RDataFrame data source class for reading CSV files.

The RCsvDS class implements a CSV file reader for RDataFrame.

A RDataFrame that reads from a CSV file can be constructed using the factory method ROOT::RDF::FromCSV, which accepts five parameters:

Path to the CSV file.
Boolean that specifies whether the first row of the CSV file contains headers or not (optional, default true). If false, header names will be automatically generated as Col0, Col1, ..., ColN.
Delimiter (optional, default ',').
Chunk size (optional, default is -1 to read all) - number of lines to read at a time
Column Types (optional, default is an empty map). A map with column names as keys and their type (expressed as a single character, see below) as values.

The type of columns that do not appear in the map is inferred from the data. The supported types are:

Integer: stored as a 64-bit long long int; can be specified in the column types map with 'L'.
Floating point number: stored with double precision; specified with 'D'.
Boolean: matches the literals true and false; specified with 'O'.
String: stored as an std::string, matches anything that does not fall into any of the previous types; specified with 'T'.

These are some formatting rules expected by the RCsvDS implementation:

All records must have the same number of fields, in the same order.
Any field may be quoted.
"1997","Ford","E350"
Fields with embedded delimiters (e.g. comma) must be quoted.
1997,Ford,E350,"Super, luxurious truck"

TRangeDynCast
ROOT::Detail::TRangeCast< T, true > TRangeDynCast
TRangeDynCast is an adapter class that allows the typed iteration through a TCollection.
Definition TCollection.h:358
Fields with double-quote characters must be quoted, and each of the embedded double-quote characters must be represented by a pair of double-quote characters.
1997,Ford,E350,"Super, ""luxurious"" truck"
Fields with embedded line breaks are not supported, even when quoted.
1997,Ford,E350,"Go get one now

they are going fast"
Spaces are considered part of a field and are not ignored.
1997, Ford , E350

not same as

1997,Ford,E350

but same as

1997, "Ford" , E350

ROOT::Detail::TRangeCast
Definition TCollection.h:311
If a header row is provided, it must contain column names for each of the fields.
Year,Make,Model

1997,Ford,E350

2000,Mercury,Cougar

The current implementation of RCsvDS reads the entire CSV file content into memory before RDataFrame starts processing it. Therefore, before creating a CSV RDataFrame, it is important to check both how much memory is available and the size of the CSV file.

RCsvDS can handle empty cells and also allows the usage of the special keywords "NaN" and "nan" to indicate nan values. If the column is of type double, these cells are stored internally as nan. Empty cells and explicit nan-s inside columns of type Long64_t/bool are stored as zeros.

Definition at line 45 of file RCsvDS.hxx.

Classes
struct	ROptions
	Options that control how the CSV file is parsed. More...

Public Member Functions
	RCsvDS (const RCsvDS &)=delete

	RCsvDS (RCsvDS &&)=delete

	RCsvDS (std::string_view fileName, bool readHeaders=true, char delimiter=',', Long64_t linesChunkSize=-1LL, std::unordered_map< std::string, char > &&colTypes={})
	Constructor to create a CSV RDataSource for RDataFrame.

	RCsvDS (std::string_view fileName, const ROptions &options)
	Constructor to create a CSV RDataSource for RDataFrame.

	~RCsvDS () final
	Destructor.

void	Finalize () final
	Convenience method called after concluding an event-loop.

const std::vector< std::string > &	GetColumnNames () const final
	Returns a reference to the collection of the dataset's column names.

std::unique_ptr< ROOT::Detail::RDF::RColumnReaderBase >	GetColumnReaders (unsigned int slot, std::string_view colName, const std::type_info &tid) final
	If the other GetColumnReaders overload returns an empty vector, this overload will be called instead.

std::vector< std::pair< ULong64_t, ULong64_t > >	GetEntryRanges () final
	Return ranges of entries to distribute to tasks.

std::string	GetLabel () final
	Return a string representation of the datasource type.

std::size_t	GetNFiles () const final
	Returns the number of files from which the dataset is constructed.

std::string	GetTypeName (std::string_view colName) const final
	Type of a column as a string, e.g.

bool	HasColumn (std::string_view colName) const final
	Checks if the dataset has a certain column.

RCsvDS &	operator= (const RCsvDS &)=delete

RCsvDS &	operator= (RCsvDS &&)=delete

bool	SetEntry (unsigned int slot, ULong64_t entry) final
	Advance the "cursors" returned by GetColumnReaders to the selected entry for a particular slot.

void	SetNSlots (unsigned int nSlots) final
	Inform RDataSource of the number of processing slots (i.e.

Public Member Functions inherited from ROOT::RDF::RDataSource
	RDataSource ()=default

	RDataSource (const RDataSource &)=delete

	RDataSource (RDataSource &&)=delete

virtual	~RDataSource ()=default

virtual void	FinalizeSlot (unsigned int)
	Convenience method called at the end of the data processing associated to a slot.

template<typename T >
std::vector< T ** >	GetColumnReaders (std::string_view columnName)
	Called at most once per column by RDF.

virtual void	Initialize ()
	Convenience method called before starting an event-loop.

virtual void	InitSlot (unsigned int, ULong64_t)
	Convenience method called at the start of the data processing associated to a slot.

RDataSource &	operator= (const RDataSource &)=delete

RDataSource &	operator= (RDataSource &&)=delete

virtual void	SetGlobalEntryRange (std::pair< ULong64_t, ULong64_t > entryRange)
	Restrict processing to a [begin, end) range of entries.

Protected Member Functions
std::string	AsString () final

Protected Member Functions inherited from ROOT::RDF::RDataSource
virtual std::unique_ptr< ROOT::Detail::RDF::RColumnReaderBase >	CreateColumnReader (unsigned int slot, std::string_view col, const std::type_info &tid, TTreeReader *)
	Creates a column reader for the requested column.

virtual ROOT::RDF::RSampleInfo	CreateSampleInfo (unsigned int, const std::unordered_map< std::string, ROOT::RDF::Experimental::RSample * > &) const

virtual std::string	DescribeDataset ()

virtual const std::vector< std::string > &	GetColumnNamesNoDuplicates () const

virtual const std::vector< std::string > &	GetTopLevelFieldNames () const

virtual std::string	GetTypeNameWithOpts (std::string_view colName, bool) const

virtual void	InitializeWithOpts (const std::set< std::string > &)

virtual void	ProcessMT (ROOT::Detail::RDF::RLoopManager &)

virtual void	RunFinalChecks (bool) const

Private Types
using	ColType_t = char

Private Member Functions
void	Construct ()

void	FillHeaders (const std::string &)

void	FillRecord (const std::string &, Record_t &)

void	FreeRecords ()

void	GenerateHeaders (size_t)

std::vector< void * >	GetColumnReadersImpl (std::string_view, const std::type_info &) final
	type-erased vector of pointers to pointers to column values - one per slot

ColType_t	GetType (std::string_view colName) const

void	InferColTypes (std::vector< std::string > &)

void	InferType (const std::string &, unsigned int)

std::vector< std::string >	ParseColumns (const std::string &)

size_t	ParseValue (const std::string &, std::vector< std::string > &, size_t)

bool	Readln (std::string &line)

void	RewindToData ()

void	ValidateColTypes (std::vector< std::string > &) const

Private Attributes
std::vector< std::deque< bool > >	fBoolEvtValues

std::vector< std::vector< void * > >	fColAddresses

std::set< std::string >	fColContainingEmpty

std::unordered_map< std::string, ColType_t >	fColTypes

std::list< ColType_t >	fColTypesList

std::unique_ptr< ROOT::Internal::RRawFile >	fCsvFile

std::int64_t	fDataLineNumber = 0

std::uint64_t	fDataPos = 0

std::vector< std::vector< double > >	fDoubleEvtValues

ULong64_t	fEntryRangesRequested = 0ULL

std::vector< std::string >	fHeaders

std::int64_t	fLineNumber = 0

std::vector< std::vector< Long64_t > >	fLong64EvtValues

std::int64_t	fMaxLineNumber = -1

ROptions	fOptions

ULong64_t	fProcessedLines = 0ULL

std::vector< Record_t >	fRecords

std::vector< std::vector< std::string > >	fStringEvtValues

Static Private Attributes
static const std::unordered_map< ColType_t, std::string >	fgColTypeMap

static const TRegexp	fgDoubleRegex1

static const TRegexp	fgDoubleRegex2

static const TRegexp	fgDoubleRegex3

static const TRegexp	fgFalseRegex

static const TRegexp	fgIntRegex

static const TRegexp	fgTrueRegex

Additional Inherited Members
Protected Types inherited from ROOT::RDF::RDataSource
using	Record_t = std::vector<void *>

Protected Attributes inherited from ROOT::RDF::RDataSource
std::optional< std::pair< ULong64_t, ULong64_t > >	fGlobalEntryRange {}

unsigned int	fNSlots {}

#include <ROOT/RCsvDS.hxx>

Inheritance diagram for ROOT::RDF::RCsvDS:

[legend]

Member Typedef Documentation

◆ ColType_t

using ROOT::RDF::RCsvDS::ColType_t = char

private

Definition at line 75 of file RCsvDS.hxx.

Constructor & Destructor Documentation

◆ RCsvDS() [1/4]

ROOT::RDF::RCsvDS::RCsvDS	(	std::string_view	fileName,
		const ROptions &	options )

Constructor to create a CSV RDataSource for RDataFrame.

Parameters

[in]	fileName	Path or URL of the CSV file.
[in]	options	File parsing settings

Definition at line 434 of file RCsvDS.cxx.

◆ RCsvDS() [2/4]

ROOT::RDF::RCsvDS::RCsvDS	(	std::string_view	fileName,
		bool	readHeaders = true,
		char	delimiter = ',',
		Long64_t	linesChunkSize = -1LL,
		std::unordered_map< std::string, char > &&	colTypes = {} )

Constructor to create a CSV RDataSource for RDataFrame.

Parameters

[in]	fileName	Path or URL of the CSV file.
[in]	readHeaders	`true` if the CSV file contains headers as first row, `false` otherwise (default `true`).
[in]	delimiter	Delimiter character (default ',').
[in]	linesChunkSize	bunch of lines to read, use -1 to read all
[in]	colTypes	Allows users to manually specify column types. Accepts an unordered map with keys being column names, values being type specifiers ('O' for boolean, 'D' for double, 'L' for Long64_t, 'T' for std::string)

Definition at line 452 of file RCsvDS.cxx.

◆ RCsvDS() [3/4]

ROOT::RDF::RCsvDS::RCsvDS ( const RCsvDS & )

delete

◆ RCsvDS() [4/4]

ROOT::RDF::RCsvDS::RCsvDS ( RCsvDS && )

delete

◆ ~RCsvDS()

ROOT::RDF::RCsvDS::~RCsvDS ( )

final

Destructor.

Definition at line 494 of file RCsvDS.cxx.

Member Function Documentation

◆ AsString()

std::string ROOT::RDF::RCsvDS::AsString ( )

finalprotectedvirtual

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 98 of file RCsvDS.cxx.

◆ Construct()

void ROOT::RDF::RCsvDS::Construct ( )

private

Definition at line 369 of file RCsvDS.cxx.

◆ FillHeaders()

void ROOT::RDF::RCsvDS::FillHeaders ( const std::string & line )

private

Definition at line 165 of file RCsvDS.cxx.

◆ FillRecord()

void ROOT::RDF::RCsvDS::FillRecord	(	const std::string &	line,
		Record_t &	record )

private

Definition at line 185 of file RCsvDS.cxx.

◆ Finalize()

void ROOT::RDF::RCsvDS::Finalize ( )

finalvirtual

Convenience method called after concluding an event-loop.

See Initialize for more details.

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 499 of file RCsvDS.cxx.

◆ FreeRecords()

void ROOT::RDF::RCsvDS::FreeRecords ( )

private

Definition at line 463 of file RCsvDS.cxx.

◆ GenerateHeaders()

void ROOT::RDF::RCsvDS::GenerateHeaders ( size_t size )

private

Definition at line 228 of file RCsvDS.cxx.

◆ GetColumnNames()

const std::vector< std::string > & ROOT::RDF::RCsvDS::GetColumnNames ( ) const

finalvirtual

Returns a reference to the collection of the dataset's column names.

Implements ROOT::RDF::RDataSource.

Definition at line 507 of file RCsvDS.cxx.

◆ GetColumnReaders()

std::unique_ptr< ROOT::Detail::RDF::RColumnReaderBase > ROOT::RDF::RCsvDS::GetColumnReaders	(	unsigned int	,
		std::string_view	,
		const std::type_info &	)

finalvirtual

If the other GetColumnReaders overload returns an empty vector, this overload will be called instead.

Parameters

[in]	slot	The data processing slot that needs to be considered
[in]	name	The name of the column for which a column reader needs to be returned
[in]	tid	A type_info At least one of the two must return a non-empty/non-null value.

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 663 of file RCsvDS.cxx.

◆ GetColumnReadersImpl()

std::vector< void * > ROOT::RDF::RCsvDS::GetColumnReadersImpl	(	std::string_view	name,
		const std::type_info &	)

finalprivatevirtual

type-erased vector of pointers to pointers to column values - one per slot

Implements ROOT::RDF::RDataSource.

Definition at line 246 of file RCsvDS.cxx.

◆ GetEntryRanges()

std::vector< std::pair< ULong64_t, ULong64_t > > ROOT::RDF::RCsvDS::GetEntryRanges ( )

finalvirtual

Return ranges of entries to distribute to tasks.

They are required to be contiguous intervals with no entries skipped. Supposing a dataset with nEntries, the intervals must start at 0 and end at nEntries, e.g. [0-5],[5-10] for 10 entries. This function will be invoked repeatedly by RDataFrame as it needs additional entries to process. The same entry range should not be returned more than once. Returning an empty collection of ranges signals to RDataFrame that the processing can stop.

Implements ROOT::RDF::RDataSource.

Definition at line 512 of file RCsvDS.cxx.

◆ GetLabel()

std::string ROOT::RDF::RCsvDS::GetLabel ( )

finalvirtual

Return a string representation of the datasource type.

The returned string will be used by ROOT::RDF::SaveGraph() to represent the datasource in the visualization of the computation graph. Concrete datasources can override the default implementation.

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 639 of file RCsvDS.cxx.

◆ GetNFiles()

std::size_t ROOT::RDF::RCsvDS::GetNFiles ( ) const

inlinefinalvirtual

Returns the number of files from which the dataset is constructed.

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 133 of file RCsvDS.hxx.

◆ GetType()

RCsvDS::ColType_t ROOT::RDF::RCsvDS::GetType ( std::string_view colName ) const

private

Definition at line 570 of file RCsvDS.cxx.

◆ GetTypeName()

std::string ROOT::RDF::RCsvDS::GetTypeName ( std::string_view colName ) const

finalvirtual

Type of a column as a string, e.g.

GetTypeName("x") == "double". Required for jitting e.g. df.Filter("x>0").

Parameters

[in] colName The name of the column

Implements ROOT::RDF::RDataSource.

Definition at line 581 of file RCsvDS.cxx.

◆ HasColumn()

bool ROOT::RDF::RCsvDS::HasColumn ( std::string_view colName ) const

finalvirtual

Checks if the dataset has a certain column.

Parameters

[in] colName The name of the column

Implements ROOT::RDF::RDataSource.

Definition at line 586 of file RCsvDS.cxx.

◆ InferColTypes()

void ROOT::RDF::RCsvDS::InferColTypes ( std::vector< std::string > & columns )

private

Definition at line 270 of file RCsvDS.cxx.

◆ InferType()

void ROOT::RDF::RCsvDS::InferType	(	const std::string &	col,
		unsigned int	idxCol )

private

Definition at line 303 of file RCsvDS.cxx.

◆ operator=() [1/2]

RCsvDS & ROOT::RDF::RCsvDS::operator= ( const RCsvDS & )

delete

◆ operator=() [2/2]

RCsvDS & ROOT::RDF::RCsvDS::operator= ( RCsvDS && )

delete

◆ ParseColumns()

std::vector< std::string > ROOT::RDF::RCsvDS::ParseColumns ( const std::string & line )

private

Definition at line 324 of file RCsvDS.cxx.

◆ ParseValue()

size_t ROOT::RDF::RCsvDS::ParseValue	(	const std::string &	line,
		std::vector< std::string > &	columns,
		size_t	i )

private

Definition at line 335 of file RCsvDS.cxx.

◆ Readln()

bool ROOT::RDF::RCsvDS::Readln ( std::string & line )

private

Definition at line 114 of file RCsvDS.cxx.

◆ RewindToData()

void ROOT::RDF::RCsvDS::RewindToData ( )

private

Definition at line 159 of file RCsvDS.cxx.

◆ SetEntry()

bool ROOT::RDF::RCsvDS::SetEntry	(	unsigned int	slot,
		ULong64_t	entry )

finalvirtual

Advance the "cursors" returned by GetColumnReaders to the selected entry for a particular slot.

Parameters

[in]	slot	The data processing slot that needs to be considered
[in]	entry	The entry which needs to be pointed to by the reader pointers Slots are adopted to accommodate parallel data processing. Different workers will loop over different ranges and will be labelled by different "slot" values. Returns true if the entry has to be processed, false otherwise.

Implements ROOT::RDF::RDataSource.

Definition at line 591 of file RCsvDS.cxx.

◆ SetNSlots()

void ROOT::RDF::RCsvDS::SetNSlots ( unsigned int nSlots )

finalvirtual

Inform RDataSource of the number of processing slots (i.e.

worker threads) used by the associated RDataFrame. Slots numbers are used to simplify parallel execution: RDataFrame guarantees that different threads will always pass different slot values when calling methods concurrently.

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 622 of file RCsvDS.cxx.

◆ ValidateColTypes()

void ROOT::RDF::RCsvDS::ValidateColTypes ( std::vector< std::string > & columns ) const

std::vector<Record_t> ROOT::RDF::RCsvDS::fRecords

private

Definition at line 94 of file RCsvDS.hxx.

◆ fStringEvtValues

std::vector<std::vector<std::string> > ROOT::RDF::RCsvDS::fStringEvtValues

private

Definition at line 97 of file RCsvDS.hxx.

Libraries for ROOT::RDF::RCsvDS:

[legend]

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

tree/dataframe/inc/ROOT/RCsvDS.hxx
tree/dataframe/src/RCsvDS.cxx

Classes

Public Member Functions

Protected Member Functions

Private Types

Private Member Functions

Private Attributes

Static Private Attributes

Additional Inherited Members

Member Typedef Documentation

◆ ColType_t

Constructor & Destructor Documentation

◆ RCsvDS() [1/4]

◆ RCsvDS() [2/4]

◆ RCsvDS() [3/4]

◆ RCsvDS() [4/4]

◆ ~RCsvDS()

Member Function Documentation

◆ AsString()

◆ Construct()

◆ FillHeaders()

◆ FillRecord()

◆ Finalize()

◆ FreeRecords()

◆ GenerateHeaders()

◆ GetColumnNames()

◆ GetColumnReaders()

◆ GetColumnReadersImpl()

◆ GetEntryRanges()

◆ GetLabel()

◆ GetNFiles()

◆ GetType()

◆ GetTypeName()

◆ HasColumn()

◆ InferColTypes()

◆ InferType()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ ParseColumns()

◆ ParseValue()

◆ Readln()

◆ RewindToData()

◆ SetEntry()

◆ SetNSlots()

◆ ValidateColTypes()

Member Data Documentation

◆ fBoolEvtValues

◆ fColAddresses

◆ fColContainingEmpty

◆ fColTypes

◆ fColTypesList

◆ fCsvFile

◆ fDataLineNumber

◆ fDataPos

◆ fDoubleEvtValues

◆ fEntryRangesRequested

◆ fgColTypeMap

◆ fgDoubleRegex1

◆ fgDoubleRegex2

◆ fgDoubleRegex3

◆ fgFalseRegex

◆ fgIntRegex

◆ fgTrueRegex

◆ fHeaders

◆ fLineNumber

◆ fLong64EvtValues

◆ fMaxLineNumber

◆ fOptions

◆ fProcessedLines

◆ fRecords

◆ fStringEvtValues