Portability	non-portable
Stability	experimental
Maintainer	kim.altintop@gmail.com
Safe Haskell	Safe-Infered

Database.LevelDB

Contents

Exported Types
Basic Database Manipulation
Administrative Functions
Iteration

Description

LevelDB Haskell binding.

The API closely follows the C-API of LevelDB. For more information, see: http://leveldb.googlecode.com

Basic example:

 withLevelDB "/tmp/leveldbtest" [CreateIfMissing, CacheSize 1024] $ \db -> do
     put db [] "foo" "bar"
     get db [] "foo" >>= print
     delete db [] "foo"
     get db [] "foo" >>= print

Batch write and iterating:

 withLevelDB "/tmp/leveldbtest" [CreateIfMissing, CacheSize 1024] $ \db -> do
     write db [Sync] [ Put "a" "one"
                     , Put "b" "two"
                     , Put "c" "three" ]
     dumpEntries db []

     where
         dumpEntries db opts =
             withIterator db opts $ \iter -> do
                 iterFirst iter
                 iterItems iter >>= print

Synopsis

Exported Types

data DB Source

Database handle

Instances

Eq DB

data BatchOp Source

Batch operation

Constructors

Put ByteString ByteString
Del ByteString

Instances

Eq BatchOp
Show BatchOp

data Compression Source

Compression setting

Constructors

NoCompression
Snappy

Instances

Eq Compression
Show Compression

data Option Source

Options when opening a database

Constructors

CreateIfMissing
ErrorIfExists
ParanoidChecks
WriteBufferSize Int
MaxOpenFiles Int
BlockSize Int
BlockRestartInterval Int
UseCompression Compression
CacheSize Int

Instances

Eq Option
Show Option

type Options = [Option]Source

data ReadOption Source

Options for read operations

Constructors

VerifyCheckSums
FillCache
UseSnapshot Snapshot

Instances

Eq ReadOption

type ReadOptions = [ReadOption]Source

data Snapshot Source

Snapshot handle

Instances

Eq Snapshot

type WriteBatch = [BatchOp]Source

data WriteOption Source

Options for write operations

Constructors

Sync	fsync the rows written immediately

Instances

Eq WriteOption
Show WriteOption

type WriteOptions = [WriteOption]Source

type Range = (ByteString, ByteString)Source

Basic Database Manipulation

withLevelDB :: FilePath -> Options -> (DB -> IO a) -> IO aSource

Run an action on a database

withSnapshot :: DB -> (Snapshot -> IO a) -> IO aSource

Run an action with a snapshot of the database.

put :: DB -> WriteOptions -> ByteString -> ByteString -> IO ()Source

Write a key/value pair

delete :: DB -> WriteOptions -> ByteString -> IO ()Source

Delete a key/value pair

write :: DB -> WriteOptions -> WriteBatch -> IO ()Source

Perform a batch mutation

get :: DB -> ReadOptions -> ByteString -> IO (Maybe ByteString)Source

Read a value by key

Administrative Functions

data Property Source

Properties exposed by LevelDB

Constructors

NumFilesAtLevel Int
Stats
SSTables

Instances

Eq Property
Show Property

getProperty :: DB -> Property -> IO (Maybe ByteString)Source

Get a DB property

destroy :: FilePath -> Options -> IO ()Source

Destroy the given leveldb database.

repair :: FilePath -> Options -> IO ()Source

Repair the given leveldb database.

approximateSize :: DB -> Range -> IO Int64 Source

Inspect the approximate sizes of the different levels

Iteration

data Iterator Source

Iterator handle

Instances

Eq Iterator

withIterator :: DB -> ReadOptions -> (Iterator -> IO a) -> IO aSource

Run an action with an Iterator. The iterator will be closed after the action returns or an error is thrown. Thus, the iterator will not be valid after this function terminates.

iterOpen :: DB -> ReadOptions -> IO Iterator Source

Create an Iterator. Consider using withIterator.

iterClose :: Iterator -> IO ()Source

Release an Iterator. Consider using withIterator.

iterValid :: Iterator -> IO Bool Source

An iterator is either positioned at a key/value pair, or not valid. This function returns true iff the iterator is valid.

iterSeek :: Iterator -> ByteString -> IO ()Source

Position at the first key in the source that is at or past target. The iterator is valid after this call iff the source contains an entry that comes at or past target.

iterFirst :: Iterator -> IO ()Source

Position at the first key in the source. The iterator is valid after this call iff the source is not empty.

iterLast :: Iterator -> IO ()Source

Position at the last key in the source. The iterator is valid after this call iff the source is not empty.

iterNext :: Iterator -> IO ()Source

Moves to the next entry in the source. After this call, iterValid is true iff the iterator was not positioned the last entry in the source.

iterPrev :: Iterator -> IO ()Source

Moves to the previous entry in the source. After this call, iterValid is true iff the iterator was not positioned at the first entry in the source.

iterKey :: Iterator -> IO ByteString Source

Return the key for the current entry. The underlying storage for the returned slice is valid only until the next modification of the iterator.

iterValue :: Iterator -> IO ByteString Source

Return the value for the current entry. The underlying storage for the returned slice is valid only until the next modification of the iterator.

mapIter :: (Iterator -> IO a) -> Iterator -> IO [a]Source

Map a function over an iterator, returning the value. The iterator should be put in the right position prior to calling this with the iterator.

iterItems :: Iterator -> IO [(ByteString, ByteString)]Source

Return a list of key and value tuples from an iterator. The iterator should be put in the right position prior to calling this with the iterator.

iterKeys :: Iterator -> IO [ByteString]Source

Return a list of key from an iterator. The iterator should be put in the right position prior to calling this with the iterator.

iterValues :: Iterator -> IO [ByteString]Source

Return a list of values from an iterator. The iterator should be put in the right position prior to calling this with the iterator.