-- | -- Module : Database.LevelDB.Types -- Copyright : (c) 2012-2013 The leveldb-haskell Authors -- License : BSD3 -- Maintainer : kim.altintop@gmail.com -- Stability : experimental -- Portability : non-portable -- module Database.LevelDB.Types ( BatchOp (..) , BloomFilter (..) , Comparator (..) , Compression (..) , FilterPolicy (..) , Options (..) , Property (..) , ReadOptions (..) , Snapshot (..) , WriteBatch , WriteOptions (..) , defaultOptions , defaultReadOptions , defaultWriteOptions ) where import Data.ByteString (ByteString) import Data.Default import Foreign import Database.LevelDB.C -- | Snapshot handle newtype Snapshot = Snapshot SnapshotPtr deriving (Eq) -- | Compression setting data Compression = NoCompression | Snappy deriving (Eq, Show) -- | User-defined comparator newtype Comparator = Comparator (ByteString -> ByteString -> Ordering) -- | User-defined filter policy data FilterPolicy = FilterPolicy { fpName :: String , createFilter :: [ByteString] -> ByteString , keyMayMatch :: ByteString -> ByteString -> Bool } -- | Represents the built-in Bloom Filter newtype BloomFilter = BloomFilter FilterPolicyPtr -- | Options when opening a database data Options = Options { blockRestartInterval :: !Int -- ^ Number of keys between restart points for delta encoding of keys. -- -- This parameter can be changed dynamically. Most clients should leave -- this parameter alone. -- -- Default: 16 , blockSize :: !Int -- ^ Approximate size of user data packed per block. -- -- Note that the block size specified here corresponds to uncompressed -- data. The actual size of the unit read from disk may be smaller if -- compression is enabled. -- -- This parameter can be changed dynamically. -- -- Default: 4k , cacheSize :: !Int -- ^ Control over blocks (user data is stored in a set of blocks, and a -- block is the unit of reading from disk). -- -- If > 0, use the specified cache (in bytes) for blocks. If 0, leveldb -- will automatically create and use an 8MB internal cache. -- -- Default: 0 , comparator :: !(Maybe Comparator) -- ^ Comparator used to defined the order of keys in the table. -- -- If 'Nothing', the default comparator is used, which uses lexicographic -- bytes-wise ordering. -- -- NOTE: the client must ensure that the comparator supplied here has the -- same name and orders keys /exactly/ the same as the comparator provided -- to previous open calls on the same DB. -- -- Default: Nothing , compression :: !Compression -- ^ Compress blocks using the specified compression algorithm. -- -- This parameter can be changed dynamically. -- -- Default: 'Snappy' , createIfMissing :: !Bool -- ^ If true, the database will be created if it is missing. -- -- Default: False , errorIfExists :: !Bool -- ^ It true, an error is raised if the database already exists. -- -- Default: False , maxOpenFiles :: !Int -- ^ Number of open files that can be used by the DB. -- -- You may need to increase this if your database has a large working set -- (budget one open file per 2MB of working set). -- -- Default: 1000 , paranoidChecks :: !Bool -- ^ If true, the implementation will do aggressive checking of the data -- it is processing and will stop early if it detects any errors. -- -- This may have unforeseen ramifications: for example, a corruption of -- one DB entry may cause a large number of entries to become unreadable -- or for the entire DB to become unopenable. -- -- Default: False , writeBufferSize :: !Int -- ^ Amount of data to build up in memory (backed by an unsorted log on -- disk) before converting to a sorted on-disk file. -- -- Larger values increase performance, especially during bulk loads. Up to -- to write buffers may be held in memory at the same time, so you may -- with to adjust this parameter to control memory usage. Also, a larger -- write buffer will result in a longer recovery time the next time the -- database is opened. -- -- Default: 4MB , filterPolicy :: !(Maybe (Either BloomFilter FilterPolicy)) } defaultOptions :: Options defaultOptions = Options { blockRestartInterval = 16 , blockSize = 4096 , cacheSize = 0 , comparator = Nothing , compression = Snappy , createIfMissing = False , errorIfExists = False , maxOpenFiles = 1000 , paranoidChecks = False , writeBufferSize = 4 `shift` 20 , filterPolicy = Nothing } instance Default Options where def = defaultOptions -- | Options for write operations data WriteOptions = WriteOptions { sync :: !Bool -- ^ If true, the write will be flushed from the operating system buffer -- cache (by calling WritableFile::Sync()) before the write is considered -- complete. If this flag is true, writes will be slower. -- -- If this flag is false, and the machine crashes, some recent writes may -- be lost. Note that if it is just the process that crashes (i.e., the -- machine does not reboot), no writes will be lost even if sync==false. -- -- In other words, a DB write with sync==false has similar crash semantics -- as the "write()" system call. A DB write with sync==true has similar -- crash semantics to a "write()" system call followed by "fsync()". -- -- Default: False } deriving (Eq, Show) defaultWriteOptions :: WriteOptions defaultWriteOptions = WriteOptions { sync = False } instance Default WriteOptions where def = defaultWriteOptions -- | Options for read operations data ReadOptions = ReadOptions { verifyCheckSums :: !Bool -- ^ If true, all data read from underlying storage will be verified -- against corresponding checksums. -- -- Default: False , fillCache :: !Bool -- ^ Should the data read for this iteration be cached in memory? Callers -- may with to set this field to false for bulk scans. -- -- Default: True , useSnapshot :: !(Maybe Snapshot) -- ^ If 'Just', read as of the supplied snapshot (which must belong to the -- DB that is being read and which must not have been released). If -- 'Nothing', use an implicit snapshot of the state at the beginning of -- this read operation. -- -- Default: Nothing } deriving (Eq) defaultReadOptions :: ReadOptions defaultReadOptions = ReadOptions { verifyCheckSums = False , fillCache = True , useSnapshot = Nothing } instance Default ReadOptions where def = defaultReadOptions type WriteBatch = [BatchOp] -- | Batch operation data BatchOp = Put ByteString ByteString | Del ByteString deriving (Eq, Show) -- | Properties exposed by LevelDB data Property = NumFilesAtLevel Int | Stats | SSTables deriving (Eq, Show)