, 128u, 0., 0.).
   /// The "name" and "title" strings are built starting from the input column names.
   /// See the description of the first Histo1D overload for more details.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo1D("myValue", "myweight");
   /// // Explicit column types
   /// auto myHist2 = myDf.Histo1D<float, int>("myValue", "myweight");
   /// ~~~
   ///
   template <typename V = RDFDetail::RInferredType, typename W = RDFDetail::RInferredType>
   RResultPtr<::TH1D> Histo1D(std::string_view vName, std::string_view wName)
   {
      // We build name and title based on the value and weight column names
      std::string str_vName{vName};
      std::string str_wName{wName};
      const auto h_name = str_vName + "_weighted_" + str_wName;
      const auto h_title = str_vName + ", weights: " + str_wName + ";" + str_vName + ";count * " + str_wName;
      return Histo1D<V, W>({h_name.c_str(), h_title.c_str(), 128u, 0., 0.}, vName, wName);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a one-dimensional histogram with the weighted values of a column (*lazy action*)
   /// \tparam V The type of the column used to fill the histogram.
   /// \tparam W The type of the column used as weights.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \return the monodimensional histogram wrapped in a `RResultPtr`.
   ///
   /// This overload will use the first two default columns as column names.
   /// See the description of the first Histo1D overload for more details.
   template <typename V, typename W>
   RResultPtr<::TH1D> Histo1D(const TH1DModel &model = {"", "", 128u, 0., 0.})
   {
      return Histo1D<V, W>(model, "", "");
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a two-dimensional histogram (*lazy action*)
   /// \tparam V1 The type of the column used to fill the x axis of the histogram.
   /// \tparam V2 The type of the column used to fill the y axis of the histogram.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \return the bidimensional histogram wrapped in a `RResultPtr`.
   ///
   /// Columns can be of a container type (e.g. std::vector<double>), in which case the histogram
   /// is filled with each one of the elements of the container. In case multiple columns of container type
   /// are provided (e.g. values and weights) they must have the same length for each one of the events (but
   /// possibly different lengths between events).
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo2D({"histName", "histTitle", 64u, 0., 128., 32u, -4., 4.}, "myValueX", "myValueY");
   /// // Explicit column types
   /// auto myHist2 = myDf.Histo2D<float, float>({"histName", "histTitle", 64u, 0., 128., 32u, -4., 4.}, "myValueX", "myValueY");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType>
   RResultPtr<::TH2D> Histo2D(const TH2DModel &model, std::string_view v1Name = "", std::string_view v2Name = "")
   {
      std::shared_ptr<::TH2D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetHistogram();
      }
      if (!RDFInternal::HistoUtils<::TH2D>::HasAxisLimits(*h)) {
         throw std::runtime_error("2D histograms with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Histo2D, V1, V2>(userColumns, h);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a weighted two-dimensional histogram (*lazy action*)
   /// \tparam V1 The type of the column used to fill the x axis of the histogram.
   /// \tparam V2 The type of the column used to fill the y axis of the histogram.
   /// \tparam W The type of the column used for the weights of the histogram.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \param[in] wName The name of the column that will provide the weights.
   /// \return the bidimensional histogram wrapped in a `RResultPtr`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   /// The user gives up ownership of the model histogram.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo2D({"histName", "histTitle", 64u, 0., 128., 32u, -4., 4.}, "myValueX", "myValueY", "myWeight");
   /// // Explicit column types
   /// auto myHist2 = myDf.Histo2D<float, float, double>({"histName", "histTitle", 64u, 0., 128., 32u, -4., 4.}, "myValueX", "myValueY", "myWeight");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType,
             typename W = RDFDetail::RInferredType>
   RResultPtr<::TH2D>
   Histo2D(const TH2DModel &model, std::string_view v1Name, std::string_view v2Name, std::string_view wName)
   {
      std::shared_ptr<::TH2D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetHistogram();
      }
      if (!RDFInternal::HistoUtils<::TH2D>::HasAxisLimits(*h)) {
         throw std::runtime_error("2D histograms with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name, wName};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Histo2D, V1, V2, W>(userColumns, h);
   }

   template <typename V1, typename V2, typename W>
   RResultPtr<::TH2D> Histo2D(const TH2DModel &model)
   {
      return Histo2D<V1, V2, W>(model, "", "", "");
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a three-dimensional histogram (*lazy action*)
   /// \tparam V1 The type of the column used to fill the x axis of the histogram. Inferred if not present.
   /// \tparam V2 The type of the column used to fill the y axis of the histogram. Inferred if not present.
   /// \tparam V3 The type of the column used to fill the z axis of the histogram. Inferred if not present.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \param[in] v3Name The name of the column that will fill the z axis.
   /// \return the tridimensional histogram wrapped in a `RResultPtr`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo3D({"name", "title", 64u, 0., 128., 32u, -4., 4., 8u, -2., 2.},
   ///                             "myValueX", "myValueY", "myValueZ");
   /// // Explicit column types
   /// auto myHist2 = myDf.Histo3D<double, double, float>({"name", "title", 64u, 0., 128., 32u, -4., 4., 8u, -2., 2.},
   ///                                                    "myValueX", "myValueY", "myValueZ");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType,
             typename V3 = RDFDetail::RInferredType>
   RResultPtr<::TH3D> Histo3D(const TH3DModel &model, std::string_view v1Name = "", std::string_view v2Name = "",
                              std::string_view v3Name = "")
   {
      std::shared_ptr<::TH3D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetHistogram();
      }
      if (!RDFInternal::HistoUtils<::TH3D>::HasAxisLimits(*h)) {
         throw std::runtime_error("3D histograms with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name, v3Name};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Histo3D, V1, V2, V3>(userColumns, h);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a three-dimensional histogram (*lazy action*)
   /// \tparam V1 The type of the column used to fill the x axis of the histogram. Inferred if not present.
   /// \tparam V2 The type of the column used to fill the y axis of the histogram. Inferred if not present.
   /// \tparam V3 The type of the column used to fill the z axis of the histogram. Inferred if not present.
   /// \tparam W The type of the column used for the weights of the histogram. Inferred if not present.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \param[in] v3Name The name of the column that will fill the z axis.
   /// \param[in] wName The name of the column that will provide the weights.
   /// \return the tridimensional histogram wrapped in a `RResultPtr`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myHist1 = myDf.Histo3D({"name", "title", 64u, 0., 128., 32u, -4., 4., 8u, -2., 2.},
   ///                             "myValueX", "myValueY", "myValueZ", "myWeight");
   /// // Explicit column types
   /// using d_t = double;
   /// auto myHist2 = myDf.Histo3D<d_t, d_t, float, d_t>({"name", "title", 64u, 0., 128., 32u, -4., 4., 8u, -2., 2.},
   ///                                                    "myValueX", "myValueY", "myValueZ", "myWeight");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType,
             typename V3 = RDFDetail::RInferredType, typename W = RDFDetail::RInferredType>
   RResultPtr<::TH3D> Histo3D(const TH3DModel &model, std::string_view v1Name, std::string_view v2Name,
                              std::string_view v3Name, std::string_view wName)
   {
      std::shared_ptr<::TH3D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetHistogram();
      }
      if (!RDFInternal::HistoUtils<::TH3D>::HasAxisLimits(*h)) {
         throw std::runtime_error("3D histograms with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name, v3Name, wName};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Histo3D, V1, V2, V3, W>(userColumns, h);
   }

   template <typename V1, typename V2, typename V3, typename W>
   RResultPtr<::TH3D> Histo3D(const TH3DModel &model)
   {
      return Histo3D<V1, V2, V3, W>(model, "", "", "", "");
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a graph (*lazy action*)
   /// \tparam V1 The type of the column used to fill the x axis of the graph.
   /// \tparam V2 The type of the column used to fill the y axis of the graph.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \return the graph wrapped in a `RResultPtr`.
   ///
   /// Columns can be of a container type (e.g. std::vector<double>), in which case the graph
   /// is filled with each one of the elements of the container.
   /// If Multithreading is enabled, the order in which points are inserted is undefined.
   /// If the Graph has to be drawn, it is suggested to the user to sort it on the x before printing.
   /// A name and a title to the graph is given based on the input column names.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myGraph1 = myDf.Graph("xValues", "yValues");
   /// // Explicit column types
   /// auto myGraph2 = myDf.Graph<int, float>("xValues", "yValues");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType>
   RResultPtr<::TGraph> Graph(std::string_view v1Name = "", std::string_view v2Name = "")
   {
      auto graph = std::make_shared<::TGraph>();
      const std::vector<std::string_view> columnViews = {v1Name, v2Name};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());

      const auto validatedColumns = GetValidatedColumnNames(2, userColumns);

      // We build a default name and title based on the input columns
      if (!(validatedColumns[0].empty() && validatedColumns[1].empty())) {
         const auto g_name = std::string(v1Name) + "_vs_" + std::string(v2Name);
         const auto g_title = std::string(v1Name) + " vs " + std::string(v2Name);
         graph->SetNameTitle(g_name.c_str(), g_title.c_str());
         graph->GetXaxis()->SetTitle(std::string(v1Name).c_str());
         graph->GetYaxis()->SetTitle(std::string(v2Name).c_str());
      }

      return CreateAction<RDFInternal::ActionTags::Graph, V1, V2>(validatedColumns, graph);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a one-dimensional profile (*lazy action*)
   /// \tparam V1 The type of the column the values of which are used to fill the profile. Inferred if not present.
   /// \tparam V2 The type of the column the values of which are used to fill the profile. Inferred if not present.
   /// \param[in] model The model to be considered to build the new return value.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \return the monodimensional profile wrapped in a `RResultPtr`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myProf1 = myDf.Profile1D({"profName", "profTitle", 64u, -4., 4.}, "xValues", "yValues");
   /// // Explicit column types
   /// auto myProf2 = myDf.Graph<int, float>({"profName", "profTitle", 64u, -4., 4.}, "xValues", "yValues");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType>
   RResultPtr<::TProfile>
   Profile1D(const TProfile1DModel &model, std::string_view v1Name = "", std::string_view v2Name = "")
   {
      std::shared_ptr<::TProfile> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetProfile();
      }

      if (!RDFInternal::HistoUtils<::TProfile>::HasAxisLimits(*h)) {
         throw std::runtime_error("Profiles with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Profile1D, V1, V2>(userColumns, h);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a one-dimensional profile (*lazy action*)
   /// \tparam V1 The type of the column the values of which are used to fill the profile. Inferred if not present.
   /// \tparam V2 The type of the column the values of which are used to fill the profile. Inferred if not present.
   /// \tparam W The type of the column the weights of which are used to fill the profile. Inferred if not present.
   /// \param[in] model The model to be considered to build the new return value.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \param[in] wName The name of the column that will provide the weights.
   /// \return the monodimensional profile wrapped in a `RResultPtr`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myProf1 = myDf.Profile1D({"profName", "profTitle", 64u, -4., 4.}, "xValues", "yValues", "weight");
   /// // Explicit column types
   /// auto myProf2 = myDf.Profile1D<int, float, double>({"profName", "profTitle", 64u, -4., 4.},
   ///                                                   "xValues", "yValues", "weight");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType,
             typename W = RDFDetail::RInferredType>
   RResultPtr<::TProfile>
   Profile1D(const TProfile1DModel &model, std::string_view v1Name, std::string_view v2Name, std::string_view wName)
   {
      std::shared_ptr<::TProfile> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetProfile();
      }

      if (!RDFInternal::HistoUtils<::TProfile>::HasAxisLimits(*h)) {
         throw std::runtime_error("Profile histograms with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name, wName};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Profile1D, V1, V2, W>(userColumns, h);
   }

   template <typename V1, typename V2, typename W>
   RResultPtr<::TProfile> Profile1D(const TProfile1DModel &model)
   {
      return Profile1D<V1, V2, W>(model, "", "", "");
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a two-dimensional profile (*lazy action*)
   /// \tparam V1 The type of the column used to fill the x axis of the histogram. Inferred if not present.
   /// \tparam V2 The type of the column used to fill the y axis of the histogram. Inferred if not present.
   /// \tparam V2 The type of the column used to fill the z axis of the histogram. Inferred if not present.
   /// \param[in] model The returned profile will be constructed using this as a model.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \param[in] v3Name The name of the column that will fill the z axis.
   /// \return the bidimensional profile wrapped in a `RResultPtr`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myProf1 = myDf.Profile2D({"profName", "profTitle", 40, -4, 4, 40, -4, 4, 0, 20},
   ///                               "xValues", "yValues", "zValues");
   /// // Explicit column types
   /// auto myProf2 = myDf.Profile2D<int, float, double>({"profName", "profTitle", 40, -4, 4, 40, -4, 4, 0, 20},
   ///                                                   "xValues", "yValues", "zValues");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType,
             typename V3 = RDFDetail::RInferredType>
   RResultPtr<::TProfile2D> Profile2D(const TProfile2DModel &model, std::string_view v1Name = "",
                                      std::string_view v2Name = "", std::string_view v3Name = "")
   {
      std::shared_ptr<::TProfile2D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetProfile();
      }

      if (!RDFInternal::HistoUtils<::TProfile2D>::HasAxisLimits(*h)) {
         throw std::runtime_error("2D profiles with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name, v3Name};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Profile2D, V1, V2, V3>(userColumns, h);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Fill and return a two-dimensional profile (*lazy action*)
   /// \tparam V1 The type of the column used to fill the x axis of the histogram. Inferred if not present.
   /// \tparam V2 The type of the column used to fill the y axis of the histogram. Inferred if not present.
   /// \tparam V3 The type of the column used to fill the z axis of the histogram. Inferred if not present.
   /// \tparam W The type of the column used for the weights of the histogram. Inferred if not present.
   /// \param[in] model The returned histogram will be constructed using this as a model.
   /// \param[in] v1Name The name of the column that will fill the x axis.
   /// \param[in] v2Name The name of the column that will fill the y axis.
   /// \param[in] v3Name The name of the column that will fill the z axis.
   /// \param[in] wName The name of the column that will provide the weights.
   /// \return the bidimensional profile wrapped in a `RResultPtr`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto myProf1 = myDf.Profile2D({"profName", "profTitle", 40, -4, 4, 40, -4, 4, 0, 20},
   ///                               "xValues", "yValues", "zValues", "weight");
   /// // Explicit column types
   /// auto myProf2 = myDf.Profile2D<int, float, double, int>({"profName", "profTitle", 40, -4, 4, 40, -4, 4, 0, 20},
   ///                                                        "xValues", "yValues", "zValues", "weight");
   /// ~~~
   ///
   template <typename V1 = RDFDetail::RInferredType, typename V2 = RDFDetail::RInferredType,
             typename V3 = RDFDetail::RInferredType, typename W = RDFDetail::RInferredType>
   RResultPtr<::TProfile2D> Profile2D(const TProfile2DModel &model, std::string_view v1Name, std::string_view v2Name,
                                      std::string_view v3Name, std::string_view wName)
   {
      std::shared_ptr<::TProfile2D> h(nullptr);
      {
         ROOT::Internal::RDF::RIgnoreErrorLevelRAII iel(kError);
         h = model.GetProfile();
      }

      if (!RDFInternal::HistoUtils<::TProfile2D>::HasAxisLimits(*h)) {
         throw std::runtime_error("2D profiles with no axes limits are not supported yet.");
      }
      const std::vector<std::string_view> columnViews = {v1Name, v2Name, v3Name, wName};
      const auto userColumns = RDFInternal::AtLeastOneEmptyString(columnViews)
                                  ? ColumnNames_t()
                                  : ColumnNames_t(columnViews.begin(), columnViews.end());
      return CreateAction<RDFInternal::ActionTags::Profile2D, V1, V2, V3, W>(userColumns, h);
   }

   template <typename V1, typename V2, typename V3, typename W>
   RResultPtr<::TProfile2D> Profile2D(const TProfile2DModel &model)
   {
      return Profile2D<V1, V2, V3, W>(model, "", "", "", "");
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return an object of type T on which `T::Fill` will be called once per event (*lazy action*)
   ///
   /// T must be a type that provides a copy- or move-constructor and a `T::Fill` method that takes as many arguments
   /// as the column names pass as columnList. The arguments of `T::Fill` must have type equal to the one of the
   /// specified columns (these types are passed as template parameters to this method).
   /// \tparam FirstColumn The first type of the column the values of which are used to fill the object.
   /// \tparam OtherColumns A list of the other types of the columns the values of which are used to fill the object.
   /// \tparam T The type of the object to fill. Automatically deduced.
   /// \param[in] model The model to be considered to build the new return value.
   /// \param[in] columnList A list containing the names of the columns that will be passed when calling `Fill`
   /// \return the filled object wrapped in a `RResultPtr`.
   ///
   /// The user gives up ownership of the model object.
   /// The list of column names to be used for filling must always be specified.
   /// This action is *lazy*: upon invocation of this method the calculation is booked but not executed.
   /// See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// MyClass obj;
   /// auto myFilledObj = myDf.Fill<float>(obj, {"col0", "col1"});
   /// ~~~
   ///
   template <typename FirstColumn, typename... OtherColumns, typename T> // need FirstColumn to disambiguate overloads
   RResultPtr<T> Fill(T &&model, const ColumnNames_t &columnList)
   {
      auto h = std::make_shared<T>(std::forward<T>(model));
      if (!RDFInternal::HistoUtils<T>::HasAxisLimits(*h)) {
         throw std::runtime_error("The absence of axes limits is not supported yet.");
      }
      return CreateAction<RDFInternal::ActionTags::Fill, FirstColumn, OtherColumns...>(columnList, h);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return an object of type T on which `T::Fill` will be called once per event (*lazy action*)
   ///
   /// This overload infers the types of the columns specified in columnList at runtime and just-in-time compiles the
   /// method with these types. See previous overload for more information.
   /// \tparam T The type of the object to fill. Automatically deduced.
   /// \param[in] model The model to be considered to build the new return value.
   /// \param[in] columnList The name of the columns read to fill the object.
   /// \return the filled object wrapped in a `RResultPtr`.
   ///
   /// This overload of `Fill` infers the type of the specified columns at runtime and just-in-time compiles the
   /// previous overload. Check the previous overload for more details on `Fill`.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// MyClass obj;
   /// auto myFilledObj = myDf.Fill(obj, {"col0", "col1"});
   /// ~~~
   ///
   template <typename T>
   RResultPtr<T> Fill(T &&model, const ColumnNames_t &bl)
   {
      auto h = std::make_shared<T>(std::forward<T>(model));
      if (!RDFInternal::HistoUtils<T>::HasAxisLimits(*h)) {
         throw std::runtime_error("The absence of axes limits is not supported yet.");
      }
      return CreateAction<RDFInternal::ActionTags::Fill, RDFDetail::RInferredType>(bl, h, bl.size());
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return a TStatistic object, filled once per event (*lazy action*)
   ///
   /// \tparam V The type of the value column
   /// \param[in] value The name of the column with the values to fill the statistics with.
   /// \return the filled TStatistic object wrapped in a `RResultPtr`.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto stats0 = myDf.Stats("values");
   /// // Explicit column type
   /// auto stats1 = myDf.Stats<float>("values");
   /// ~~~
   ///
   template<typename V = RDFDetail::RInferredType>
   RResultPtr<TStatistic> Stats(std::string_view value = "")
   {
      ColumnNames_t columns;
      if (!value.empty()) {
         columns.emplace_back(std::string(value));
      }
      const auto validColumnNames = GetValidatedColumnNames(1, columns);
      if (std::is_same<V, RDFDetail::RInferredType>::value) {
         return Fill(TStatistic(), validColumnNames);
      }
      else {
         return Fill<V>(TStatistic(), validColumnNames);
      }
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return a TStatistic object, filled once per event (*lazy action*)
   ///
   /// \tparam V The type of the value column
   /// \tparam W The type of the weight column
   /// \param[in] value The name of the column with the values to fill the statistics with.
   /// \param[in] weight The name of the column with the weights to fill the statistics with.
   /// \return the filled TStatistic object wrapped in a `RResultPtr`.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column types (this invocation needs jitting internally)
   /// auto stats0 = myDf.Stats("values", "weights");
   /// // Explicit column types
   /// auto stats1 = myDf.Stats<int, float>("values", "weights");
   /// ~~~
   ///
   template<typename V = RDFDetail::RInferredType, typename W = RDFDetail::RInferredType>
   RResultPtr<TStatistic> Stats(std::string_view value, std::string_view weight)
   {
      ColumnNames_t columns {std::string(value), std::string(weight)};
      constexpr auto vIsInferred = std::is_same<V, RDFDetail::RInferredType>::value;
      constexpr auto wIsInferred = std::is_same<W, RDFDetail::RInferredType>::value;
      const auto validColumnNames = GetValidatedColumnNames(2, columns);
      // We have 3 cases: 
      // 1. Both types are inferred: we use Fill and let the jit kick in.
      // 2. One of the two types is explicit and the other one is inferred: the case is not supported.
      // 3. Both types are explicit: we invoke the fully compiled Fill method.
      if (vIsInferred && wIsInferred) {
         return Fill(TStatistic(), validColumnNames);
      } else if (vIsInferred != wIsInferred) {
         std::string error("The ");
         error += vIsInferred ? "value " : "weight ";
         error += "column type is explicit, while the ";
         error += vIsInferred ? "weight " : "value ";
         error += " is specified to be inferred. This case is not supported: please specify both types or none.";
         throw std::runtime_error(error);
      } else {
         return Fill<V, W>(TStatistic(), validColumnNames);
      }
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return the minimum of processed column values (*lazy action*)
   /// \tparam T The type of the branch/column.
   /// \param[in] columnName The name of the branch/column to be treated.
   /// \return the minimum value of the selected column wrapped in a `RResultPtr`.
   ///
   /// If T is not specified, RDataFrame will infer it from the data and just-in-time compile the correct
   /// template specialization of this method.
   /// If the type of the column is inferred, the return type is `double`, the type of the column otherwise.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto minVal0 = myDf.Min("values");
   /// // Explicit column type
   /// auto minVal1 = myDf.Min<double>("values");
   /// ~~~
   ///
   template <typename T = RDFDetail::RInferredType>
   RResultPtr<RDFDetail::MinReturnType_t<T>> Min(std::string_view columnName = "")
   {
      const auto userColumns = columnName.empty() ? ColumnNames_t() : ColumnNames_t({std::string(columnName)});
      using RetType_t = RDFDetail::MinReturnType_t<T>;
      auto minV = std::make_shared<RetType_t>(std::numeric_limits<RetType_t>::max());
      return CreateAction<RDFInternal::ActionTags::Min, T>(userColumns, minV);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return the maximum of processed column values (*lazy action*)
   /// \tparam T The type of the branch/column.
   /// \param[in] columnName The name of the branch/column to be treated.
   /// \return the maximum value of the selected column wrapped in a `RResultPtr`.
   ///
   /// If T is not specified, RDataFrame will infer it from the data and just-in-time compile the correct
   /// template specialization of this method.
   /// If the type of the column is inferred, the return type is `double`, the type of the column otherwise.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto maxVal0 = myDf.Max("values");
   /// // Explicit column type
   /// auto maxVal1 = myDf.Max<double>("values");
   /// ~~~
   ///
   template <typename T = RDFDetail::RInferredType>
   RResultPtr<RDFDetail::MaxReturnType_t<T>> Max(std::string_view columnName = "")
   {
      const auto userColumns = columnName.empty() ? ColumnNames_t() : ColumnNames_t({std::string(columnName)});
      using RetType_t = RDFDetail::MaxReturnType_t<T>;
      auto maxV = std::make_shared<RetType_t>(std::numeric_limits<RetType_t>::lowest());
      return CreateAction<RDFInternal::ActionTags::Max, T>(userColumns, maxV);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return the mean of processed column values (*lazy action*)
   /// \tparam T The type of the branch/column.
   /// \param[in] columnName The name of the branch/column to be treated.
   /// \return the mean value of the selected column wrapped in a `RResultPtr`.
   ///
   /// If T is not specified, RDataFrame will infer it from the data and just-in-time compile the correct
   /// template specialization of this method.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto meanVal0 = myDf.Mean("values");
   /// // Explicit column type
   /// auto meanVal1 = myDf.Mean<double>("values");
   /// ~~~
   ///
   template <typename T = RDFDetail::RInferredType>
   RResultPtr<double> Mean(std::string_view columnName = "")
   {
      const auto userColumns = columnName.empty() ? ColumnNames_t() : ColumnNames_t({std::string(columnName)});
      auto meanV = std::make_shared<double>(0);
      return CreateAction<RDFInternal::ActionTags::Mean, T>(userColumns, meanV);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return the unbiased standard deviation of processed column values (*lazy action*)
   /// \tparam T The type of the branch/column.
   /// \param[in] columnName The name of the branch/column to be treated.
   /// \return the standard deviation value of the selected column wrapped in a `RResultPtr`.
   ///
   /// If T is not specified, RDataFrame will infer it from the data and just-in-time compile the correct
   /// template specialization of this method.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto stdDev0 = myDf.StdDev("values");
   /// // Explicit column type
   /// auto stdDev1 = myDf.StdDev<double>("values");
   /// ~~~
   ///
   template <typename T = RDFDetail::RInferredType>
   RResultPtr<double> StdDev(std::string_view columnName = "")
   {
      const auto userColumns = columnName.empty() ? ColumnNames_t() : ColumnNames_t({std::string(columnName)});
      auto stdDeviationV = std::make_shared<double>(0);
      return CreateAction<RDFInternal::ActionTags::StdDev, T>(userColumns, stdDeviationV);
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Return the sum of processed column values (*lazy action*)
   /// \tparam T The type of the branch/column.
   /// \param[in] columnName The name of the branch/column.
   /// \param[in] initValue Optional initial value for the sum. If not present, the column values must be default-constructible.
   /// \return the sum of the selected column wrapped in a `RResultPtr`.
   ///
   /// If T is not specified, RDataFrame will infer it from the data and just-in-time compile the correct
   /// template specialization of this method.
   /// If the type of the column is inferred, the return type is `double`, the type of the column otherwise.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is
   /// booked but not executed. See RResultPtr documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// // Deduce column type (this invocation needs jitting internally)
   /// auto sum0 = myDf.Sum("values");
   /// // Explicit column type
   /// auto sum1 = myDf.Sum<double>("values");
   /// ~~~
   ///
   template <typename T = RDFDetail::RInferredType>
   RResultPtr<RDFDetail::SumReturnType_t<T>>
   Sum(std::string_view columnName = "",
       const RDFDetail::SumReturnType_t<T> &initValue = RDFDetail::SumReturnType_t<T>{})
   {
      const auto userColumns = columnName.empty() ? ColumnNames_t() : ColumnNames_t({std::string(columnName)});
      auto sumV = std::make_shared<RDFDetail::SumReturnType_t<T>>(initValue);
      return CreateAction<RDFInternal::ActionTags::Sum, T>(userColumns, sumV);
   }
   // clang-format on

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Gather filtering statistics
   /// \return the resulting `RCutFlowReport` instance wrapped in a `RResultPtr`.
   ///
   /// Calling `Report` on the main `RDataFrame` object gathers stats for
   /// all named filters in the call graph. Calling this method on a
   /// stored chain state (i.e. a graph node different from the first) gathers
   /// the stats for all named filters in the chain section between the original
   /// `RDataFrame` and that node (included). Stats are gathered in the same
   /// order as the named filters have been added to the graph.
   /// A RResultPtr<RCutFlowReport> is returned to allow inspection of the
   /// effects cuts had.
   ///
   /// This action is *lazy*: upon invocation of
   /// this method the calculation is booked but not executed. See RResultPtr
   /// documentation.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto filtered = d.Filter(cut1, {"b1"}, "Cut1").Filter(cut2, {"b2"}, "Cut2");
   /// auto cutReport = filtered3.Report();
   /// cutReport->Print();
   /// ~~~
   ///
   RResultPtr<RCutFlowReport> Report()
   {
      bool returnEmptyReport = false;
      // if this is a RInterface<RLoopManager> on which `Define` has been called, users
      // are calling `Report` on a chain of the form LoopManager->Define->Define->..., which
      // certainly does not contain named filters.
      // The number 4 takes into account the implicit columns for entry and slot number
      // and their aliases (2 + 2, i.e. {r,t}dfentry_ and {r,t}dfslot_)
      if (std::is_same<Proxied, RLoopManager>::value && fCustomColumns.GetNames().size() > 4)
         returnEmptyReport = true;

      auto rep = std::make_shared<RCutFlowReport>();
      using Helper_t = RDFInternal::ReportHelper<Proxied>;
      using Action_t = RDFInternal::RAction<Helper_t, Proxied>;

      auto action = std::make_unique<Action_t>(Helper_t(rep, fProxiedPtr, returnEmptyReport), ColumnNames_t({}),
                                               fProxiedPtr, RDFInternal::RBookedCustomColumns(fCustomColumns));

      fLoopManager->Book(action.get());
      return MakeResultPtr(rep, *fLoopManager, std::move(action));
   }

   /////////////////////////////////////////////////////////////////////////////
   /// \brief Returns the names of the available columns
   /// \return the container of column names.
   ///
   /// This is not an action nor a transformation, just a query to the RDataFrame object.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto colNames = d.GetColumnNames();
   /// // Print columns' names
   /// for (auto &&colName : colNames) std::cout << colName << std::endl;
   /// ~~~
   ///
   ColumnNames_t GetColumnNames()
   {
      ColumnNames_t allColumns;

      auto addIfNotInternal = [&allColumns](std::string_view colName) {
         if (!RDFInternal::IsInternalColumn(colName))
            allColumns.emplace_back(colName);
      };

      auto columnNames = fCustomColumns.GetNames();

      std::for_each(columnNames.begin(), columnNames.end(), addIfNotInternal);

      auto tree = fLoopManager->GetTree();
      if (tree) {
         auto branchNames = RDFInternal::GetBranchNames(*tree, /*allowDuplicates=*/false);
         allColumns.insert(allColumns.end(), branchNames.begin(), branchNames.end());
      }

      if (fDataSource) {
         auto &dsColNames = fDataSource->GetColumnNames();
         allColumns.insert(allColumns.end(), dsColNames.begin(), dsColNames.end());
      }

      return allColumns;
   }

   /////////////////////////////////////////////////////////////////////////////
   /// \brief Return the type of a given column as a string.
   /// \return the type of the required column.
   ///
   /// This is not an action nor a transformation, just a query to the RDataFrame object.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto colType = d.GetColumnType("columnName");
   /// // Print column type
   /// std::cout << "Column " << colType << " has type " << colType << std::endl;
   /// ~~~
   ///
   std::string GetColumnType(std::string_view column)
   {
      const auto &customCols = fCustomColumns.GetNames();
      const bool convertVector2RVec = true;
      const auto isCustom = std::find(customCols.begin(), customCols.end(), column) != customCols.end();
      if (!isCustom) {
         return RDFInternal::ColumnName2ColumnTypeName(std::string(column), fLoopManager->GetID(),
                                                       fLoopManager->GetTree(), fLoopManager->GetDataSource(), isCustom,
                                                       convertVector2RVec);
      } else {
         // must convert the alias "__rdf::column_type" to a readable type
         const auto colID = std::to_string(fCustomColumns.GetColumns().at(std::string(column))->GetID());
         const auto call = "ROOT::Internal::RDF::TypeID2TypeName(typeid(__rdf" + std::to_string(fLoopManager->GetID()) +
                           "::" + std::string(column) + colID + "_type))";
         fLoopManager->JitDeclarations(); // some type aliases might be needed by the code jitted in the next line
         const auto calcRes = RDFInternal::InterpreterCalc(call);
         return *reinterpret_cast<std::string *>(calcRes); // copy result to stack
      }
   }

   /// \brief Returns the names of the filters created.
   /// \return the container of filters names.
   ///
   /// If called on a root node, all the filters in the computation graph will
   /// be printed. For any other node, only the filters upstream of that node.
   /// Filters without a name are printed as "Unnamed Filter"
   /// This is not an action nor a transformation, just a query to the RDataFrame object.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto filtNames = d.GetFilterNames();
   /// for (auto &&filtName : filtNames) std::cout << filtName << std::endl;
   /// ~~~
   ///
   std::vector<std::string> GetFilterNames() { return RDFInternal::GetFilterNames(fProxiedPtr); }

   /// \brief Returns the names of the defined columns
   /// \return the container of the defined column names.
   ///
   /// This is not an action nor a transformation, just a simple utility to
   /// get the columns names that have been defined up to the node.
   /// If no custom column has been defined, e.g. on a root node, it returns an
   /// empty collection.
   ///
   /// ### Example usage:
   /// ~~~{.cpp}
   /// auto defColNames = d.GetDefinedColumnNames();
   /// // Print defined columns' names
   /// for (auto &&defColName : defColNames) std::cout << defColName << std::endl;
   /// ~~~
   ///
   ColumnNames_t GetDefinedColumnNames()
   {
      ColumnNames_t definedColumns;

      auto columns = fCustomColumns.GetColumns();

      for (auto column : columns) {
         if (!RDFInternal::IsInternalColumn(column.first) && !column.second->IsDataSourceColumn())
            definedColumns.emplace_back(column.first);
      }

      return definedColumns;
   }

   /// \brief Checks if a column is present in the dataset
   /// \return true if the column is available, false otherwise
   ///
   /// This method checks if a column is part of the input ROOT dataset, has
   /// been defined or can be provided by the data source.
   ///
   /// Example usage:
   /// ~~~{.cpp}
   /// ROOT::RDataFrame base(1);
   /// auto rdf = base.Define("definedColumn", [](){return 0;});
   /// rdf.HasColumn("definedColumn"); // true: we defined it
   /// rdf.HasColumn("rdfentry_"); // true: it's always there
   /// rdf.HasColumn("foo"); // false: it is not there
   /// ~~~
   bool HasColumn(std::string_view columnName)
   {
      if (fCustomColumns.HasName(columnName))
         return true;

      if (auto tree = fLoopManager->GetTree()) {
         const auto &branchNames = fLoopManager->GetBranchNames();
         const auto branchNamesEnd = branchNames.end();
         if (branchNamesEnd != std::find(branchNames.begin(), branchNamesEnd, columnName))
            return true;
      }

      if (fDataSource && fDataSource->HasColumn(columnName))
         return true;

      return false;
   }

   /// \brief Gets the number of data processing slots
   /// \return The number of data processing slots used by this RDataFrame instance
   ///
   /// This method returns the number of data processing slots used by this RDataFrame
   /// instance. This number is influenced by the global switch ROOT::EnableImplicitMT().
   ///
   /// Example usage:
   /// ~~~{.cpp}
   /// ROOT::EnableImplicitMT(6)
   /// ROOT::RDataFrame df(1);
   /// std::cout << df.GetNSlots() << std::endl; // prints "6"
   /// ~~~
   unsigned int GetNSlots() const { return fLoopManager->GetNSlots(); }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Execute a user-defined accumulation operation on the processed column values in each processing slot
   /// \tparam F The type of the aggregator callable. Automatically deduced.
   /// \tparam U The type of the aggregator variable. Must be default-constructible, copy-constructible and copy-assignable. Automatically deduced.
   /// \tparam T The type of the column to apply the reduction to. Automatically deduced.
   /// \param[in] aggregator A callable with signature `U(U,T)` or `void(U&,T)`, where T is the type of the column, U is the type of the aggregator variable
   /// \param[in] merger A callable with signature `U(U,U)` or `void(std::vector<U>&)` used to merge the results of the accumulations of each thread
   /// \param[in] columnName The column to be aggregated. If omitted, the first default column is used instead.
   /// \param[in] aggIdentity The aggregator variable of each thread is initialised to this value (or is default-constructed if the parameter is omitted)
   /// \return the result of the aggregation wrapped in a `RResultPtr`.
   ///
   /// An aggregator callable takes two values, an aggregator variable and a column value. The aggregator variable is
   /// initialized to aggIdentity or default-constructed if aggIdentity is omitted.
   /// This action calls the aggregator callable for each processed entry, passing in the aggregator variable and
   /// the value of the column columnName.
   /// If the signature is `U(U,T)` the aggregator variable is then copy-assigned the result of the execution of the callable.
   /// Otherwise the signature of aggregator must be `void(U&,T)`.
   ///
   /// The merger callable is used to merge the partial accumulation results of each processing thread. It is only called in multi-thread executions.
   /// If its signature is `U(U,U)` the aggregator variables of each thread are merged two by two.
   /// If its signature is `void(std::vector<U>& a)` it is assumed that it merges all aggregators in a[0].
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is booked but not executed. See RResultPtr documentation.
   ///
   /// Example usage:
   /// ~~~{.cpp}
   /// auto aggregator = [](double acc, double x) { return acc * x; };
   /// ROOT::EnableImplicitMT();
   /// // If multithread is enabled, the aggregator function will be called by more threads
   /// // and will produce a vector of partial accumulators.
   /// // The merger function performs the final aggregation of these partial results.
   /// auto merger = [](std::vector<double> &accumulators) {
   ///    for (auto i : ROOT::TSeqU(1u, accumulators.size())) {
   ///       accumulators[0] *= accumulators[i];
   ///    }
   /// };
   ///
   /// // The accumulator is initialized at this value by every thread.
   /// double initValue = 1.;
   ///
   /// // Multiplies all elements of the column "x"
   /// auto result = d.Aggregate(aggregator, merger, columnName, initValue);
   /// ~~~
   // clang-format on
   template <typename AccFun, typename MergeFun, typename R = typename TTraits::CallableTraits<AccFun>::ret_type,
             typename ArgTypes = typename TTraits::CallableTraits<AccFun>::arg_types,
             typename ArgTypesNoDecay = typename TTraits::CallableTraits<AccFun>::arg_types_nodecay,
             typename U = TTraits::TakeFirstParameter_t<ArgTypes>,
             typename T = TTraits::TakeFirstParameter_t<TTraits::RemoveFirstParameter_t<ArgTypes>>>
   RResultPtr<U> Aggregate(AccFun aggregator, MergeFun merger, std::string_view columnName, const U &aggIdentity)
   {
      RDFInternal::CheckAggregate<R, MergeFun>(ArgTypesNoDecay());
      const auto columns = columnName.empty() ? ColumnNames_t() : ColumnNames_t({std::string(columnName)});
      constexpr auto nColumns = ArgTypes::list_size;

      const auto validColumnNames = GetValidatedColumnNames(1, columns);

      auto newColumns = CheckAndFillDSColumns(validColumnNames, std::make_index_sequence<nColumns>(), ArgTypes());

      auto accObjPtr = std::make_shared<U>(aggIdentity);
      using Helper_t = RDFInternal::AggregateHelper<AccFun, MergeFun, R, T, U>;
      using Action_t = typename RDFInternal::RAction<Helper_t, Proxied>;
      auto action = std::make_unique<Action_t>(
         Helper_t(std::move(aggregator), std::move(merger), accObjPtr, fLoopManager->GetNSlots()), validColumnNames,
         fProxiedPtr, std::move(newColumns));
      fLoopManager->Book(action.get());
      return MakeResultPtr(accObjPtr, *fLoopManager, std::move(action));
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Execute a user-defined accumulation operation on the processed column values in each processing slot
   /// \tparam F The type of the aggregator callable. Automatically deduced.
   /// \tparam U The type of the aggregator variable. Must be default-constructible, copy-constructible and copy-assignable. Automatically deduced.
   /// \tparam T The type of the column to apply the reduction to. Automatically deduced.
   /// \param[in] aggregator A callable with signature `U(U,T)` or `void(U,T)`, where T is the type of the column, U is the type of the aggregator variable
   /// \param[in] merger A callable with signature `U(U,U)` or `void(std::vector<U>&)` used to merge the results of the accumulations of each thread
   /// \param[in] columnName The column to be aggregated. If omitted, the first default column is used instead.
   /// \return the result of the aggregation wrapped in a `RResultPtr`.
   ///
   /// See previous Aggregate overload for more information.
   // clang-format on
   template <typename AccFun, typename MergeFun, typename R = typename TTraits::CallableTraits<AccFun>::ret_type,
             typename ArgTypes = typename TTraits::CallableTraits<AccFun>::arg_types,
             typename U = TTraits::TakeFirstParameter_t<ArgTypes>,
             typename T = TTraits::TakeFirstParameter_t<TTraits::RemoveFirstParameter_t<ArgTypes>>>
   RResultPtr<U> Aggregate(AccFun aggregator, MergeFun merger, std::string_view columnName = "")
   {
      static_assert(
         std::is_default_constructible<U>::value,
         "aggregated object cannot be default-constructed. Please provide an initialisation value (aggIdentity)");
      return Aggregate(std::move(aggregator), std::move(merger), columnName, U());
   }

   // clang-format off
   ////////////////////////////////////////////////////////////////////////////
   /// \brief Book execution of a custom action using a user-defined helper object.
   /// \tparam ColumnTypes List of types of columns used by this action.
   /// \tparam Helper The type of the user-defined helper. See below for the required interface it should expose.
   /// \param[in] helper The Action Helper to be scheduled.
   /// \param[in] columns The names of the columns on which the helper acts.
   /// \return the result of the helper wrapped in a `RResultPtr`.
   ///
   /// This method books a custom action for execution. The behavior of the action is completely dependent on the
   /// Helper object provided by the caller. The minimum required interface for the helper is the following (more
   /// methods can be present, e.g. a constructor that takes the number of worker threads is usually useful):
   ///
   /// * Helper must publicly inherit from ROOT::Detail::RDF::RActionImpl<Helper>
   /// * Helper(Helper &&): a move-constructor is required. Copy-constructors are discouraged.
   /// * Result_t: alias for the type of the result of this action helper. Must be default-constructible.
   /// * void Exec(unsigned int slot, ColumnTypes...columnValues): each working thread shall call this method
   ///   during the event-loop, possibly concurrently. No two threads will ever call Exec with the same 'slot' value:
   ///   this parameter is there to facilitate writing thread-safe helpers. The other arguments will be the values of
   ///   the requested columns for the particular entry being processed.
   /// * void InitTask(TTreeReader *, unsigned int slot): each working thread shall call this method during the event
   ///   loop, before processing a batch of entries (possibly read from the TTreeReader passed as argument, if not null).
   ///   This method can be used e.g. to prepare the helper to process a batch of entries in a given thread. Can be no-op.
   /// * void Initialize(): this method is called once before starting the event-loop. Useful for setup operations. Can be no-op.
   /// * void Finalize(): this method is called at the end of the event loop. Commonly used to finalize the contents of the result.
   /// * Result_t &PartialUpdate(unsigned int slot): this method is optional, i.e. can be omitted. If present, it should
   ///   return the value of the partial result of this action for the given 'slot'. Different threads might call this
   ///   method concurrently, but will always pass different 'slot' numbers.
   /// * std::shared_ptr<Result_t> GetResultPtr() const: return a shared_ptr to the result of this action (of type
   ///   Result_t). The RResultPtr returned by Book will point to this object.
   ///
   /// See ActionHelpers.hxx for the helpers used by standard RDF actions.
   /// This action is *lazy*: upon invocation of this method the calculation is booked but not executed. See RResultPtr documentation.
   // clang-format on
   template <typename... ColumnTypes, typename Helper>
   RResultPtr<typename Helper::Result_t> Book(Helper &&helper, const ColumnNames_t &columns = {})
   {
      constexpr auto nColumns = sizeof...(ColumnTypes);
      RDFInternal::CheckTypesAndPars(sizeof...(ColumnTypes), columns.size());

      const auto validColumnNames = GetValidatedColumnNames(nColumns, columns);

      // TODO add more static sanity checks on Helper
      using AH = RDFDetail::RActionImpl<Helper>;
      static_assert(std::is_base_of<AH, Helper>::value && std::is_convertible<Helper *, AH *>::value,
                    "Action helper of type T must publicly inherit from ROOT::Detail::RDF::RActionImpl<T>");

      using Action_t = typename RDFInternal::RAction<Helper, Proxied, TTraits::TypeList<ColumnTypes...>>;
      auto resPtr = helper.GetResultPtr();

      auto newColumns = CheckAndFillDSColumns(validColumnNames, std::make_index_sequence<nColumns>(),
                                              RDFInternal::TypeList<ColumnTypes...>());

      auto action = std::make_unique<Action_t>(Helper(std::forward<Helper>(helper)), validColumnNames, fProxiedPtr,
                                               RDFInternal::RBookedCustomColumns(newColumns));
      fLoopManager->Book(action.get());
      return MakeResultPtr(resPtr, *fLoopManager, std::move(action));
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Provides a representation of the columns in the dataset
   /// \tparam ColumnTypes variadic list of branch/column types.
   /// \param[in] columnList Names of the columns to be displayed.
   /// \param[in] rows Number of events for each column to be displayed.
   /// \return the `RDisplay` instance wrapped in a `RResultPtr`.
   ///
   /// This function returns a `RResultPtr<RDisplay>` containing all the entries to be displayed, organized in a tabular
   /// form. RDisplay will either print on the standard output a summarized version through `Print()` or will return a
   /// complete version through `AsString()`.
   ///
   /// This action is *lazy*: upon invocation of this method the calculation is booked but not executed. See RResultPtr documentation.
   ///
   /// Example usage:
   /// ~~~{.cpp}
   /// // Preparing the RResultPtr<RDisplay> object with all columns and default number of entries
   /// auto d1 = rdf.Display("");
   /// // Preparing the RResultPtr<RDisplay> object with two columns and 128 entries
   /// auto d2 = d.Display({"x", "y"}, 128);
   /// // Printing the short representations, the event loop will run
   /// d1->Print();
   /// d2->Print();
   /// ~~~
   template <typename... ColumnTypes>
   RResultPtr<RDisplay> Display(const ColumnNames_t &columnList, const int &nRows = 5)
   {
      CheckIMTDisabled("Display");

      auto displayer = std::make_shared<RDFInternal::RDisplay>(columnList, GetColumnTypeNamesList(columnList), nRows);
      return CreateAction<RDFInternal::ActionTags::Display, ColumnTypes...>(columnList, displayer);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Provides a representation of the columns in the dataset
   /// \param[in] columnList Names of the columns to be displayed.
   /// \param[in] rows Number of events for each column to be displayed.
   /// \return the `RDisplay` instance wrapped in a `RResultPtr`.
   ///
   /// This overload automatically infers the column types.
   /// See the previous overloads for further details.
   RResultPtr<RDisplay> Display(const ColumnNames_t &columnList, const int &nRows = 5)
   {
      CheckIMTDisabled("Display");
      auto displayer = std::make_shared<RDFInternal::RDisplay>(columnList, GetColumnTypeNamesList(columnList), nRows);
      return CreateAction<RDFInternal::ActionTags::Display, RDFDetail::RInferredType>(columnList, displayer,
                                                                                      columnList.size());
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Provides a representation of the columns in the dataset
   /// \param[in] columnNameRegexp A regular expression to select the columns.
   /// \param[in] rows Number of events for each column to be displayed.
   /// \return the `RDisplay` instance wrapped in a `RResultPtr`.
   ///
   /// The existing columns are matched against the regular expression. If the string provided
   /// is empty, all columns are selected.
   /// See the previous overloads for further details.
   RResultPtr<RDisplay> Display(std::string_view columnNameRegexp = "", const int &nRows = 5)
   {
      auto selectedColumns = RDFInternal::ConvertRegexToColumns(fCustomColumns, fLoopManager->GetTree(), fDataSource,
                                                                columnNameRegexp, "Display");
      return Display(selectedColumns, nRows);
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Provides a representation of the columns in the dataset
   /// \param[in] columnList Names of the columns to be displayed.
   /// \param[in] nRows Number of events for each column to be displayed.
   /// \return the `RDisplay` instance wrapped in a `RResultPtr`.
   ///
   /// See the previous overloads for further details.
   RResultPtr<RDisplay> Display(std::initializer_list<std::string> columnList, const int &nRows = 5)
   {
      ColumnNames_t selectedColumns(columnList);
      return Display(selectedColumns, nRows);
   }

private:
   void AddDefaultColumns()
   {
      RDFInternal::RBookedCustomColumns newCols;

      // Entry number column
      const auto entryColName = "rdfentry_";
      auto entryColGen = [](unsigned int, ULong64_t entry) { return entry; };
      using NewColEntry_t =
         RDFDetail::RCustomColumn<decltype(entryColGen), RDFDetail::CustomColExtraArgs::SlotAndEntry>;

      auto entryColumn = std::make_shared<NewColEntry_t>(fLoopManager, entryColName, std::move(entryColGen),
                                                         ColumnNames_t{}, fLoopManager->GetNSlots(), newCols);
      newCols.AddName(entryColName);
      newCols.AddColumn(entryColumn, entryColName);

      fLoopManager->RegisterCustomColumn(entryColumn.get());

      // Declare return type to the interpreter, for future use by jitted actions
      auto retTypeDeclaration = "namespace __rdf" + std::to_string(fLoopManager->GetID()) + " { using " + entryColName +
                                std::to_string(entryColumn->GetID()) + "_type = ULong64_t; }";
      fLoopManager->ToJitDeclare(retTypeDeclaration);

      // Slot number column
      const auto slotColName = "rdfslot_";
      auto slotColGen = [](unsigned int slot) { return slot; };
      using NewColSlot_t = RDFDetail::RCustomColumn<decltype(slotColGen), RDFDetail::CustomColExtraArgs::Slot>;

      auto slotColumn = std::make_shared<NewColSlot_t>(fLoopManager, slotColName, std::move(slotColGen),
                                                       ColumnNames_t{}, fLoopManager->GetNSlots(), newCols);

      newCols.AddName(slotColName);
      newCols.AddColumn(slotColumn, slotColName);

      fLoopManager->RegisterCustomColumn(slotColumn.get());

      fCustomColumns = std::move(newCols);

      // Declare return type to the interpreter, for future use by jitted actions
      retTypeDeclaration = "namespace __rdf" + std::to_string(fLoopManager->GetID()) + " { using " + slotColName +
                           std::to_string(slotColumn->GetID()) + "_type = unsigned int; }";
      fLoopManager->ToJitDeclare(retTypeDeclaration);

      fLoopManager->AddColumnAlias("tdfentry_", entryColName);
      fCustomColumns.AddName("tdfentry_");
      fLoopManager->AddColumnAlias("tdfslot_", slotColName);
      fCustomColumns.AddName("tdfslot_");
   }

   std::vector<std::string> GetColumnTypeNamesList(const ColumnNames_t &columnList)
   {
      std::vector<std::string> types;

      for (auto column : columnList) {
         types.push_back(GetColumnType(column));
      }
      return types;
   }

   void CheckIMTDisabled(std::string_view callerName)
   {
      if (ROOT::IsImplicitMTEnabled()) {
         std::string error(callerName);
         error += " was called with ImplicitMT enabled, but multi-thread is not supported.";
         throw std::runtime_error(error);
      }
   }

   // Type was specified by the user, no need to infer it
   template <typename ActionTag, typename... BranchTypes, typename ActionResultType,
             typename std::enable_if<!RDFInternal::TNeedJitting<BranchTypes...>::value, int>::type = 0>
   RResultPtr<ActionResultType> CreateAction(const ColumnNames_t &columns, const std::shared_ptr<ActionResultType> &r)
   {
      constexpr auto nColumns = sizeof...(BranchTypes);

      const auto validColumnNames = GetValidatedColumnNames(nColumns, columns);

      auto newColumns = CheckAndFillDSColumns(validColumnNames, std::make_index_sequence<nColumns>(),
                                              RDFInternal::TypeList<BranchTypes...>());

      const auto nSlots = fLoopManager->GetNSlots();

      auto action = RDFInternal::BuildAction<BranchTypes...>(validColumnNames, r, nSlots, fProxiedPtr, ActionTag{},
                                                             std::move(newColumns));
      fLoopManager->Book(action.get());
      return MakeResultPtr(r, *fLoopManager, std::move(action));
   }

   // User did not specify type, do type inference
   // This version of CreateAction has a `nColumns` optional argument. If present, the number of required columns for
   // this action is taken equal to nColumns, otherwise it is assumed to be sizeof...(BranchTypes)
   template <typename ActionTag, typename... BranchTypes, typename ActionResultType,
             typename std::enable_if<RDFInternal::TNeedJitting<BranchTypes...>::value, int>::type = 0>
   RResultPtr<ActionResultType>
   CreateAction(const ColumnNames_t &columns, const std::shared_ptr<ActionResultType> &r, const int nColumns = -1)
   {
      auto realNColumns = (nColumns > -1 ? nColumns : sizeof...(BranchTypes));

      const auto validColumnNames = GetValidatedColumnNames(realNColumns, columns);
      const unsigned int nSlots = fLoopManager->GetNSlots();

      auto tree = fLoopManager->GetTree();
      auto rOnHeap = RDFInternal::MakeSharedOnHeap(r);

      auto upcastNodeOnHeap = RDFInternal::MakeSharedOnHeap(RDFInternal::UpcastNode(fProxiedPtr));
      using BaseNodeType_t = typename std::remove_pointer<decltype(upcastNodeOnHeap)>::type::element_type;
      RInterface<BaseNodeType_t> upcastInterface(*upcastNodeOnHeap, *fLoopManager, fCustomColumns, fDataSource);

      auto jittedActionOnHeap =
         RDFInternal::MakeSharedOnHeap(std::make_shared<RDFInternal::RJittedAction>(*fLoopManager));

      auto toJit = RDFInternal::JitBuildAction(
         validColumnNames, upcastNodeOnHeap, typeid(std::shared_ptr<ActionResultType>), typeid(ActionTag), rOnHeap,
         tree, nSlots, fCustomColumns, fDataSource, jittedActionOnHeap, fLoopManager->GetID());
      fLoopManager->Book(jittedActionOnHeap->get());
      fLoopManager->ToJitExec(toJit);
      return MakeResultPtr(r, *fLoopManager, *jittedActionOnHeap);
   }

   template <typename F, typename CustomColumnType, typename RetType = typename TTraits::CallableTraits<F>::ret_type>
   typename std::enable_if<std::is_default_constructible<RetType>::value, RInterface<Proxied, DS_t>>::type
   DefineImpl(std::string_view name, F &&expression, const ColumnNames_t &columns)
   {
      RDFInternal::CheckCustomColumn(name, fLoopManager->GetTree(), fCustomColumns.GetNames(),
                                     fLoopManager->GetAliasMap(),
                                     fDataSource ? fDataSource->GetColumnNames() : ColumnNames_t{});

      using ArgTypes_t = typename TTraits::CallableTraits<F>::arg_types;
      using ColTypesTmp_t = typename RDFInternal::RemoveFirstParameterIf<
         std::is_same<CustomColumnType, RDFDetail::CustomColExtraArgs::Slot>::value, ArgTypes_t>::type;
      using ColTypes_t = typename RDFInternal::RemoveFirstTwoParametersIf<
         std::is_same<CustomColumnType, RDFDetail::CustomColExtraArgs::SlotAndEntry>::value, ColTypesTmp_t>::type;

      constexpr auto nColumns = ColTypes_t::list_size;

      const auto validColumnNames = GetValidatedColumnNames(nColumns, columns);

      auto newColumns = CheckAndFillDSColumns(validColumnNames, std::make_index_sequence<nColumns>(), ColTypes_t());

      using NewCol_t = RDFDetail::RCustomColumn<F, CustomColumnType>;
      RDFInternal::RBookedCustomColumns newCols(newColumns);
      auto newColumn = std::make_shared<NewCol_t>(fLoopManager, name, std::forward<F>(expression), validColumnNames,
                                                  fLoopManager->GetNSlots(), newCols);

      // Declare return type to the interpreter, for future use by jitted actions
      auto retTypeName = RDFInternal::TypeID2TypeName(typeid(RetType));
      if (retTypeName.empty()) {
         // The type is not known to the interpreter.
         // Forward-declare it as void + helpful comment, so that if this Define'd quantity is
         // ever used by jitted code users will have some way to know what went wrong
         const auto demangledType = RDFInternal::DemangleTypeIdName(typeid(RetType));
         retTypeName = "void /* The type of column \"" + std::string(name) + "\" (" + demangledType +
                       ") is not known to the interpreter. */";
      }
      const auto retTypeDeclaration = "namespace __rdf" + std::to_string(fLoopManager->GetID()) +
                                      " { " + +" using " + std::string(name) + std::to_string(newColumn->GetID()) +
                                      "_type = " + retTypeName + "; }";
      fLoopManager->ToJitDeclare(retTypeDeclaration);

      fLoopManager->RegisterCustomColumn(newColumn.get());
      newCols.AddName(name);
      newCols.AddColumn(newColumn, name);

      RInterface<Proxied> newInterface(fProxiedPtr, *fLoopManager, std::move(newCols), fDataSource);

      return newInterface;
   }

   // This overload is chosen when the callable passed to Define or DefineSlot returns void.
   // It simply fires a compile-time error. This is preferable to a static_assert in the main `Define` overload because
   // this way compilation of `Define` has no way to continue after throwing the error.
   template <typename F, typename CustomColumnType, typename RetType = typename TTraits::CallableTraits<F>::ret_type,
             bool IsFStringConv = std::is_convertible<F, std::string>::value,
             bool IsRetTypeDefConstr = std::is_default_constructible<RetType>::value>
   typename std::enable_if<!IsFStringConv && !IsRetTypeDefConstr, RInterface<Proxied, DS_t>>::type
   DefineImpl(std::string_view, F, const ColumnNames_t &)
   {
      static_assert(std::is_default_constructible<typename TTraits::CallableTraits<F>::ret_type>::value,
                    "Error in `Define`: type returned by expression is not default-constructible");
      return *this; // never reached
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Implementation of snapshot
   /// \param[in] treename The name of the TTree
   /// \param[in] filename The name of the TFile
   /// \param[in] columnList The list of names of the branches to be written
   /// The implementation exploits Foreach. The association of the addresses to
   /// the branches takes place at the first event. This is possible because
   /// since there are no copies, the address of the value passed by reference
   /// is the address pointing to the storage of the read/created object in/by
   /// the TTreeReaderValue/TemporaryBranch
   template <typename... ColumnTypes>
   RResultPtr<RInterface<RLoopManager>> SnapshotImpl(std::string_view treename, std::string_view filename,
                                                     const ColumnNames_t &columnList, const RSnapshotOptions &options)
   {
      RDFInternal::CheckTypesAndPars(sizeof...(ColumnTypes), columnList.size());

      const auto validCols = GetValidatedColumnNames(columnList.size(), columnList);

      auto newColumns = CheckAndFillDSColumns(validCols, std::index_sequence_for<ColumnTypes...>(),
                                              TTraits::TypeList<ColumnTypes...>());

      const std::string fullTreename(treename);
      // split name into directory and treename if needed
      const auto lastSlash = treename.rfind('/');
      std::string_view dirname = "";
      if (std::string_view::npos != lastSlash) {
         dirname = treename.substr(0, lastSlash);
         treename = treename.substr(lastSlash + 1, treename.size());
      }

      // add action node to functional graph and run event loop
      std::unique_ptr<RDFInternal::RActionBase> actionPtr;
      if (!ROOT::IsImplicitMTEnabled()) {
         // single-thread snapshot
         using Helper_t = RDFInternal::SnapshotHelper<ColumnTypes...>;
         using Action_t = RDFInternal::RAction<Helper_t, Proxied>;
         actionPtr.reset(new Action_t(Helper_t(filename, dirname, treename, validCols, columnList, options), validCols,
                                      fProxiedPtr, std::move(newColumns)));
      } else {
         // multi-thread snapshot
         using Helper_t = RDFInternal::SnapshotHelperMT<ColumnTypes...>;
         using Action_t = RDFInternal::RAction<Helper_t, Proxied>;
         actionPtr.reset(new Action_t(
            Helper_t(fLoopManager->GetNSlots(), filename, dirname, treename, validCols, columnList, options), validCols,
            fProxiedPtr, std::move(newColumns)));
      }

      fLoopManager->Book(actionPtr.get());

      return RDFInternal::CreateSnapshotRDF(validCols, fullTreename, filename, options.fLazy, *fLoopManager,
                                           std::move(actionPtr));
   }

   ////////////////////////////////////////////////////////////////////////////
   /// \brief Implementation of cache
   template <typename... BranchTypes, std::size_t... S>
   RInterface<RLoopManager> CacheImpl(const ColumnNames_t &columnList, std::index_sequence<S...> s)
   {
      // Check at compile time that the columns types are copy constructible
      constexpr bool areCopyConstructible =
         RDFInternal::TEvalAnd<std::is_copy_constructible<BranchTypes>::value...>::value;
      static_assert(areCopyConstructible, "Columns of a type which is not copy constructible cannot be cached yet.");

      // We share bits and pieces with snapshot. De facto this is a snapshot
      // in memory!
      RDFInternal::CheckTypesAndPars(sizeof...(BranchTypes), columnList.size());

      auto colHolders = std::make_tuple(Take<BranchTypes>(columnList[S])...);
      auto ds = std::make_unique<RLazyDS<BranchTypes...>>(std::make_pair(columnList[S], std::get<S>(colHolders))...);

      RInterface<RLoopManager> cachedRDF(std::make_shared<RLoopManager>(std::move(ds), columnList));

      (void)s; // Prevents unused warning

      return cachedRDF;
   }

protected:
   RInterface(const std::shared_ptr<Proxied> &proxied, RLoopManager &lm,
              const RDFInternal::RBookedCustomColumns &columns, RDataSource *ds)
      : fProxiedPtr(proxied), fLoopManager(&lm), fDataSource(ds), fCustomColumns(columns)
   {
   }

   RLoopManager *GetLoopManager() const { return fLoopManager; }

   const std::shared_ptr<Proxied> &GetProxiedPtr() const { return fProxiedPtr; }

   /// Prepare the call to the GetValidatedColumnNames routine, making sure that GetBranchNames,
   /// which is expensive in terms of runtime, is called at most once.
   ColumnNames_t GetValidatedColumnNames(const unsigned int nColumns, const ColumnNames_t &columns)
   {
      return RDFInternal::GetValidatedColumnNames(*fLoopManager, nColumns, columns, fCustomColumns.GetNames(),
                                                  fDataSource);
   }

   template <typename... ColumnTypes, std::size_t... S>
   RDFInternal::RBookedCustomColumns
   CheckAndFillDSColumns(ColumnNames_t validCols, std::index_sequence<S...>, TTraits::TypeList<ColumnTypes...>)
   {
      return fDataSource
                ? RDFInternal::AddDSColumns(*fLoopManager, validCols, fCustomColumns, *fDataSource,
                                            fLoopManager->GetNSlots(), std::index_sequence_for<ColumnTypes...>(),
                                            TTraits::TypeList<ColumnTypes...>())
                : fCustomColumns;
   }
};

} // end NS RDF

} // namespace ROOT

#endif // ROOT_RDF_INTERFACE