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Reference Guide
ROOT::Experimental::RNTupleDescriptor Class Reference


The on-storage meta-data of an ntuple

Represents the on-disk (on storage) information about an ntuple. The meta-data consists of a header and one or several footers. The header carries the ntuple schema, i.e. the fields and the associated columns and their relationships. The footer(s) carry information about one or several clusters. For every cluster, a footer stores its location and size, and for every column the range of element indexes as well as a list of pages and page locations.

The descriptor provide machine-independent (de-)serialization of headers and footers, and it provides lookup routines for ntuple objects (pages, clusters, ...). It is supposed to be usable by all RPageStorage implementations.

The serialization does not use standard ROOT streamers in order to not let it depend on libCore. The serialization uses the concept of frames: header, footer, and substructures have a preamble with version numbers and the size of the writte struct. This allows for forward and backward compatibility when the meta-data evolves.

Definition at line 272 of file RNTupleDescriptor.hxx.

Public Member Functions

 RNTupleDescriptor ()=default
 
 RNTupleDescriptor (const RNTupleDescriptor &other)=delete
 
 RNTupleDescriptor (RNTupleDescriptor &&other)=default
 
DescriptorId_t FindClusterId (DescriptorId_t columnId, NTupleSize_t index) const
 
DescriptorId_t FindColumnId (DescriptorId_t fieldId, std::uint32_t columnIndex) const
 
DescriptorId_t FindFieldId (std::string_view fieldName, DescriptorId_t parentId) const
 
DescriptorId_t FindFieldId (std::string_view fieldName) const
 Searches for a top-level field. More...
 
std::unique_ptr< RNTupleModelGenerateModel () const
 Re-create the C++ model from the stored meta-data. More...
 
std::string GetAuthor () const
 
const RClusterDescriptorGetClusterDescriptor (DescriptorId_t clusterId) const
 
const RColumnDescriptorGetColumnDescriptor (DescriptorId_t columnId) const
 
std::string GetCustodian () const
 
std::string GetDescription () const
 
const RFieldDescriptorGetFieldDescriptor (DescriptorId_t fieldId) const
 
RNTupleUuid GetGroupUuid () const
 
std::string GetName () const
 
std::size_t GetNClusters () const
 
std::size_t GetNColumns () const
 
NTupleSize_t GetNElements (DescriptorId_t columnId) const
 
NTupleSize_t GetNEntries () const
 
std::size_t GetNFields () const
 
RNTupleUuid GetOwnUuid () const
 
std::chrono::system_clock::time_point GetTimeStampData () const
 
std::chrono::system_clock::time_point GetTimeStampWritten () const
 
RNTupleVersion GetVersion () const
 
RNTupleDescriptoroperator= (const RNTupleDescriptor &other)=delete
 
RNTupleDescriptoroperator= (RNTupleDescriptor &&other)=default
 
bool operator== (const RNTupleDescriptor &other) const
 
void PrintInfo (std::ostream &output) const
 
std::uint32_t SerializeFooter (void *buffer) const
 Serializes cluster meta data. Returns the number of bytes and fills buffer if it is not nullptr. More...
 
std::uint32_t SerializeHeader (void *buffer) const
 We deliberately do not use ROOT's built-in serialization in order to allow for use of RNTuple's without libCore Serializes the global ntuple information as well as the column and field schemata Returns the number of bytes and fills buffer if it is not nullptr. More...
 

Static Public Member Functions

static void LocateMetadata (const void *postscript, std::uint32_t &szHeader, std::uint32_t &szFooter)
 Given kNBytesPostscript bytes, extract the header and footer lengths in bytes. More...
 

Static Public Attributes

static constexpr std::uint16_t kFrameVersionCurrent = 0
 In order to handle changes to the serialization routine in future ntuple versions. More...
 
static constexpr std::uint16_t kFrameVersionMin = 0
 
static constexpr unsigned int kNBytesPostscript = 16
 The last few bytes after the footer store the length of footer and header. More...
 
static constexpr unsigned int kNBytesPreamble = 8
 The preamble is sufficient to get the length of the header. More...
 

Private Attributes

std::string fAuthor
 The origin of the data. More...
 
std::unordered_map< DescriptorId_t, RClusterDescriptorfClusterDescriptors
 May contain only a subset of all the available clusters, e.g. More...
 
std::unordered_map< DescriptorId_t, RColumnDescriptorfColumnDescriptors
 
std::string fCustodian
 The current responsible for storing the data. More...
 
std::string fDescription
 Free text from the user. More...
 
std::unordered_map< DescriptorId_t, RFieldDescriptorfFieldDescriptors
 
RNTupleUuid fGroupUuid
 Column sets that are created as derived sets from existing NTuples share the same group id. More...
 
std::string fName
 The ntuple name needs to be unique in a given storage location (file) More...
 
RNTupleUuid fOwnUuid
 Every NTuple gets a unique identifier. More...
 
std::chrono::system_clock::time_point fTimeStampData
 The time stamp of the ntuple data (immutable) More...
 
std::chrono::system_clock::time_point fTimeStampWritten
 The time stamp of writing the data to storage, which gets updated when re-written. More...
 
RNTupleVersion fVersion
 The version evolves with the ntuple summary meta-data. More...
 

Friends

class RNTupleDescriptorBuilder
 

#include <ROOT/RNTupleDescriptor.hxx>

Constructor & Destructor Documentation

◆ RNTupleDescriptor() [1/3]

ROOT::Experimental::RNTupleDescriptor::RNTupleDescriptor ( )
default

◆ RNTupleDescriptor() [2/3]

ROOT::Experimental::RNTupleDescriptor::RNTupleDescriptor ( const RNTupleDescriptor other)
delete

◆ RNTupleDescriptor() [3/3]

ROOT::Experimental::RNTupleDescriptor::RNTupleDescriptor ( RNTupleDescriptor &&  other)
default

Member Function Documentation

◆ FindClusterId()

ROOT::Experimental::DescriptorId_t ROOT::Experimental::RNTupleDescriptor::FindClusterId ( DescriptorId_t  columnId,
NTupleSize_t  index 
) const

Definition at line 685 of file RNTupleDescriptor.cxx.

◆ FindColumnId()

ROOT::Experimental::DescriptorId_t ROOT::Experimental::RNTupleDescriptor::FindColumnId ( DescriptorId_t  fieldId,
std::uint32_t  columnIndex 
) const

Definition at line 674 of file RNTupleDescriptor.cxx.

◆ FindFieldId() [1/2]

ROOT::Experimental::DescriptorId_t ROOT::Experimental::RNTupleDescriptor::FindFieldId ( std::string_view  fieldName,
DescriptorId_t  parentId 
) const

Definition at line 649 of file RNTupleDescriptor.cxx.

◆ FindFieldId() [2/2]

ROOT::Experimental::DescriptorId_t ROOT::Experimental::RNTupleDescriptor::FindFieldId ( std::string_view  fieldName) const

Searches for a top-level field.

Definition at line 666 of file RNTupleDescriptor.cxx.

◆ GenerateModel()

std::unique_ptr< ROOT::Experimental::RNTupleModel > ROOT::Experimental::RNTupleDescriptor::GenerateModel ( ) const

Re-create the C++ model from the stored meta-data.

Definition at line 697 of file RNTupleDescriptor.cxx.

◆ GetAuthor()

std::string ROOT::Experimental::RNTupleDescriptor::GetAuthor ( ) const
inline

Definition at line 339 of file RNTupleDescriptor.hxx.

◆ GetClusterDescriptor()

const RClusterDescriptor& ROOT::Experimental::RNTupleDescriptor::GetClusterDescriptor ( DescriptorId_t  clusterId) const
inline

Definition at line 334 of file RNTupleDescriptor.hxx.

◆ GetColumnDescriptor()

const RColumnDescriptor& ROOT::Experimental::RNTupleDescriptor::GetColumnDescriptor ( DescriptorId_t  columnId) const
inline

Definition at line 331 of file RNTupleDescriptor.hxx.

◆ GetCustodian()

std::string ROOT::Experimental::RNTupleDescriptor::GetCustodian ( ) const
inline

Definition at line 340 of file RNTupleDescriptor.hxx.

◆ GetDescription()

std::string ROOT::Experimental::RNTupleDescriptor::GetDescription ( ) const
inline

Definition at line 338 of file RNTupleDescriptor.hxx.

◆ GetFieldDescriptor()

const RFieldDescriptor& ROOT::Experimental::RNTupleDescriptor::GetFieldDescriptor ( DescriptorId_t  fieldId) const
inline

Definition at line 330 of file RNTupleDescriptor.hxx.

◆ GetGroupUuid()

RNTupleUuid ROOT::Experimental::RNTupleDescriptor::GetGroupUuid ( ) const
inline

Definition at line 345 of file RNTupleDescriptor.hxx.

◆ GetName()

std::string ROOT::Experimental::RNTupleDescriptor::GetName ( ) const
inline

Definition at line 337 of file RNTupleDescriptor.hxx.

◆ GetNClusters()

std::size_t ROOT::Experimental::RNTupleDescriptor::GetNClusters ( ) const
inline

Definition at line 349 of file RNTupleDescriptor.hxx.

◆ GetNColumns()

std::size_t ROOT::Experimental::RNTupleDescriptor::GetNColumns ( ) const
inline

Definition at line 348 of file RNTupleDescriptor.hxx.

◆ GetNElements()

ROOT::Experimental::NTupleSize_t ROOT::Experimental::RNTupleDescriptor::GetNElements ( DescriptorId_t  columnId) const

Definition at line 638 of file RNTupleDescriptor.cxx.

◆ GetNEntries()

ROOT::Experimental::NTupleSize_t ROOT::Experimental::RNTupleDescriptor::GetNEntries ( ) const

Definition at line 629 of file RNTupleDescriptor.cxx.

◆ GetNFields()

std::size_t ROOT::Experimental::RNTupleDescriptor::GetNFields ( ) const
inline

Definition at line 347 of file RNTupleDescriptor.hxx.

◆ GetOwnUuid()

RNTupleUuid ROOT::Experimental::RNTupleDescriptor::GetOwnUuid ( ) const
inline

Definition at line 344 of file RNTupleDescriptor.hxx.

◆ GetTimeStampData()

std::chrono::system_clock::time_point ROOT::Experimental::RNTupleDescriptor::GetTimeStampData ( ) const
inline

Definition at line 341 of file RNTupleDescriptor.hxx.

◆ GetTimeStampWritten()

std::chrono::system_clock::time_point ROOT::Experimental::RNTupleDescriptor::GetTimeStampWritten ( ) const
inline

Definition at line 342 of file RNTupleDescriptor.hxx.

◆ GetVersion()

RNTupleVersion ROOT::Experimental::RNTupleDescriptor::GetVersion ( ) const
inline

Definition at line 343 of file RNTupleDescriptor.hxx.

◆ LocateMetadata()

void ROOT::Experimental::RNTupleDescriptor::LocateMetadata ( const void postscript,
std::uint32_t &  szHeader,
std::uint32_t &  szFooter 
)
static

Given kNBytesPostscript bytes, extract the header and footer lengths in bytes.

Definition at line 617 of file RNTupleDescriptor.cxx.

◆ operator=() [1/2]

RNTupleDescriptor& ROOT::Experimental::RNTupleDescriptor::operator= ( const RNTupleDescriptor other)
delete

◆ operator=() [2/2]

RNTupleDescriptor& ROOT::Experimental::RNTupleDescriptor::operator= ( RNTupleDescriptor &&  other)
default

◆ operator==()

bool ROOT::Experimental::RNTupleDescriptor::operator== ( const RNTupleDescriptor other) const

Definition at line 517 of file RNTupleDescriptor.cxx.

◆ PrintInfo()

void ROOT::Experimental::RNTupleDescriptor::PrintInfo ( std::ostream &  output) const

Definition at line 97 of file RNTupleDescriptorFmt.cxx.

◆ SerializeFooter()

std::uint32_t ROOT::Experimental::RNTupleDescriptor::SerializeFooter ( void buffer) const

Serializes cluster meta data. Returns the number of bytes and fills buffer if it is not nullptr.

Definition at line 569 of file RNTupleDescriptor.cxx.

◆ SerializeHeader()

std::uint32_t ROOT::Experimental::RNTupleDescriptor::SerializeHeader ( void buffer) const

We deliberately do not use ROOT's built-in serialization in order to allow for use of RNTuple's without libCore Serializes the global ntuple information as well as the column and field schemata Returns the number of bytes and fills buffer if it is not nullptr.

TODO(jblomer): instead of runtime testing for nullptr, there should be a template for the case where only the size of the buffer is required.

Definition at line 533 of file RNTupleDescriptor.cxx.

Friends And Related Function Documentation

◆ RNTupleDescriptorBuilder

friend class RNTupleDescriptorBuilder
friend

Definition at line 273 of file RNTupleDescriptor.hxx.

Member Data Documentation

◆ fAuthor

std::string ROOT::Experimental::RNTupleDescriptor::fAuthor
private

The origin of the data.

Definition at line 281 of file RNTupleDescriptor.hxx.

◆ fClusterDescriptors

std::unordered_map<DescriptorId_t, RClusterDescriptor> ROOT::Experimental::RNTupleDescriptor::fClusterDescriptors
private

May contain only a subset of all the available clusters, e.g.

the clusters of the current file from a chain of files

Definition at line 300 of file RNTupleDescriptor.hxx.

◆ fColumnDescriptors

std::unordered_map<DescriptorId_t, RColumnDescriptor> ROOT::Experimental::RNTupleDescriptor::fColumnDescriptors
private

Definition at line 297 of file RNTupleDescriptor.hxx.

◆ fCustodian

std::string ROOT::Experimental::RNTupleDescriptor::fCustodian
private

The current responsible for storing the data.

Definition at line 283 of file RNTupleDescriptor.hxx.

◆ fDescription

std::string ROOT::Experimental::RNTupleDescriptor::fDescription
private

Free text from the user.

Definition at line 279 of file RNTupleDescriptor.hxx.

◆ fFieldDescriptors

std::unordered_map<DescriptorId_t, RFieldDescriptor> ROOT::Experimental::RNTupleDescriptor::fFieldDescriptors
private

Definition at line 296 of file RNTupleDescriptor.hxx.

◆ fGroupUuid

RNTupleUuid ROOT::Experimental::RNTupleDescriptor::fGroupUuid
private

Column sets that are created as derived sets from existing NTuples share the same group id.

NTuples in the same group have the same number of entries and are supposed to contain associated data.

Definition at line 294 of file RNTupleDescriptor.hxx.

◆ fName

std::string ROOT::Experimental::RNTupleDescriptor::fName
private

The ntuple name needs to be unique in a given storage location (file)

Definition at line 277 of file RNTupleDescriptor.hxx.

◆ fOwnUuid

RNTupleUuid ROOT::Experimental::RNTupleDescriptor::fOwnUuid
private

Every NTuple gets a unique identifier.

Definition at line 291 of file RNTupleDescriptor.hxx.

◆ fTimeStampData

std::chrono::system_clock::time_point ROOT::Experimental::RNTupleDescriptor::fTimeStampData
private

The time stamp of the ntuple data (immutable)

Definition at line 285 of file RNTupleDescriptor.hxx.

◆ fTimeStampWritten

std::chrono::system_clock::time_point ROOT::Experimental::RNTupleDescriptor::fTimeStampWritten
private

The time stamp of writing the data to storage, which gets updated when re-written.

Definition at line 287 of file RNTupleDescriptor.hxx.

◆ fVersion

RNTupleVersion ROOT::Experimental::RNTupleDescriptor::fVersion
private

The version evolves with the ntuple summary meta-data.

Definition at line 289 of file RNTupleDescriptor.hxx.

◆ kFrameVersionCurrent

constexpr std::uint16_t ROOT::Experimental::RNTupleDescriptor::kFrameVersionCurrent = 0
static

In order to handle changes to the serialization routine in future ntuple versions.

Definition at line 304 of file RNTupleDescriptor.hxx.

◆ kFrameVersionMin

constexpr std::uint16_t ROOT::Experimental::RNTupleDescriptor::kFrameVersionMin = 0
static

Definition at line 305 of file RNTupleDescriptor.hxx.

◆ kNBytesPostscript

constexpr unsigned int ROOT::Experimental::RNTupleDescriptor::kNBytesPostscript = 16
static

The last few bytes after the footer store the length of footer and header.

Definition at line 309 of file RNTupleDescriptor.hxx.

◆ kNBytesPreamble

constexpr unsigned int ROOT::Experimental::RNTupleDescriptor::kNBytesPreamble = 8
static

The preamble is sufficient to get the length of the header.

Definition at line 307 of file RNTupleDescriptor.hxx.


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