Copyright	(c) Nikos Karagiannidis 2018
License	BSD3
Maintainer	nkarag@gmail.com
Stability	stable
Portability	POSIX
Safe Haskell	None
Language	Haskell2010

RTable.Data.CSV

Contents

The CSV data type
Read/Write CSV
CSV as Tabular data
CSV I/O
Basic CSV processing
Misc
Exceptions

Description

This module implements the RTabular instance of the CSV data type, i.e., implements the interface by which a CSV file can be transformed to/from an RTable. It is required when we want to do ETL/ELT over CSV files with the DBFunctor package (i.e., with the Julius EDSL for ETL/ELT found in the Etl.Julius module).

The minimum requirement for implementing an RTabular instance for a data type is to implement the toRTable and fromRTable functions. Apart from these two functions, this module also exports functions for reading and writing CSV data from/to CSV files. Also it supports all types of delimiters (not only commas) and CSVs with or without headers. (see CSVOptions)

For the CSV data type this module uses the Cassava library (Data.Csv)

Synopsis

newtype CSV = CSV {
- csv :: Vector Row
}
type Row = Vector Column
type Column = Field
data CSVOptions = CSVOptions {
- delimiter :: Char
- hasHeader :: YesNo
}
data YesNo
- = Yes
- | No
readCSV :: FilePath -> IO CSV
readCSVwithOptions :: CSVOptions -> FilePath -> IO CSV
readCSVFile :: FilePath -> IO ByteString
writeCSV :: FilePath -> CSV -> IO ()
writeCSVFile :: FilePath -> ByteString -> IO ()
toRTable :: RTabular a => RTableMData -> a -> RTable
fromRTable :: RTabular a => RTableMData -> RTable -> a
printCSV :: CSV -> IO ()
printCSVFile :: ByteString -> IO ()
copyCSV :: FilePath -> FilePath -> IO ()
selectNrows :: Int -> CSV -> CSV
projectByIndex :: [Int] -> CSV -> CSV
headCSV :: CSV -> Row
tailCSV :: CSV -> CSV
csvHeaderFromRtable :: RTable -> Header
data CsvFileDecodingError = CsvFileDecodingError FilePath Text
data CSVColumnToRDataTypeError = CSVColumnToRDataTypeError ColumnName Text

The CSV data type

newtype CSV Source #

Definition of a CSV file. Treating CSV data as opaque byte strings

Constructors

CSV
Fields csv :: Vector Row

Instances

RTabular CSV Source #	CSV data are "Tabular" data thus implement the `RTabular` interface
Instance details Defined in RTable.Data.CSV Methods toRTable :: RTableMData -> CSV -> RTable Source # fromRTable :: RTableMData -> RTable -> CSV Source #

type Row = Vector Column Source #

Definition of a CSV Row. Essentially a Row is just a Vector of ByteString

type Column = Field Source #

Definition of a CSV column.

data CSVOptions Source #

Options for a CSV file (e.g., delimiter specification, header specification etc.)

Constructors

CSVOptions
Fields delimiter :: Char hasHeader :: YesNo

data YesNo Source #

Yes or No sum type

Constructors

Yes
No

Read/Write CSV

readCSV Source #

Arguments

:: FilePath	the CSV file
-> IO CSV	the output CSV type

reads a CSV file and returns a CSV data type (Treating CSV data as opaque byte strings)

readCSVwithOptions Source #

Arguments

:: CSVOptions
-> FilePath	the CSV file
-> IO CSV	the output CSV type

reads a CSV file based on input options (delimiter and header option) and returns a CSV data type (Treating CSV data as opaque byte strings)

readCSVFile Source #

Arguments

:: FilePath	the CSV file
-> IO ByteString	the output CSV

reads a CSV file and returns a lazy bytestring

writeCSV Source #

Arguments

:: FilePath	the csv file to be created
-> CSV	input `CSV`
-> IO ()

write a CSV to a newly created csv file

writeCSVFile Source #

Arguments

:: FilePath	the csv file to be created
-> ByteString	input CSV
-> IO ()

write a CSV (bytestring) to a newly created csv file

CSV as Tabular data

toRTable :: RTabular a => RTableMData -> a -> RTable Source #

fromRTable :: RTabular a => RTableMData -> RTable -> a Source #

CSV I/O

printCSV Source #

Arguments

:: CSV	input `CSV` to be printed on screen
-> IO ()

print input CSV on screen

printCSVFile Source #

Arguments

:: ByteString	input CSV to be printed on screen
-> IO ()

print input CSV on screen

Basic CSV processing

copyCSV Source #

Arguments

:: FilePath	input csv file
-> FilePath	output csv file
-> IO ()

copy input csv file to specified output csv file

selectNrows Source #

Arguments

:: Int	Number of rows to select
-> CSV	Input csv
-> CSV	Output csv

selectNrows: Returns the first N rows from a CSV file

projectByIndex Source #

Arguments

:: [Int]	input list of column indexes
-> CSV	input csv
-> CSV	output CSV

Column projection on an input CSV file where desired columns are defined by position (index) in the CSV.

headCSV :: CSV -> Row Source #

O(1) First row

tailCSV :: CSV -> CSV Source #

O(1) Yield all but the first row without copying. The CSV may not be empty.

Misc

csvHeaderFromRtable :: RTable -> Header Source #

creates a Header (as defined in Data.Csv) from an RTable

Exceptions

data CsvFileDecodingError Source #

Exception to signify an error in decoding a CSV file into a CSV data type

Constructors

CsvFileDecodingError FilePath Text

Instances

Eq CsvFileDecodingError Source #
Instance details Defined in RTable.Data.CSV Methods (==) :: CsvFileDecodingError -> CsvFileDecodingError -> Bool # (/=) :: CsvFileDecodingError -> CsvFileDecodingError -> Bool #
Show CsvFileDecodingError Source #
Instance details Defined in RTable.Data.CSV Methods showsPrec :: Int -> CsvFileDecodingError -> ShowS # show :: CsvFileDecodingError -> String # showList :: [CsvFileDecodingError] -> ShowS #
Exception CsvFileDecodingError Source #
Instance details Defined in RTable.Data.CSV Methods toException :: CsvFileDecodingError -> SomeException # fromException :: SomeException -> Maybe CsvFileDecodingError # displayException :: CsvFileDecodingError -> String #

data CSVColumnToRDataTypeError Source #

This exception signifies an error in parsing a CSV Column to an RDataType value

Constructors

CSVColumnToRDataTypeError ColumnName Text

Instances

Eq CSVColumnToRDataTypeError Source #
Instance details Defined in RTable.Data.CSV Methods (==) :: CSVColumnToRDataTypeError -> CSVColumnToRDataTypeError -> Bool # (/=) :: CSVColumnToRDataTypeError -> CSVColumnToRDataTypeError -> Bool #
Show CSVColumnToRDataTypeError Source #
Instance details Defined in RTable.Data.CSV Methods showsPrec :: Int -> CSVColumnToRDataTypeError -> ShowS # show :: CSVColumnToRDataTypeError -> String # showList :: [CSVColumnToRDataTypeError] -> ShowS #
Exception CSVColumnToRDataTypeError Source #
Instance details Defined in RTable.Data.CSV Methods toException :: CSVColumnToRDataTypeError -> SomeException # fromException :: SomeException -> Maybe CSVColumnToRDataTypeError # displayException :: CSVColumnToRDataTypeError -> String #