cql-3.0.7: Cassandra CQL binary protocol.

Safe HaskellNone
LanguageHaskell2010

Database.CQL.Protocol

Contents

Description

The CQL native protocol is a binary frame-based protocol where each frame has a Header, a Length and a body. The protocol distinguishes Requests and Responses.

Some usage examples:

Constructing and Serialising a Request

let q = QueryString "select peer from system.peers where data_center = ? and rack = ?"
    p = QueryParams One False ("uk-1", "r-0") Nothing Nothing Nothing
    r = RqQuery (Query q p :: Query R (Text, Text) (Identity IP))
    i = mkStreamId 0
in pack V3 noCompression False i r

Deserialising a Response

-- assuming bh contains the raw header byte string and bb the raw
-- body byte string.
case header V3 bh of
    Left  e -> ...
    Right h -> unpack noCompression h bb

A generic query processing function

query :: (Tuple a, Tuple b) => Version -> Socket -> QueryString k a b -> QueryParams a -> IO (Response k a b)
query v s q p = do
    let i = mkStreamId 0
    sendToServer s (pack v noCompression False i (RqQuery (Query q p)))
    b <- recv (if v == V3 then 9 else 8) s
    h <- either (throwIO . MyException) return (header v b)
    when (headerType h == RqHeader) $
        throwIO UnexpectedRequestHeader
    let len = lengthRepr (bodyLength h)
    x <- recv (fromIntegral len) s
    case unpack noCompression h x of
        Left e              -> throwIO $ AnotherException e
        Right (RsError _ e) -> throwIO e
        Right response      -> return response

Synopsis

Cql type-class

class Cql a where Source

A type that can be converted from and to some CQL Value.

This type-class is used to map custom types to Cassandra data-types. For example:

newtype MyType = MyType Int32

instance Cql MyType where
    ctype              = Tagged IntColumn
    toCql (MyType i)   = CqlInt i
    fromCql (CqlInt i) = Right (MyType i)
    fromCql _          = Left "Expected CqlInt"

Methods

ctype :: Tagged a ColumnType Source

the column-type of a

toCql :: a -> Value Source

map a to some CQL data-type

fromCql :: Value -> Either String a Source

map a CQL value back to a

Instances

Cql Bool Source 
Cql Double Source 
Cql Float Source 
Cql Int32 Source 
Cql Int64 Source 
Cql Integer Source 
Cql Decimal Source 
Cql IP Source 
Cql Text Source 
Cql UTCTime Source 
Cql UUID Source 
Cql TimeUuid Source 
Cql Counter Source 
Cql Blob Source 
Cql Ascii Source 
Cql a => Cql [a] Source 
Cql a => Cql (Maybe a) Source

Please note that due to the fact that Cassandra internally represents empty collection type values (i.e. lists, maps and sets) as null, we can not distinguish Just [] from Nothing on response decoding.

Cql a => Cql (Set a) Source 
(Cql a, Cql b) => Cql (Map a b) Source 

Basic type definitions

newtype Keyspace Source

Constructors

Keyspace 

Fields

unKeyspace :: Text
 

newtype Table Source

Constructors

Table 

Fields

unTable :: Text
 

newtype PagingState Source

Opaque token passed to the server to continue result paging.

Constructors

PagingState 

newtype QueryId k a b Source

ID representing a prepared query.

Constructors

QueryId 

Instances

Eq (QueryId k a b) Source 
Show (QueryId k a b) Source 

newtype QueryString k a b Source

Constructors

QueryString 

Fields

unQueryString :: Text
 

Instances

data Version Source

CQL binary protocol version.

Constructors

V2

version 2

V3

version 3

data CqlVersion Source

The CQL version (not the binary protocol version).

Constructors

Cqlv300 
CqlVersion !Text 

newtype Blob Source

Constructors

Blob 

Fields

fromBlob :: ByteString
 

newtype Set a Source

Constructors

Set 

Fields

fromSet :: [a]
 

Instances

Show a => Show (Set a) Source 
Cql a => Cql (Set a) Source 

newtype Map a b Source

Constructors

Map 

Fields

fromMap :: [(a, b)]
 

Instances

(Show a, Show b) => Show (Map a b) Source 
(Cql a, Cql b) => Cql (Map a b) Source 

data Value Source

A CQL value. The various constructors correspond to CQL data-types for individual columns in Cassandra.

newtype Tagged a b Source

Tag some value with a phantom type.

Constructors

Tagged 

Fields

untag :: b
 

retag :: Tagged a c -> Tagged b c Source

data R Source

data W Source

data S Source

Header

data Header Source

Protocol frame header.

Instances

data HeaderType Source

Constructors

RqHeader

A request frame header.

RsHeader

A response frame header.

header :: Version -> ByteString -> Either String Header Source

Deserialise a frame header using the version specific decoding format.

Length

newtype Length Source

The type denoting a protocol frame length.

Constructors

Length 

Fields

lengthRepr :: Int32
 

StreamId

data StreamId Source

Streams allow multiplexing of requests over a single communication channel. The StreamId correlates Requests with Responses.

mkStreamId :: Integral i => i -> StreamId Source

Create a StreamId from the given integral value. In version 2, a StreamId is an Int8 and in version 3 an Int16.

fromStreamId :: StreamId -> Int Source

Convert the stream ID to an integer.

Flags

data Flags Source

Type representing header flags. Flags form a monoid and can be used as in compress <> tracing <> mempty.

compress :: Flags Source

Compression flag. If set, the frame body is compressed.

tracing :: Flags Source

Tracing flag. If a request support tracing and the tracing flag was set, the response to this request will have the tracing flag set and contain tracing information.

isSet :: Flags -> Flags -> Bool Source

Check if a particular flag is present.

Request

data Request k a b Source

The type corresponding to the protocol request frame.

The type parameter k denotes the kind of request. It is present to allow distinguishing read operations from write operations. Use R for read, W for write and S for schema related operations.

a represents the argument type and b the return type of this request.

Instances

Show a => Show (Request k a b) Source 

getOpCode :: Request k a b -> OpCode Source

Get the protocol OpCode corresponding to the given Request.

pack Source

Arguments

:: Tuple a 
=> Version

protocol version, which determines the encoding

-> Compression

compression to use

-> Bool

enable/disable tracing

-> StreamId

the stream Id to use

-> Request k a b

the actual request to serialise

-> Either String ByteString 

Serialise the given request, optionally using compression. The result is either an error description in case of failure or a binary protocol frame, including Header, Length and body.

Options

data Options Source

An options request, send prior to Startup to request the server's startup options.

Constructors

Options 

Instances

Startup

data Startup Source

A startup request which is used when initialising a connection to the server. It specifies the CQL version to use and optionally the compression algorithm.

Instances

Auth Response

newtype AuthResponse Source

A request send in response to a previous authentication challenge.

Constructors

AuthResponse ByteString 

Register

newtype Register Source

Register's the connection this request is made through, to receive server events.

Constructors

Register [EventType] 

Instances

data EventType Source

Event types to register.

Constructors

TopologyChangeEvent

events related to change in the cluster topology

StatusChangeEvent

events related to change of node status

SchemaChangeEvent

events related to schema change

Instances

Query

data Query k a b Source

A CQL query (select, insert, etc.).

Constructors

Query !(QueryString k a b) !(QueryParams a) 

Instances

Show a => Show (Query k a b) Source 

data QueryParams a Source

Query parameters.

Constructors

QueryParams 

Fields

consistency :: !Consistency

consistency leven to use

skipMetaData :: !Bool

skip metadata in response

values :: a

query arguments

pageSize :: Maybe Int32

desired result set size

queryPagingState :: Maybe PagingState
 
serialConsistency :: Maybe SerialConsistency
 

Instances

data SerialConsistency Source

Consistency level for the serial phase of conditional updates.

Batch

data Batch Source

Allows executing a list of queries (prepared or not) as a batch.

Instances

data BatchQuery where Source

A GADT to unify queries and prepared queries both of which can be used in batch requests.

Constructors

BatchQuery :: (Show a, Tuple a, Tuple b) => !(QueryString W a b) -> !a -> BatchQuery 
BatchPrepared :: (Show a, Tuple a, Tuple b) => !(QueryId W a b) -> !a -> BatchQuery 

data BatchType Source

Constructors

BatchLogged

default, uses a batch log for atomic application

BatchUnLogged

skip the batch log

BatchCounter

used for batched counter updates

Instances

Prepare

newtype Prepare k a b Source

Prepare a query for later execution (cf. Execute).

Constructors

Prepare (QueryString k a b) 

Instances

Show (Prepare k a b) Source 

Execute

data Execute k a b Source

Executes a prepared query.

Constructors

Execute !(QueryId k a b) !(QueryParams a) 

Instances

Show a => Show (Execute k a b) Source 

Response

data Response k a b Source

The type corresponding to the protocol response frame.

The type parameter k denotes the kind of response. It is present to allow distinguishing read operations from write operations. Use R for read, W for write and S for schema related operations.

a represents the argument type and b the return type of this response.

Instances

Show b => Show (Response k a b) Source 

unpack :: (Tuple a, Tuple b) => Compression -> Header -> ByteString -> Either String (Response k a b) Source

Deserialise a Response from the given ByteString.

Ready

data Ready Source

The server is ready to process queries. Response of a Startup request.

Constructors

Ready 

Instances

Authenticate

newtype Authenticate Source

The server requires authentication.

Constructors

Authenticate Text 

newtype AuthChallenge Source

A server-send authentication challenge.

newtype AuthSuccess Source

Indicates the success of an authentication phase.

Constructors

AuthSuccess (Maybe ByteString) 

Result

data MetaData Source

Part of a RowsResult. Describes the result set.

Instances

data ColumnSpec Source

The column specification. Part of MetaData unless skipMetaData in QueryParams was True.

Constructors

ColumnSpec 

Supported

data Supported Source

The startup options supported by the server. Response of an Options request.

Instances

Event

data Event Source

Messages send by the server without request, if the connection has been Registered to receive such events.

Instances

Error

Row, Tuple and Record

class PrivateTuple a => Tuple a Source

Instances

count :: PrivateTuple a => Tagged a Int Source

check :: PrivateTuple a => Tagged a ([ColumnType] -> [ColumnType]) Source

tuple :: PrivateTuple a => Version -> [ColumnType] -> Get a Source

store :: PrivateTuple a => Version -> Putter a Source

data Row Source

A row is a vector of Values.

fromRow :: Cql a => Int -> Row -> Either String a Source

Convert a row element.

class Record a where Source

Record/Tuple conversion. For example:

data Peer = Peer
    { peerAddr :: IP
    , peerRPC  :: IP
    , peerDC   :: Text
    , peerRack :: Text
    } deriving Show

recordInstance ''Peer

map asRecord <$> performQuery "SELECT peer, rpc_address, data_center, rack FROM system.peers"

The generated type-class instance maps between record and tuple constructors:

type instance TupleType Peer = (IP, IP, Text, Text)

instance Record Peer where
    asTuple (Peer a b c d) = (a, b, c, d)
    asRecord (a, b, c, d)  = Peer a b c d

Methods

asTuple :: a -> TupleType a Source

asRecord :: TupleType a -> a Source

type family TupleType a Source