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Reference Guide
ROOT::RDF::RCsvDS Class Referencefinal

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 three parameters:

  1. Path to the CSV file.
  2. 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.
  3. Delimiter (optional, default ',').

The types of the columns in the CSV file are automatically inferred. The supported types are:

  • Integer: stored as a 64-bit long long int.
  • Floating point number: stored with double precision.
  • Boolean: matches the literals true and false.
  • String: stored as an std::string, matches anything that does not fall into any of the previous types.

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.

Definition at line 34 of file RCsvDS.hxx.

Public Member Functions

 RCsvDS (std::string_view fileName, bool readHeaders=true, char delimiter=',', Long64_t linesChunkSize=-1LL)
 Constructor to create a CSV RDataSource for RDataFrame. More...
 
 ~RCsvDS ()
 Destructor. More...
 
void Finalise ()
 Convenience method called after concluding an event-loop. More...
 
void FreeRecords ()
 
const std::vector< std::string > & GetColumnNames () const
 Returns a reference to the collection of the dataset's column names. More...
 
std::vector< std::pair< ULong64_t, ULong64_t > > GetEntryRanges ()
 Return ranges of entries to distribute to tasks. More...
 
std::string GetLabel ()
 Return a string representation of the datasource type. More...
 
std::string GetTypeName (std::string_view colName) const
 Type of a column as a string, e.g. More...
 
bool HasColumn (std::string_view colName) const
 Checks if the dataset has a certain column. More...
 
bool SetEntry (unsigned int slot, ULong64_t entry)
 Advance the "cursors" returned by GetColumnReaders to the selected entry for a particular slot. More...
 
void SetNSlots (unsigned int nSlots)
 Inform RDataSource of the number of processing slots (i.e. More...
 
- Public Member Functions inherited from ROOT::RDF::RDataSource
virtual ~RDataSource ()=default
 
virtual void FinaliseSlot (unsigned int)
 Convenience method called at the end of the data processing associated to a slot. More...
 
template<typename T >
std::vector< T ** > GetColumnReaders (std::string_view columnName)
 Called at most once per column by RDF. More...
 
virtual std::unique_ptr< ROOT::Detail::RDF::RColumnReaderBaseGetColumnReaders (unsigned int, std::string_view, const std::type_info &)
 If the other GetColumnReaders overload returns an empty vector, this overload will be called instead. More...
 
virtual void Initialise ()
 Convenience method called before starting an event-loop. More...
 
virtual void InitSlot (unsigned int, ULong64_t)
 Convenience method called at the start of the data processing associated to a slot. More...
 

Protected Member Functions

std::string AsString ()
 

Private Types

using ColType_t = char
 

Private Member Functions

void FillHeaders (const std::string &)
 
void FillRecord (const std::string &, Record_t &)
 
void GenerateHeaders (size_t)
 
std::vector< void * > GetColumnReadersImpl (std::string_view, const std::type_info &)
 type-erased vector of pointers to pointers to column values - one per slot More...
 
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)
 

Private Attributes

std::vector< std::deque< bool > > fBoolEvtValues
 
std::vector< std::vector< void * > > fColAddresses
 
std::map< std::string, ColType_tfColTypes
 
std::list< ColType_tfColTypesList
 
std::unique_ptr< ROOT::Internal::RRawFilefCsvFile
 
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_tfRecords
 
std::vector< std::vector< std::string > > fStringEvtValues
 

Static Private Attributes

static const std::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

- Static Public Attributes inherited from ROOT::RDF::RDataSource
static struct ROOT::RDF::RDataSource::RV2Interface V2
 
- Protected Types inherited from ROOT::RDF::RDataSource
using Record_t = std::vector< void * >
 

#include <ROOT/RCsvDS.hxx>

Inheritance diagram for ROOT::RDF::RCsvDS:
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Member Typedef Documentation

◆ ColType_t

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

Definition at line 38 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 
)

Constructor to create a CSV RDataSource for RDataFrame.

Parameters
[in]fileNamePath or URL of the CSV file.
[in]readHeaderstrue if the CSV file contains headers as first row, false otherwise (default true).
[in]delimiterDelimiter character (default ',').

Definition at line 261 of file RCsvDS.cxx.

◆ ~RCsvDS()

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

Destructor.

Definition at line 336 of file RCsvDS.cxx.

Member Function Documentation

◆ AsString()

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

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 90 of file RCsvDS.cxx.

◆ FillHeaders()

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

Definition at line 106 of file RCsvDS.cxx.

◆ FillRecord()

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

Definition at line 114 of file RCsvDS.cxx.

◆ Finalise()

void ROOT::RDF::RCsvDS::Finalise ( )
virtual

Convenience method called after concluding an event-loop.

See Initialise for more details.

Reimplemented from ROOT::RDF::RDataSource.

Definition at line 341 of file RCsvDS.cxx.

◆ FreeRecords()

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

Definition at line 305 of file RCsvDS.cxx.

◆ GenerateHeaders()

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

Definition at line 149 of file RCsvDS.cxx.

◆ GetColumnNames()

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

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

Implements ROOT::RDF::RDataSource.

Definition at line 349 of file RCsvDS.cxx.

◆ GetColumnReadersImpl()

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

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

Implements ROOT::RDF::RDataSource.

Definition at line 156 of file RCsvDS.cxx.

◆ GetEntryRanges()

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

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 354 of file RCsvDS.cxx.

◆ GetLabel()

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

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 470 of file RCsvDS.cxx.

◆ GetType()

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

Definition at line 401 of file RCsvDS.cxx.

◆ GetTypeName()

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

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

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

Parameters
[in]colNameThe name of the column

Implements ROOT::RDF::RDataSource.

Definition at line 412 of file RCsvDS.cxx.

◆ HasColumn()

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

Checks if the dataset has a certain column.

Parameters
[in]colNameThe name of the column

Implements ROOT::RDF::RDataSource.

Definition at line 417 of file RCsvDS.cxx.

◆ InferColTypes()

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

Definition at line 188 of file RCsvDS.cxx.

◆ InferType()

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

Definition at line 197 of file RCsvDS.cxx.

◆ ParseColumns()

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

Definition at line 219 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 230 of file RCsvDS.cxx.

◆ SetEntry()

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

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

Parameters
[in]slotThe data processing slot that needs to be considered
[in]entryThe 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 422 of file RCsvDS.cxx.

◆ SetNSlots()

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

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 453 of file RCsvDS.cxx.

Member Data Documentation

◆ fBoolEvtValues

std::vector<std::deque<bool> > ROOT::RDF::RCsvDS::fBoolEvtValues
private

Definition at line 62 of file RCsvDS.hxx.

◆ fColAddresses

std::vector<std::vector<void *> > ROOT::RDF::RCsvDS::fColAddresses
private

Definition at line 55 of file RCsvDS.hxx.

◆ fColTypes

std::map<std::string, ColType_t> ROOT::RDF::RCsvDS::fColTypes
private

Definition at line 53 of file RCsvDS.hxx.

◆ fColTypesList

std::list<ColType_t> ROOT::RDF::RCsvDS::fColTypesList
private

Definition at line 54 of file RCsvDS.hxx.

◆ fCsvFile

std::unique_ptr<ROOT::Internal::RRawFile> ROOT::RDF::RCsvDS::fCsvFile
private

Definition at line 47 of file RCsvDS.hxx.

◆ fDataPos

std::uint64_t ROOT::RDF::RCsvDS::fDataPos = 0
private

Definition at line 44 of file RCsvDS.hxx.

◆ fDelimiter

const char ROOT::RDF::RCsvDS::fDelimiter
private

Definition at line 48 of file RCsvDS.hxx.

◆ fDoubleEvtValues

std::vector<std::vector<double> > ROOT::RDF::RCsvDS::fDoubleEvtValues
private

Definition at line 57 of file RCsvDS.hxx.

◆ fEntryRangesRequested

ULong64_t ROOT::RDF::RCsvDS::fEntryRangesRequested = 0ULL
private

Definition at line 50 of file RCsvDS.hxx.

◆ fgColTypeMap

const std::map< RCsvDS::ColType_t, std::string > ROOT::RDF::RCsvDS::fgColTypeMap
staticprivate

Definition at line 39 of file RCsvDS.hxx.

◆ fgDoubleRegex1

const TRegexp ROOT::RDF::RCsvDS::fgDoubleRegex1
staticprivate

Definition at line 42 of file RCsvDS.hxx.

◆ fgDoubleRegex2

const TRegexp ROOT::RDF::RCsvDS::fgDoubleRegex2
staticprivate

Definition at line 42 of file RCsvDS.hxx.

◆ fgDoubleRegex3

const TRegexp ROOT::RDF::RCsvDS::fgDoubleRegex3
staticprivate

Definition at line 42 of file RCsvDS.hxx.

◆ fgFalseRegex

const TRegexp ROOT::RDF::RCsvDS::fgFalseRegex
staticprivate

Definition at line 42 of file RCsvDS.hxx.

◆ fgIntRegex

const TRegexp ROOT::RDF::RCsvDS::fgIntRegex
staticprivate

Definition at line 42 of file RCsvDS.hxx.

◆ fgTrueRegex

const TRegexp ROOT::RDF::RCsvDS::fgTrueRegex
staticprivate

Definition at line 42 of file RCsvDS.hxx.

◆ fHeaders

std::vector<std::string> ROOT::RDF::RCsvDS::fHeaders
private

Definition at line 52 of file RCsvDS.hxx.

◆ fLinesChunkSize

const Long64_t ROOT::RDF::RCsvDS::fLinesChunkSize
private

Definition at line 49 of file RCsvDS.hxx.

◆ fLong64EvtValues

std::vector<std::vector<Long64_t> > ROOT::RDF::RCsvDS::fLong64EvtValues
private

Definition at line 58 of file RCsvDS.hxx.

◆ fNSlots

unsigned int ROOT::RDF::RCsvDS::fNSlots = 0U
private

Definition at line 46 of file RCsvDS.hxx.

◆ fProcessedLines

ULong64_t ROOT::RDF::RCsvDS::fProcessedLines = 0ULL
private

Definition at line 51 of file RCsvDS.hxx.

◆ fReadHeaders

bool ROOT::RDF::RCsvDS::fReadHeaders = false
private

Definition at line 45 of file RCsvDS.hxx.

◆ fRecords

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

Definition at line 56 of file RCsvDS.hxx.

◆ fStringEvtValues

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

Definition at line 59 of file RCsvDS.hxx.

Libraries for ROOT::RDF::RCsvDS:
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The documentation for this class was generated from the following files:
Rcpp::as
TString as(SEXP s)
Definition: RExports.h:71