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::MakeCsvDataFrame, 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"
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
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 35 of file RCsvDS.hxx.

Public Member Functions
	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 ()
	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::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::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.

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

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.

Protected Member Functions
std::string	AsString () final

Private Types
using	ColType_t = char

Private Member Functions
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)

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::uint64_t	fDataPos = 0

const char	fDelimiter

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

ULong64_t	fEntryRangesRequested = 0ULL

std::vector< std::string >	fHeaders

const Long64_t	fLinesChunkSize

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

unsigned int	fNSlots = 0U

ULong64_t	fProcessedLines = 0ULL

bool	fReadHeaders = false

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 * >

#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 39 of file RCsvDS.hxx.

Constructor & Destructor Documentation

◆ RCsvDS()

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 331 of file RCsvDS.cxx.

◆ ~RCsvDS()

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

Destructor.

Definition at line 408 of file RCsvDS.cxx.

Member Function Documentation

◆ AsString()

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

finalprotectedvirtual

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 95 of file RCsvDS.cxx.

◆ FillHeaders()

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

private

Definition at line 111 of file RCsvDS.cxx.

◆ FillRecord()

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

private

Definition at line 120 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 413 of file RCsvDS.cxx.

◆ FreeRecords()

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

private

Definition at line 377 of file RCsvDS.cxx.

◆ GenerateHeaders()

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

private

Definition at line 163 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 421 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 171 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 426 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 553 of file RCsvDS.cxx.

◆ GetType()

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

private

Definition at line 484 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 495 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 500 of file RCsvDS.cxx.

◆ InferColTypes()

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

private

Definition at line 222 of file RCsvDS.cxx.

◆ InferType()

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

private

Definition at line 255 of file RCsvDS.cxx.

◆ ParseColumns()

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

private

Definition at line 276 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 287 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 505 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.

Implements ROOT::RDF::RDataSource.

Definition at line 536 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 58 of file RCsvDS.hxx.

◆ fStringEvtValues

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

private

Definition at line 61 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

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()

◆ ~RCsvDS()

Member Function Documentation

◆ AsString()

◆ FillHeaders()

◆ FillRecord()

◆ Finalize()

◆ FreeRecords()

◆ GenerateHeaders()

◆ GetColumnNames()

◆ GetColumnReadersImpl()

◆ GetEntryRanges()

◆ GetLabel()

◆ GetType()

◆ GetTypeName()

◆ HasColumn()

◆ InferColTypes()

◆ InferType()

◆ ParseColumns()

◆ ParseValue()

◆ SetEntry()

◆ SetNSlots()

◆ ValidateColTypes()

Member Data Documentation

◆ fBoolEvtValues

◆ fColAddresses

◆ fColContainingEmpty

◆ fColTypes

◆ fColTypesList

◆ fCsvFile

◆ fDataPos

◆ fDelimiter

◆ fDoubleEvtValues

◆ fEntryRangesRequested

◆ fgColTypeMap

◆ fgDoubleRegex1

◆ fgDoubleRegex2

◆ fgDoubleRegex3

◆ fgFalseRegex

◆ fgIntRegex

◆ fgTrueRegex

◆ fHeaders

◆ fLinesChunkSize

◆ fLong64EvtValues

◆ fNSlots

◆ fProcessedLines

◆ fReadHeaders

◆ fRecords

◆ fStringEvtValues