The RNTupleModel encapulates the schema of an ntuple.

The ntuple model comprises a collection of hierarchically organized fields. From a model, "entries" can be extracted. For convenience, the model provides a default entry unless it is created as a "bare model". Models have a unique model identifier that faciliates checking whether entries are compatible with it (i.e.: have been extracted from that model).

A model is subject to a state transition during its lifetime: it starts in a building state, in which fields can be added and modified. Once the schema is finalized, the model gets frozen. Only frozen models can create entries.

Definition at line 136 of file RNTupleModel.hxx.

Classes
struct	NameWithDescription_t
	A wrapper over a field name and an optional description; used in `AddField()` and `RUpdater::AddField()` More...

class	RUpdater
	A model is usually immutable after passing it to an `RNTupleWriter`. More...

Public Types
using	FieldMappingFunc_t = std::function< std::string(const std::string &)>
	User provided function that describes the mapping of existing source fields to projected fields in terms of fully qualified field names.

Public Member Functions
	RNTupleModel (const RNTupleModel &)=delete

	~RNTupleModel ()=default

void	AddField (std::unique_ptr< RFieldBase > field)
	Adds a field whose type is not known at compile time.

RResult< void >	AddProjectedField (std::unique_ptr< RFieldBase > field, FieldMappingFunc_t mapping)
	Adds a top-level field based on existing fields.

std::unique_ptr< RNTupleModel >	Clone () const

std::unique_ptr< REntry >	CreateBareEntry () const
	In a bare entry, all values point to nullptr.

RFieldBase::RBulk	CreateBulk (std::string_view fieldName) const
	Calls the given field's CreateBulk() method. Throws an exception if no field with the given name exists.

std::unique_ptr< REntry >	CreateEntry () const

std::size_t	EstimateWriteMemoryUsage (const RNTupleWriteOptions &options=RNTupleWriteOptions()) const
	Estimate the memory usage for this model during writing.

void	Freeze ()

const RFieldBase &	GetConstField (std::string_view fieldName) const

const RFieldZero &	GetConstFieldZero () const

REntry &	GetDefaultEntry ()

const REntry &	GetDefaultEntry () const

const std::string &	GetDescription () const

std::uint64_t	GetModelId () const

RFieldBase &	GetMutableField (std::string_view fieldName)

RFieldZero &	GetMutableFieldZero ()
	Mutable access to the root field is used to make adjustments to the fields.

const std::unordered_set< std::string > &	GetRegisteredSubfields () const
	Get the (qualified) names of subfields that have been registered to be included in entries from this model.

std::uint64_t	GetSchemaId () const

REntry::RFieldToken	GetToken (std::string_view fieldName) const
	Creates a token to be used in REntry methods to address a field present in the entry.

bool	IsBare () const

bool	IsFrozen () const

template<typename T , typename... ArgsT>
std::shared_ptr< T >	MakeField (const NameWithDescription_t &fieldNameDesc, ArgsT &&...args)
	Creates a new field given a `name` or `{name, description}` pair and a corresponding value that is managed by a shared pointer.

RNTupleModel &	operator= (const RNTupleModel &)=delete

void	RegisterSubfield (std::string_view qualifiedFieldName)
	Register a subfield so it can be accessed directly from entries belonging to the model.

void	SetDescription (std::string_view description)

void	Unfreeze ()

Static Public Member Functions
static std::unique_ptr< RNTupleModel >	Create ()

static std::unique_ptr< RNTupleModel >	Create (std::unique_ptr< RFieldZero > fieldZero)

static std::unique_ptr< RNTupleModel >	CreateBare ()
	A bare model has no default entry.

static std::unique_ptr< RNTupleModel >	CreateBare (std::unique_ptr< RFieldZero > fieldZero)

Private Member Functions
	RNTupleModel (std::unique_ptr< RFieldZero > fieldZero)

void	AddSubfield (std::string_view fieldName, REntry &entry, bool initializeValue=true) const
	Add a subfield to the provided entry.

void	EnsureNotBare () const
	Throws an RException if fDefaultEntry is nullptr.

void	EnsureNotFrozen () const
	Throws an RException if fFrozen is true.

void	EnsureValidFieldName (std::string_view fieldName)
	Checks that user-provided field names are valid in the context of this RNTuple model.

RFieldBase *	FindField (std::string_view fieldName) const
	The field name can be a top-level field or a nested field. Returns nullptr if the field is not in the model.

Private Attributes
std::unique_ptr< REntry >	fDefaultEntry
	Contains field values corresponding to the created top-level fields, as well as registered subfields.

std::string	fDescription
	Free text set by the user.

std::unordered_set< std::string >	fFieldNames
	Keeps track of which field names are taken, including projected field names.

std::unique_ptr< RFieldZero >	fFieldZero
	Hierarchy of fields consisting of simple types and collections (sub trees)

bool	fIsFrozen = false
	Changed by Freeze() / Unfreeze() and by the RUpdater.

std::uint64_t	fModelId = 0
	Every model has a unique ID to distinguish it from other models.

std::unique_ptr< Internal::RProjectedFields >	fProjectedFields
	The set of projected top-level fields.

std::unordered_set< std::string >	fRegisteredSubfields
	Keeps track of which subfields have been registered to be included in entries belonging to this model.

std::uint64_t	fSchemaId = 0
	Models have a separate schema ID to remember that the clone of a frozen model still has the same schema.

Friends
RFieldZero &	Internal::GetFieldZeroOfModel (RNTupleModel &)

Internal::RProjectedFields &	Internal::GetProjectedFieldsOfModel (RNTupleModel &)

#include <ROOT/RNTupleModel.hxx>

Member Typedef Documentation

◆ FieldMappingFunc_t

using ROOT::Experimental::RNTupleModel::FieldMappingFunc_t = std::function<std::string(const std::string &)>

User provided function that describes the mapping of existing source fields to projected fields in terms of fully qualified field names.

The mapping function is called with the qualified field names of the provided field and the subfields. It should return the qualified field names used as a mapping source.

Definition at line 144 of file RNTupleModel.hxx.

Constructor & Destructor Documentation

◆ RNTupleModel() [1/2]

ROOT::Experimental::RNTupleModel::RNTupleModel ( std::unique_ptr< RFieldZero > fieldZero )

private

Definition at line 235 of file RNTupleModel.cxx.

◆ RNTupleModel() [2/2]

ROOT::Experimental::RNTupleModel::RNTupleModel ( const RNTupleModel & )

delete

◆ ~RNTupleModel()

ROOT::Experimental::RNTupleModel::~RNTupleModel ( )

default

Member Function Documentation

◆ AddField()

void ROOT::Experimental::RNTupleModel::AddField ( std::unique_ptr< RFieldBase > field )

Adds a field whose type is not known at compile time.

Thus there is no shared pointer returned.

Throws an exception if the field is null.

Definition at line 315 of file RNTupleModel.cxx.

◆ AddProjectedField()

ROOT::Experimental::RResult< void > ROOT::Experimental::RNTupleModel::AddProjectedField	(	std::unique_ptr< RFieldBase >	field,
		FieldMappingFunc_t	mapping
	)

Adds a top-level field based on existing fields.

The mapping function takes one argument, which is a string containing the name of the projected field. The return value of the mapping function should be the name of the (existing) field onto which the projection is made. Example

auto model = RNTupleModel::Create();
model->MakeField<float>("met");
auto metProjection = RFieldBase::Create("missingE", "float").Unwrap();
model->AddProjectedField(std::move(metProjection), [](const std::string &) { return "met"; });

Adding projections for collection fields is also possible, as long as they follow the same schema structure. For example, a projection of a collection of structs onto a collection of scalars is possible, but a projection of a collection of a collection of scalars onto a collection of scalars is not.

In the case of projections for nested fields, the mapping function must provide a mapping for every nesting level. Example

struct P { int x, y; };
 
auto model = RNTupleModel::Create();
model->MakeField<std::vector<P>>("points");
auto pxProjection = RFieldBase::Create("pxs", "std::vector<int>").Unwrap();
model->AddProjectedField(std::move(pxProjection), [](const std::string &fieldName) {
  if (fieldName == "pxs")
    return "points";
  else
    return "points._0.x";
});

Creating projections for fields containing std::variant or fixed-size arrays is unsupported.

Definition at line 374 of file RNTupleModel.cxx.

◆ AddSubfield()

void ROOT::Experimental::RNTupleModel::AddSubfield	(	std::string_view	fieldName,
		REntry &	entry,
		bool	initializeValue = `true`
	)		const

private

Add a subfield to the provided entry.

If initializeValue is false, a nullptr will be bound to the entry value (used in bare models).

Definition at line 328 of file RNTupleModel.cxx.

◆ Clone()

std::unique_ptr< ROOT::Experimental::RNTupleModel > ROOT::Experimental::RNTupleModel::Clone ( ) const

Definition at line 265 of file RNTupleModel.cxx.

◆ Create() [1/2]

std::unique_ptr< ROOT::Experimental::RNTupleModel > ROOT::Experimental::RNTupleModel::Create ( )

static

Definition at line 252 of file RNTupleModel.cxx.

◆ Create() [2/2]

std::unique_ptr< ROOT::Experimental::RNTupleModel > ROOT::Experimental::RNTupleModel::Create ( std::unique_ptr< RFieldZero > fieldZero )

static

Definition at line 258 of file RNTupleModel.cxx.

◆ CreateBare() [1/2]

std::unique_ptr< ROOT::Experimental::RNTupleModel > ROOT::Experimental::RNTupleModel::CreateBare ( )

static

A bare model has no default entry.

Definition at line 239 of file RNTupleModel.cxx.

◆ CreateBare() [2/2]

std::unique_ptr< ROOT::Experimental::RNTupleModel > ROOT::Experimental::RNTupleModel::CreateBare ( std::unique_ptr< RFieldZero > fieldZero )

static

Definition at line 245 of file RNTupleModel.cxx.

◆ CreateBareEntry()

std::unique_ptr< ROOT::Experimental::REntry > ROOT::Experimental::RNTupleModel::CreateBareEntry ( ) const

In a bare entry, all values point to nullptr.

The resulting entry shall use BindValue() in order set memory addresses to be serialized / deserialized

Definition at line 458 of file RNTupleModel.cxx.

◆ CreateBulk()

ROOT::Experimental::RFieldBase::RBulk ROOT::Experimental::RNTupleModel::CreateBulk ( std::string_view fieldName ) const

Calls the given field's CreateBulk() method. Throws an exception if no field with the given name exists.

Definition at line 485 of file RNTupleModel.cxx.

◆ CreateEntry()

std::unique_ptr< ROOT::Experimental::REntry > ROOT::Experimental::RNTupleModel::CreateEntry ( ) const

Definition at line 443 of file RNTupleModel.cxx.

◆ EnsureNotBare()

void ROOT::Experimental::RNTupleModel::EnsureNotBare ( ) const

private

Throws an RException if fDefaultEntry is nullptr.

Definition at line 229 of file RNTupleModel.cxx.

◆ EnsureNotFrozen()

void ROOT::Experimental::RNTupleModel::EnsureNotFrozen ( ) const

private

Throws an RException if fFrozen is true.

Definition at line 223 of file RNTupleModel.cxx.

◆ EnsureValidFieldName()

void ROOT::Experimental::RNTupleModel::EnsureValidFieldName ( std::string_view fieldName )

private

Checks that user-provided field names are valid in the context of this RNTuple model.

Throws an RException for invalid names, empty names (which is reserved for the zero field) and duplicate field names.

Definition at line 209 of file RNTupleModel.cxx.

◆ EstimateWriteMemoryUsage()

std::size_t ROOT::Experimental::RNTupleModel::EstimateWriteMemoryUsage ( const RNTupleWriteOptions & options = RNTupleWriteOptions() ) const

Estimate the memory usage for this model during writing.

This will return an estimate in bytes for the internal page and compression buffers. The value should be understood per sequential RNTupleWriter or per RNTupleFillContext created for a RNTupleParallelWriter constructed with this model.

Definition at line 521 of file RNTupleModel.cxx.

◆ FindField()

ROOT::Experimental::RFieldBase * ROOT::Experimental::RNTupleModel::FindField ( std::string_view fieldName ) const

private

The field name can be a top-level field or a nested field. Returns nullptr if the field is not in the model.

Definition at line 294 of file RNTupleModel.cxx.

◆ Freeze()

void ROOT::Experimental::RNTupleModel::Freeze ( )

Definition at line 510 of file RNTupleModel.cxx.

◆ GetConstField()

const ROOT::Experimental::RFieldBase & ROOT::Experimental::RNTupleModel::GetConstField ( std::string_view fieldName ) const

Definition at line 420 of file RNTupleModel.cxx.

◆ GetConstFieldZero()

const RFieldZero & ROOT::Experimental::RNTupleModel::GetConstFieldZero ( ) const

inline

Definition at line 383 of file RNTupleModel.hxx.

◆ GetDefaultEntry() [1/2]

ROOT::Experimental::REntry & ROOT::Experimental::RNTupleModel::GetDefaultEntry ( )

Definition at line 429 of file RNTupleModel.cxx.

◆ GetDefaultEntry() [2/2]

const ROOT::Experimental::REntry & ROOT::Experimental::RNTupleModel::GetDefaultEntry ( ) const

Definition at line 435 of file RNTupleModel.cxx.

◆ GetDescription()

const std::string & ROOT::Experimental::RNTupleModel::GetDescription ( ) const

inline

Definition at line 387 of file RNTupleModel.hxx.

◆ GetModelId()

std::uint64_t ROOT::Experimental::RNTupleModel::GetModelId ( ) const

inline

Definition at line 366 of file RNTupleModel.hxx.

◆ GetMutableField()

ROOT::Experimental::RFieldBase & ROOT::Experimental::RNTupleModel::GetMutableField ( std::string_view fieldName )

Definition at line 409 of file RNTupleModel.cxx.

◆ GetMutableFieldZero()

ROOT::Experimental::RFieldZero & ROOT::Experimental::RNTupleModel::GetMutableFieldZero ( )

Mutable access to the root field is used to make adjustments to the fields.

Definition at line 402 of file RNTupleModel.cxx.

◆ GetRegisteredSubfields()

const std::unordered_set< std::string > & ROOT::Experimental::RNTupleModel::GetRegisteredSubfields ( ) const

inline

Get the (qualified) names of subfields that have been registered to be included in entries from this model.

Definition at line 391 of file RNTupleModel.hxx.

◆ GetSchemaId()

std::uint64_t ROOT::Experimental::RNTupleModel::GetSchemaId ( ) const

inline

Definition at line 367 of file RNTupleModel.hxx.

◆ GetToken()

ROOT::Experimental::REntry::RFieldToken ROOT::Experimental::RNTupleModel::GetToken ( std::string_view fieldName ) const

Creates a token to be used in REntry methods to address a field present in the entry.

Definition at line 473 of file RNTupleModel.cxx.

◆ IsBare()

bool ROOT::Experimental::RNTupleModel::IsBare ( ) const

inline

Definition at line 365 of file RNTupleModel.hxx.

◆ IsFrozen()

bool ROOT::Experimental::RNTupleModel::IsFrozen ( ) const

inline

Definition at line 364 of file RNTupleModel.hxx.

◆ MakeField()

template<typename T , typename... ArgsT>

std::shared_ptr< T > ROOT::Experimental::RNTupleModel::MakeField	(	const NameWithDescription_t &	fieldNameDesc,
		ArgsT &&...	args
	)

inline

Creates a new field given a name or {name, description} pair and a corresponding value that is managed by a shared pointer.

Example: create some fields and fill an RNTuple

#include <ROOT/RNTupleModel.hxx>
#include <ROOT/RNTupleWriter.hxx>
using ROOT::Experimental::RNTupleModel;
using ROOT::Experimental::RNTupleWriter;
 
#include <vector>
 
auto model = RNTupleModel::Create();
auto pt = model->MakeField<float>("pt");
auto vec = model->MakeField<std::vector<int>>("vec");
 
// The RNTuple is written to disk when the RNTupleWriter goes out of scope
{
   auto writer = RNTupleWriter::Recreate(std::move(model), "myNTuple", "myFile.root");
   for (int i = 0; i < 100; i++) {
      *pt = static_cast<float>(i);
      *vec = {i, i+1, i+2};
      writer->Fill();
   }
}

Example: create a field with an initial value

#include <ROOT/RNTupleModel.hxx>
using ROOT::Experimental::RNTupleModel;
 
auto model = RNTupleModel::Create();
// pt's initial value is 42.0
auto pt = model->MakeField<float>("pt", 42.0);

Example: create a field with a description

#include <ROOT/RNTupleModel.hxx>
using ROOT::Experimental::RNTupleModel;
 
auto model = RNTupleModel::Create();
auto hadronFlavour = model->MakeField<float>({
   "hadronFlavour", "flavour from hadron ghost clustering"
});

Definition at line 296 of file RNTupleModel.hxx.

◆ operator=()

RNTupleModel & ROOT::Experimental::RNTupleModel::operator= ( const RNTupleModel & )

delete

◆ RegisterSubfield()

void ROOT::Experimental::RNTupleModel::RegisterSubfield ( std::string_view qualifiedFieldName )

Register a subfield so it can be accessed directly from entries belonging to the model.

Because registering a subfield does not fundamentally change the model, previously created entries will not be invalidated, nor modified in any way; a registered subfield is merely an accessor added to the default entry (if present) and any entries created afterwards.

Using models with registered subfields for writing is not allowed. Attempting to do so will result in an exception.

Throws an exception if the provided subfield could not be found in the model.

Definition at line 338 of file RNTupleModel.cxx.

◆ SetDescription()

void ROOT::Experimental::RNTupleModel::SetDescription ( std::string_view description )

Definition at line 515 of file RNTupleModel.cxx.

◆ Unfreeze()

void ROOT::Experimental::RNTupleModel::Unfreeze ( )

Definition at line 496 of file RNTupleModel.cxx.

Friends And Related Symbol Documentation

◆ Internal::GetFieldZeroOfModel

RFieldZero & Internal::GetFieldZeroOfModel ( RNTupleModel & )

friend

◆ Internal::GetProjectedFieldsOfModel

Internal::RProjectedFields & Internal::GetProjectedFieldsOfModel ( RNTupleModel & )

friend

Member Data Documentation

◆ fDefaultEntry

std::unique_ptr<REntry> ROOT::Experimental::RNTupleModel::fDefaultEntry

private

Contains field values corresponding to the created top-level fields, as well as registered subfields.

Definition at line 200 of file RNTupleModel.hxx.

◆ fDescription

std::string ROOT::Experimental::RNTupleModel::fDescription

private

Free text set by the user.

Definition at line 204 of file RNTupleModel.hxx.

◆ fFieldNames

std::unordered_set<std::string> ROOT::Experimental::RNTupleModel::fFieldNames

private

Keeps track of which field names are taken, including projected field names.

Definition at line 202 of file RNTupleModel.hxx.

◆ fFieldZero

std::unique_ptr<RFieldZero> ROOT::Experimental::RNTupleModel::fFieldZero

private

Hierarchy of fields consisting of simple types and collections (sub trees)

Definition at line 198 of file RNTupleModel.hxx.

◆ fIsFrozen

bool ROOT::Experimental::RNTupleModel::fIsFrozen = false

private

Changed by Freeze() / Unfreeze() and by the RUpdater.

Definition at line 215 of file RNTupleModel.hxx.

◆ fModelId

std::uint64_t ROOT::Experimental::RNTupleModel::fModelId = 0

private

Every model has a unique ID to distinguish it from other models.

Entries are linked to models via the ID. Cloned models get a new model ID.

Definition at line 211 of file RNTupleModel.hxx.

◆ fProjectedFields

std::unique_ptr<Internal::RProjectedFields> ROOT::Experimental::RNTupleModel::fProjectedFields

private

The set of projected top-level fields.

Definition at line 206 of file RNTupleModel.hxx.

◆ fRegisteredSubfields

std::unordered_set<std::string> ROOT::Experimental::RNTupleModel::fRegisteredSubfields

private

Keeps track of which subfields have been registered to be included in entries belonging to this model.

Definition at line 208 of file RNTupleModel.hxx.

◆ fSchemaId

std::uint64_t ROOT::Experimental::RNTupleModel::fSchemaId = 0

private

Models have a separate schema ID to remember that the clone of a frozen model still has the same schema.

Definition at line 213 of file RNTupleModel.hxx.

Libraries for ROOT::Experimental::RNTupleModel:

[legend]

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

tree/ntuple/v7/inc/ROOT/RNTupleModel.hxx
tree/ntuple/v7/src/RNTupleModel.cxx

Classes

Public Types

Public Member Functions

Static Public Member Functions

Private Member Functions

Private Attributes

Friends

Member Typedef Documentation

◆ FieldMappingFunc_t

Constructor & Destructor Documentation

◆ RNTupleModel() [1/2]

◆ RNTupleModel() [2/2]

◆ ~RNTupleModel()

Member Function Documentation

◆ AddField()

◆ AddProjectedField()

◆ AddSubfield()

◆ Clone()

◆ Create() [1/2]

◆ Create() [2/2]

◆ CreateBare() [1/2]

◆ CreateBare() [2/2]

◆ CreateBareEntry()

◆ CreateBulk()

◆ CreateEntry()

◆ EnsureNotBare()

◆ EnsureNotFrozen()

◆ EnsureValidFieldName()

◆ EstimateWriteMemoryUsage()

◆ FindField()

◆ Freeze()

◆ GetConstField()

◆ GetConstFieldZero()

◆ GetDefaultEntry() [1/2]

◆ GetDefaultEntry() [2/2]

◆ GetDescription()

◆ GetModelId()

◆ GetMutableField()

◆ GetMutableFieldZero()

◆ GetRegisteredSubfields()

◆ GetSchemaId()

◆ GetToken()

◆ IsBare()

◆ IsFrozen()

◆ MakeField()

◆ operator=()

◆ RegisterSubfield()

◆ SetDescription()

◆ Unfreeze()

Friends And Related Symbol Documentation

◆ Internal::GetFieldZeroOfModel

◆ Internal::GetProjectedFieldsOfModel

Member Data Documentation

◆ fDefaultEntry

◆ fDescription

◆ fFieldNames

◆ fFieldZero

◆ fIsFrozen

◆ fModelId

◆ fProjectedFields

◆ fRegisteredSubfields

◆ fSchemaId