[Haskell-beginners] [Code Review] csv file to sqlite3

28 Jul 2011

      Hi,

I am trying to write a simple Haskell program to read from a .csv file
and write to a .sqlite3 database. Can anyone please review the
following code?

=== BEGIN ===

import Text.ParserCombinators.Parsec

import Database.HDBC
import Database.HDBC.Sqlite3
import Control.Monad(when)

-- | Initialize DB and return database Connection
connect :: FilePath -> IO Connection
connect fp =
    do dbh <- connectSqlite3 fp
       prepDB dbh
       return dbh

prepDB :: IConnection conn => conn -> IO ()
prepDB dbh =
       do tables <- getTables dbh
          when (not ("entries" `elem` tables)) $
               do run dbh "CREATE TABLE entries ( \
                  \id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, \
                  \first TEXT, \
		  \second TEXT, \
		  \third TEXT)" []
                  return ()
          commit dbh

csvFile = endBy line eol
line = sepBy cell (char ';')
cell = quotedCell <|> many (noneOf ";\n\r")

quotedCell =
    do char '"'
       content <- many quotedChar
       char '"' <?> "quote at end of cell"
       return content

quotedChar =
           noneOf "\""
    <|> try (string "\"\"" >> return '"')

eol =   try (string "\n\r")
    <|> try (string "\r\n")
    <|> string "\n"
    <|> string "\r"
    <?> "end of line"

process :: [String] -> IO ()
process r = do
        conn <- connectSqlite3 "simple1.db"
        run conn "INSERT INTO entries (first, second, third) VALUES
(?, ?, ?)" (map toSql r)
        commit conn
        disconnect conn

main = do
     dbh <- connect "simple1.db"
     do c <- getContents
        case parse csvFile "(stdin)" c of
             Left e -> do putStrLn "Error parsing input:"
                          print e
             Right r -> do
                   mapM_ process r

=== END ===

Appreciate any suggestions, improvements in this regard.

Thanks!

SK

-- 
Shakthi Kannan
http://www.shakthimaan.com