hascas

Cassandra CQL driver for haskell

This is a work in progress driver for cassandra.

GHC 7.10.3 and 8.0.x are supported.

It currently has:

• Select
• Insert
• Update
• Delete
• Prepared Queries
• Batch Queries
• Automatic Records Conversion
• Collections
• Automatic reconnection on connection errors

The driver gets the list of all nodes in the cluster and load balances amongst them.

Example

Look at the project in the example directory.

How it looks :

data Emp = Emp {
  empID    :: Int64,
  deptID   :: Int32,
  alive    :: Bool ,
  id       :: UUID,
  name     :: CQLString,
  salary   :: CQLDouble,
  someList :: CQLList Int32,
  someSet  :: CQLSet CQLDouble,
  someMap  :: CQLMap CQLString CQLString
}
  deriving(Show, Eq)

deriveBuildRec ''Emp

main :: IO ()
main = do
    candle <- CQL.init "127.0.0.1" (PortNumber 9042) (RetryInterval 1000000)

    res <- flip runReaderT candle $ runExceptT $ do
      let q = create "keyspace demodb WITH REPLICATION = {'class' : 'SimpleStrategy','replication_factor': 1}"
      runCQL LOCAL_ONE q

      --create a table
      let tableQuery = "TABLE demodb.emp (empID bigint,deptID int,alive boolean,id uuid,name varchar,salary double,"
                       ++ "someset set<double>,somelist list<int>,somemap map<text, text>,PRIMARY KEY (empID, deptID))"

      let q = create tableQuery
      runCQL LOCAL_ONE q

      --execute prepared queries
      p <- prepare "INSERT INTO demodb.emp (empID,deptID,alive,id,name,salary,somelist,someset,somemap) VALUES (?,?,?,?,?,?,?,?,?)"
      execCQL LOCAL_ONE p [
            put (104::Int64),
            put (15::Int32),
            put True,
            put $ fromJust $ fromString "38d0ceb1-9e3e-427c-bc36-0106398f672b",
            put $ CQLString "Hot Shot",
            put $ CQLDouble 100000.0,
            put ((CQLList [1,2,3,4,5,6]) :: CQLList Int32),
            put ((CQLSet $ fromList [CQLDouble 0.001, CQLDouble 1000.0]) :: CQLSet CQLDouble),
            put $ CQLMap $ DMS.fromList [(CQLString "some", CQLString "Things")]]

      -- execute prepared queries and get results
      p <- prepare "select empID, deptID, alive, id, name, salary, someset, somemap, somelist from demodb.emp where empid = ? and deptid = ?"
      res <- execCQL LOCAL_ONE p [
            put (104::Int64),
            put (15::Int32)]
      liftIO $ print $ catMaybes ((fmap fromRow res)::[Maybe Emp])
      liftIO $ print (fromCQL (Prelude.head res) (CQLString "salary")::Maybe Double)
      liftIO $ print (fromCQL (Prelude.head res) (CQLString "name")::Maybe CQLString)

      --select rows from table
      let q = select "demodb.emp" # where' "empID" (104::Int64) # and' "deptID" (15::Int32)
      rows <- runCQL LOCAL_ONE q
      liftIO $ print $ catMaybes ((fmap fromRow res)::[Maybe Emp])

      --batch queries
      p <- prepare "INSERT INTO demodb.emp (empID, deptID, alive, id, name, salary) VALUES (?, ?, ?, ?, ?, ?)"
      let q = batch (update "demodb.emp" # with "name" (CQLString "some name") # where' "empID" (104::Int64) # and' "deptID" (15::Int32)) <>
            batch (update "demodb.emp" # with "alive" False # where' "empID" (104::Int64) # and' "deptID" (15::Int32)) <>
            prepBatch p [
                        put (101::Int64),
                        put (13::Int32),
                        put True,
                        put $ fromJust $ fromString "48d0ceb1-9e3e-427c-bc36-0106398f672b",
                        put $ CQLString "Hot1 Shot1",
                        put $ CQLDouble 10000.0]
      runBatch q

      --drop a table
      let q = drop' "table demodb.emp"
      runCQL LOCAL_ONE q

      --drop a keyspace
      let q = drop' "keyspace demodb"
      runCQL LOCAL_ONE q

    print res