In order to store columnar datasets, ROOT provides the TTree, TChain, TNtuple and TNtupleD classes.

The TTree class represents a columnar dataset. Any C++ type can be stored in the columns. The TTree has allowed to store about 1 EB of data coming from the LHC alone: it is demonstrated to scale and it's battle tested. It has been optimized during the years to reduce dataset sizes on disk and to deliver excellent runtime performance. It allows to access only part of the columns of the datasets, too. The TNtuple and TNtupleD classes are specialisations of the TTree class which can only hold single precision and double precision floating-point numbers respectively; The TChain is a collection of TTrees, which can be located also in different files.

Files
file	InternalTreeUtils.hxx

Namespaces
namespace	ROOT::Internal::TreeUtils
	Namespace hosting functions and classes to retrieve tree information for internal use.

Classes
struct	ROOT::Internal::TreeUtils::RFriendInfo
	Information about friend trees of a certain TTree or TChain object. More...

class	TBasket
	Manages buffers for branches of a Tree. More...

class	TBasketSQL
	Implement TBasket for a SQL backend. More...

class	TBranch
	A TTree is a list of TBranches. More...

class	TBranchClones
	A Branch for the case of an array of clone objects. More...

class	TBranchElement
	A Branch for the case of an object. More...

class	TBranchObject
	A Branch for the case of an object. More...

class	TBranchRef
	A branch containing and managing a TRefTable for TRef autoloading. More...

class	TBranchSTL
	A Branch handling STL collection of pointers (vectors, lists, queues, sets and multisets) while storing them in split mode. More...

class	TBufferSQL
	Implement TBuffer for a SQL backend. More...

class	TChain
	A chain is a collection of files containing TTree objects. More...

class	TChainElement
	A TChainElement describes a component of a TChain. More...

class	TCollectionMethodBrowsable
	TCollectionMethodBrowsable extends TCollectionPropertyBrowsable by showing all methods of the collection itself. More...

class	TCollectionPropertyBrowsable
	A tiny browser helper object (and its generator) for adding a virtual (as in "not actually part of the class", not in C++ virtual) "@size()" method to a collection. More...

class	TCut
	A specialized string object used for TTree selections. More...

class	TEntryList
	A List of entry numbers in a TTree or TChain. More...

class	TEntryListArray
	A list of entries and subentries in a TTree or TChain. More...

class	TEntryListBlock
	Used by TEntryList to store the entry numbers. More...

class	TEntryListFromFile
	Manages entry lists from different files, when they are not loaded in memory at the same time. More...

class	TEventList
	A TEventList object is a list of selected events (entries) in a TTree. More...

class	TFriendElement
	A TFriendElement TF describes a TTree object TF in a file. More...

class	ROOT::TIOFeatures
	`TIOFeatures` provides the end-user with the ability to change the IO behavior of data written via a `TTree`. More...

class	TLeaf
	A TLeaf describes individual elements of a TBranch See TBranch structure in TTree. More...

class	TLeafB
	A TLeaf for an 8 bit Integer data type. More...

class	TLeafC
	A TLeaf for a variable length string. More...

class	TLeafD
	A TLeaf for a 64 bit floating point data type. More...

class	TLeafD32
	A TLeaf for a 24 bit truncated floating point data type. More...

class	TLeafElement
	A TLeaf for the general case when using the branches created via a TStreamerInfo (i.e. More...

class	TLeafF
	A TLeaf for a 32 bit floating point data type. More...

class	TLeafF16
	A TLeaf for a 24 bit truncated floating point data type. More...

class	TLeafG
	A TLeaf for a 64 bit Integer data type. More...

class	TLeafI
	A TLeaf for an Integer data type. More...

class	TLeafL
	A TLeaf for a 64 bit Integer data type. More...

class	TLeafO
	A TLeaf for a bool data type. More...

class	TLeafObject
	A TLeaf for a general object derived from TObject. More...

class	TLeafS
	A TLeaf for a 16 bit Integer data type. More...

class	TMethodBrowsable
	This helper object allows the browsing of methods of objects stored in branches. More...

class	TNonSplitBrowsable
	Allows a TBrowser to browse non-split branches as if they were split. More...

class	TNtuple
	A simple TTree restricted to a list of float variables only. More...

class	TNtupleD
	A simple TTree restricted to a list of double variables only. More...

class	TQueryResult
	A container class for query results. More...

class	TreeUtils
	Different standalone functions to work with trees and tuples, not reqiuired to be a member of any class. More...

class	TSelector
	A TSelector object is used by the TTree::Draw, TTree::Scan, TTree::Process to navigate in a TTree and make selections. More...

class	TSelectorList
	A TList derived class that makes sure that objects added to it are not linked to the currently open file (like histograms, eventlists and trees). More...

class	TSelectorScalar
	Named scalar type, based on Long64_t, streamable, storable and mergeable. More...

class	TTree
	A TTree represents a columnar dataset. More...

class	TTreeCache
	A cache to speed-up the reading of ROOT datasets. More...

class	TTreeCacheUnzip
	A TTreeCache which exploits parallelized decompression of its own content. More...

class	TTreeCloner
	Class implementing or helping the various TTree cloning method. More...

class	TTreeResult
	Class defining interface to a TTree query result with the same interface as for SQL databases. More...

class	TTreeRow
	Class defining interface to a row of a TTree query result. More...

class	TTreeSQL
	A TTree object is a list of TBranch. More...

class	TVirtualBranchBrowsable
	TVirtualBranchBrowsable is a base class (not really abstract, but useless by itself) for helper objects that extend TBranch's browsing support. More...

class	TVirtualIndex
	Abstract interface for Tree Index. More...

class	TVirtualTreePlayer
	Abstract base class defining the interface for the plugins that implement Draw, Scan, Process, MakeProxy, etc. More...

Functions
std::vector< std::string >	ROOT::Internal::TreeUtils::GetFileNamesFromTree (const TTree &tree)
	Get and store the file names associated with the input tree. More...

RFriendInfo	ROOT::Internal::TreeUtils::GetFriendInfo (const TTree &tree)
	Get and store the names, aliases and file names of the direct friends of the tree. More...

std::vector< std::string >	ROOT::Internal::TreeUtils::GetTreeFullPaths (const TTree &tree)
	Retrieve the full path(s) to a TTree or the trees in a TChain. More...

Function Documentation

◆ GetFileNamesFromTree()

std::vector< std::string > ROOT::Internal::TreeUtils::GetFileNamesFromTree ( const TTree & tree )

Get and store the file names associated with the input tree.

Parameters

[in] tree The tree from which friends information will be gathered.

Exceptions

std::runtime_error If no files could be associated with the input tree.

Definition at line 87 of file InternalTreeUtils.cxx.

◆ GetFriendInfo()

RFriendInfo ROOT::Internal::TreeUtils::GetFriendInfo ( const TTree & tree )

Get and store the names, aliases and file names of the direct friends of the tree.

Parameters

[in] tree The tree from which friends information will be gathered.

Exceptions

std::runtime_error If the input tree has a list of friends, but any of them could not be associated with any file.

Calls TTree::GetListOfFriends and parses its result for the names, aliases and file names, with different methodologies depending on whether the parameter is a TTree or a TChain.

Note: This function only retrieves information about direct friends of the input tree. It will not recurse through friends of friends and does not take into account circular references in the list of friends of the input tree.

Returns: An RFriendInfo struct, containing the information parsed from the list of friends. The struct will contain three vectors, which elements at position i represent the i-th friend of the input tree. If this friend is a TTree, the i-th element of each of the three vectors will contain respectively:

A pair with the name and alias of the tree (the alias might not be present, in which case it will be just an empty string).
A vector with a single string representing the path to current file where the tree is stored.
An empty vector.

If the i-th friend is a TChain instead, the i-th element of each of the three vectors will contain respectively:

A pair with the name and alias of the chain (if present, both might be empty strings).
A vector with all the paths to the files contained in the chain.
A vector with all the the names of the trees making up the chain, associated with the file names of the previous vector.

Definition at line 155 of file InternalTreeUtils.cxx.

◆ GetTreeFullPaths()

std::vector< std::string > ROOT::Internal::TreeUtils::GetTreeFullPaths ( const TTree & tree )

Retrieve the full path(s) to a TTree or the trees in a TChain.

Parameters

[in] tree The tree or chain from which the paths will be retrieved.

Exceptions

std::runtime_error If the input tree is a TChain but no files could be found associated with it.

Returns: If the input argument is a TChain, returns a vector of strings with the name of the tree of each file in the chain. If the input argument is a TTree, returns a vector with a single element that is the full path of the tree in the file (e.g. the name of the tree itself or the path with the directories inside the file). Finally, the function returns a vector with just the name of the tree if it couldn't do any better.

Definition at line 247 of file InternalTreeUtils.cxx.

Files

Namespaces

Classes

Functions

Function Documentation

◆ GetFileNamesFromTree()

◆ GetFriendInfo()

◆ GetTreeFullPaths()