{-# LANGUAGE OverloadedStrings #-}
-- |
-- Comprehensive walkthough of the functionality provided by this library.
--
module Main where
import Control.Monad
import Control.Monad.IO.Class (liftIO)
import Control.Monad.Trans.Resource (release)
import Data.ByteString.Char8 hiding (take)
import Data.Default
import Database.LevelDB
import qualified Database.LevelDB.Streaming as S
import Prelude hiding (putStrLn)
main :: IO ()
main = runResourceT $ do
printVersion
db <- open "/tmp/leveltest"
defaultOptions{ createIfMissing = True
, cacheSize= 2048
}
put db def "foo" "bar"
get db def "foo" >>= liftIO . print
delete db def "foo"
get db def "foo" >>= liftIO . print
(releaseSnap, snap) <- createSnapshot' db
write db def{sync = True} [ Put "a" "one"
, Put "b" "two"
, Put "c" "three"
]
withIterator db def{useSnapshot = Just snap} $ \iter -> dumpEntries iter
-- early release snapshot
release releaseSnap
-- here, we keep the iterator around for later reuse.
-- Note that we don't explicitly release it (and thus don't keep the release
-- key). The iterator will be released when runResourceT terminates.
iter <- iterOpen db def
dumpEntries iter
approximateSize db ("a", "z") >>= liftIO . print
getProperty db SSTables >>= printProperty "sstables"
getProperty db Stats >>= printProperty "stats"
getProperty db (NumFilesAtLevel 1) >>= printProperty "num files at level"
write db def [ Del "a"
, Del "b"
, Del "c"
]
dumpEntries iter
return ()
where
dumpEntries iter = liftIO $
S.toList (S.entrySlice iter S.AllKeys S.Asc)
>>= print
printProperty l p = liftIO $ do
putStrLn l
maybe (putStrLn "n/a") putStrLn p
printVersion = do
v <- versionBS
liftIO . putStrLn $ "LevelDB Version: " `append` v
versionBS = do
(major, minor) <- version
return $ intToBs major `append` "." `append` intToBs minor
intToBs :: Int -> ByteString
intToBs = pack . show