Converts a TTree into an RNTuple.

Example usage (see the ntpl008_import.C tutorial for a full example):

#include <ROOT/RNTupleImporter.hxx>
using ROOT::Experimental::RNTupleImporter;
 
auto importer = RNTupleImporter::Create("data.root", "TreeName", "output.root");
// As required: importer->SetNTupleName(), importer->SetWriteOptions(), ...
importer->Import();

The output file is created if it does not exist, otherwise the ntuple is added to the existing file. Note that input file and output file can be identical if the ntuple is stored under a different name than the tree (use SetNTupleName()).

By default, the RNTuple is compressed with zstd, independent of the input compression. The compression settings (and other output parameters) can be changed by SetWriteOptions(). For example, to compress the imported RNTuple using lz4 (with compression level 4) instead:

auto writeOptions = importer->GetWriteOptions();
writeOptions.SetCompression(404);
importer->SetWriteOptions(writeOptions);

Most RNTuple fields have a type identical to the corresponding TTree input branch. Exceptions are

C string branches are translated to std::string fields
C style arrays are translated to std::array<...> fields
Leaf lists are translated to untyped records
Leaf count arrays are translated to anonymous collections with generic names (_collection0, _collection1, etc.). In order to keep field names and branch names aligned, RNTuple projects the members of these collections and its collection counter to the input branch names. For instance, the following input leafs:
Int_t njets

float jet_pt[njets]

float jet_eta[njets]

int

will be converted to the following RNTuple schema:
_collection0 (untyped collection)

|- float jet_pt

|- float jet_eta

std::size_t (RNTupleCardinality) njets (projected from _collection0 without subfields)

ROOT::RVec<float> jet_pt (projected from _collection0.jet_pt)

ROOT::RVec<float> jet_eta (projected from _collection0.jet_eta)

ROOT::VecOps::RVec
A "std::vector"-like collection of values implementing handy operation to analyse them.
Definition RVec.hxx:1529

ROOT::Experimental::RNTupleCardinality
Helper types to present an offset column as array of collection sizes.
Definition RNTupleUtil.hxx:71

These projections are meta-data only operations and don't involve duplicating the data.

Current limitations of the importer:

No support for trees containing TClonesArray collections
Due to RNTuple currently storing data fully split, "don't split" markers are ignored
Some types are not available in RNTuple. Please refer to the RNTuple specification for an overview of all types currently supported.

Definition at line 103 of file RNTupleImporter.hxx.

Classes
struct	RCStringTransformation
	Transform a NULL terminated C string branch into an `std::string` field. More...

struct	RImportBranch

struct	RImportField

struct	RImportGuard
	When the schema is set up and the import started, it needs to be reset before the next Import() call can start. More...

struct	RImportLeafCountCollection
	Leaf count arrays require special treatment. More...

struct	RImportTransformation
	Base class to perform data transformations from TTree branches to RNTuple fields if necessary. More...

struct	RLeafArrayTransformation
	When writing the elements of a leaf count array, moves the data from the input array one-by-one to the memory locations of the fields of the corresponding untyped collection. More...

class	RProgressCallback
	Used to report every ~50MB (compressed), and at the end about the status of the import. More...

Public Member Functions
	RNTupleImporter (const RNTupleImporter &other)=delete

	RNTupleImporter (RNTupleImporter &&other)=delete

	~RNTupleImporter ()=default

RNTupleWriteOptions	GetWriteOptions () const

void	Import ()
	Import works in two steps:

RNTupleImporter &	operator= (const RNTupleImporter &other)=delete

RNTupleImporter &	operator= (RNTupleImporter &&other)=delete

void	SetConvertDotsInBranchNames (bool value)
	Whereas branch names may contain dots, RNTuple field names may not.

void	SetIsQuiet (bool value)
	Whether or not information and progress is printed to stdout.

void	SetMaxEntries (std::uint64_t maxEntries)

void	SetNTupleName (const std::string &name)

void	SetWriteOptions (RNTupleWriteOptions options)

Static Public Member Functions
static std::unique_ptr< RNTupleImporter >	Create (std::string_view sourceFileName, std::string_view treeName, std::string_view destFileName)
	Opens the input file for reading and the output file for writing (update).

static std::unique_ptr< RNTupleImporter >	Create (TTree *sourceTree, std::string_view destFileName)
	Directly uses the provided tree and opens the output file for writing (update).

Private Member Functions
	RNTupleImporter ()=default

ROOT::Experimental::RResult< void >	InitDestination (std::string_view destFileName)

RResult< void >	PrepareSchema ()
	Sets up the connection from TTree branches to RNTuple fields, including initialization of the memory buffers used for reading and writing.

void	ReportSchema ()

void	ResetSchema ()

Private Attributes
bool	fConvertDotsInBranchNames = false
	Whether or not dot characters in branch names should be converted to underscores.

std::unique_ptr< TFile >	fDestFile

std::string	fDestFileName

std::unique_ptr< REntry >	fEntry

std::vector< RImportBranch >	fImportBranches

std::vector< RImportField >	fImportFields

std::vector< std::unique_ptr< RImportTransformation > >	fImportTransformations
	The list of transformations to be performed for every entry.

bool	fIsQuiet = false
	No standard output, conversely if set to false, schema information and progress is printed.

std::map< std::string, RImportLeafCountCollection >	fLeafCountCollections
	Maps the count leaf to the information about the corresponding untyped collection.

std::int64_t	fMaxEntries = -1
	The maximum number of entries to import. When this value is -1 (default), import all entries.

std::unique_ptr< RNTupleModel >	fModel

std::string	fNTupleName

std::unique_ptr< RProgressCallback >	fProgressCallback

std::unique_ptr< TFile >	fSourceFile

TTree *	fSourceTree

RNTupleWriteOptions	fWriteOptions

#include <ROOT/RNTupleImporter.hxx>

Constructor & Destructor Documentation

◆ RNTupleImporter() [1/3]

ROOT::Experimental::RNTupleImporter::RNTupleImporter ( )

privatedefault

◆ RNTupleImporter() [2/3]

ROOT::Experimental::RNTupleImporter::RNTupleImporter ( const RNTupleImporter & other )

delete

◆ RNTupleImporter() [3/3]

ROOT::Experimental::RNTupleImporter::RNTupleImporter ( RNTupleImporter && other )

delete

◆ ~RNTupleImporter()

ROOT::Experimental::RNTupleImporter::~RNTupleImporter ( )

default

Member Function Documentation

◆ Create() [1/2]

std::unique_ptr< ROOT::Experimental::RNTupleImporter > ROOT::Experimental::RNTupleImporter::Create	(	std::string_view	sourceFileName,
		std::string_view	treeName,
		std::string_view	destFileName
	)

static

Opens the input file for reading and the output file for writing (update).

Definition at line 90 of file RNTupleImporter.cxx.

◆ Create() [2/2]

std::unique_ptr< ROOT::Experimental::RNTupleImporter > ROOT::Experimental::RNTupleImporter::Create	(	TTree *	sourceTree,
		std::string_view	destFileName
	)

static

Directly uses the provided tree and opens the output file for writing (update).

Definition at line 116 of file RNTupleImporter.cxx.

◆ GetWriteOptions()

RNTupleWriteOptions ROOT::Experimental::RNTupleImporter::GetWriteOptions ( ) const

inline

Definition at line 263 of file RNTupleImporter.hxx.

◆ Import()

void ROOT::Experimental::RNTupleImporter::Import ( )

Import works in two steps:

PrepareSchema() calls SetBranchAddress() on all the TTree branches and creates the corresponding RNTuple fields and the model
An event loop reads every entry from the TTree, applies transformations where necessary, and writes the output entry to the RNTuple.

Definition at line 374 of file RNTupleImporter.cxx.

◆ InitDestination()

ROOT::Experimental::RResult< void > ROOT::Experimental::RNTupleImporter::InitDestination ( std::string_view destFileName )

private

Definition at line 140 of file RNTupleImporter.cxx.

◆ operator=() [1/2]

RNTupleImporter & ROOT::Experimental::RNTupleImporter::operator= ( const RNTupleImporter & other )

delete

◆ operator=() [2/2]

RNTupleImporter & ROOT::Experimental::RNTupleImporter::operator= ( RNTupleImporter && other )

delete

◆ PrepareSchema()

ROOT::Experimental::RResult< void > ROOT::Experimental::RNTupleImporter::PrepareSchema ( )

private

Sets up the connection from TTree branches to RNTuple fields, including initialization of the memory buffers used for reading and writing.

Definition at line 168 of file RNTupleImporter.cxx.

◆ ReportSchema()

void ROOT::Experimental::RNTupleImporter::ReportSchema ( )

private

Definition at line 151 of file RNTupleImporter.cxx.

◆ ResetSchema()

void ROOT::Experimental::RNTupleImporter::ResetSchema ( )

private

Definition at line 158 of file RNTupleImporter.cxx.

◆ SetConvertDotsInBranchNames()

void ROOT::Experimental::RNTupleImporter::SetConvertDotsInBranchNames ( bool value )

inline

Whereas branch names may contain dots, RNTuple field names may not.

By setting this option, dot characters are automatically converted into underscores to prevent the importer from throwing an exception.

Definition at line 270 of file RNTupleImporter.hxx.

◆ SetIsQuiet()

void ROOT::Experimental::RNTupleImporter::SetIsQuiet ( bool value )

inline

Whether or not information and progress is printed to stdout.

Definition at line 273 of file RNTupleImporter.hxx.

◆ SetMaxEntries()

void ROOT::Experimental::RNTupleImporter::SetMaxEntries ( std::uint64_t maxEntries )

inline

Definition at line 266 of file RNTupleImporter.hxx.

◆ SetNTupleName()

void ROOT::Experimental::RNTupleImporter::SetNTupleName ( const std::string & name )

inline

Definition at line 265 of file RNTupleImporter.hxx.

◆ SetWriteOptions()

void ROOT::Experimental::RNTupleImporter::SetWriteOptions ( RNTupleWriteOptions options )

inline

Definition at line 264 of file RNTupleImporter.hxx.

Member Data Documentation

◆ fConvertDotsInBranchNames

bool ROOT::Experimental::RNTupleImporter::fConvertDotsInBranchNames = false

private

Whether or not dot characters in branch names should be converted to underscores.

If this option is not set and a branch with a '.' is encountered, the importer will throw an exception.

Definition at line 223 of file RNTupleImporter.hxx.

◆ fDestFile

std::unique_ptr<TFile> ROOT::Experimental::RNTupleImporter::fDestFile

private

Definition at line 218 of file RNTupleImporter.hxx.

◆ fDestFileName

std::string ROOT::Experimental::RNTupleImporter::fDestFileName

private

Definition at line 216 of file RNTupleImporter.hxx.

◆ fEntry

std::unique_ptr<REntry> ROOT::Experimental::RNTupleImporter::fEntry

private

Definition at line 233 of file RNTupleImporter.hxx.

◆ fImportBranches

std::vector<RImportBranch> ROOT::Experimental::RNTupleImporter::fImportBranches

private

Definition at line 234 of file RNTupleImporter.hxx.

◆ fImportFields

std::vector<RImportField> ROOT::Experimental::RNTupleImporter::fImportFields

private

Definition at line 235 of file RNTupleImporter.hxx.

◆ fImportTransformations

std::vector<std::unique_ptr<RImportTransformation> > ROOT::Experimental::RNTupleImporter::fImportTransformations

private

The list of transformations to be performed for every entry.

Definition at line 239 of file RNTupleImporter.hxx.

◆ fIsQuiet

bool ROOT::Experimental::RNTupleImporter::fIsQuiet = false

private

No standard output, conversely if set to false, schema information and progress is printed.

Definition at line 229 of file RNTupleImporter.hxx.

◆ fLeafCountCollections

std::map<std::string, RImportLeafCountCollection> ROOT::Experimental::RNTupleImporter::fLeafCountCollections

private

Maps the count leaf to the information about the corresponding untyped collection.

Definition at line 237 of file RNTupleImporter.hxx.

◆ fMaxEntries

std::int64_t ROOT::Experimental::RNTupleImporter::fMaxEntries = -1

private

The maximum number of entries to import. When this value is -1 (default), import all entries.

Definition at line 226 of file RNTupleImporter.hxx.

◆ fModel

std::unique_ptr<RNTupleModel> ROOT::Experimental::RNTupleImporter::fModel

private

Definition at line 232 of file RNTupleImporter.hxx.

◆ fNTupleName

std::string ROOT::Experimental::RNTupleImporter::fNTupleName

private

Definition at line 217 of file RNTupleImporter.hxx.

◆ fProgressCallback

std::unique_ptr<RProgressCallback> ROOT::Experimental::RNTupleImporter::fProgressCallback

private

Definition at line 230 of file RNTupleImporter.hxx.

◆ fSourceFile

std::unique_ptr<TFile> ROOT::Experimental::RNTupleImporter::fSourceFile

private

Definition at line 213 of file RNTupleImporter.hxx.

◆ fSourceTree

TTree* ROOT::Experimental::RNTupleImporter::fSourceTree

private

Definition at line 214 of file RNTupleImporter.hxx.

◆ fWriteOptions

RNTupleWriteOptions ROOT::Experimental::RNTupleImporter::fWriteOptions

private

Definition at line 219 of file RNTupleImporter.hxx.

Libraries for ROOT::Experimental::RNTupleImporter:

[legend]

The documentation for this class was generated from the following files:

tree/ntupleutil/v7/inc/ROOT/RNTupleImporter.hxx
tree/ntupleutil/v7/src/RNTupleImporter.cxx

Classes

Public Member Functions

Static Public Member Functions

Private Member Functions

Private Attributes

Constructor & Destructor Documentation

◆ RNTupleImporter() [1/3]

◆ RNTupleImporter() [2/3]

◆ RNTupleImporter() [3/3]

◆ ~RNTupleImporter()

Member Function Documentation

◆ Create() [1/2]

◆ Create() [2/2]

◆ GetWriteOptions()

◆ Import()

◆ InitDestination()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ PrepareSchema()

◆ ReportSchema()

◆ ResetSchema()

◆ SetConvertDotsInBranchNames()

◆ SetIsQuiet()

◆ SetMaxEntries()

◆ SetNTupleName()

◆ SetWriteOptions()

Member Data Documentation

◆ fConvertDotsInBranchNames

◆ fDestFile

◆ fDestFileName

◆ fEntry

◆ fImportBranches

◆ fImportFields

◆ fImportTransformations

◆ fIsQuiet

◆ fLeafCountCollections

◆ fMaxEntries

◆ fModel

◆ fNTupleName

◆ fProgressCallback

◆ fSourceFile

◆ fSourceTree

◆ fWriteOptions