Merge pull request #25 from VictorDenisov/master

Handle the case when mongodb returns less documents than cursor reque…

Database/MongoDB/Query.hs

@@ -63,6 +63,8 @@ import Control.Concurrent.MVar.Lifted (MVar, newMVar, mkWeakMVar,
 import Control.Concurrent.MVar.Lifted (MVar, newMVar, addMVarFinalizer,
                                          readMVar, modifyMVar)
 #endif
+import Control.Applicative ((<$>))
+import Control.Monad (when)
 import Control.Monad.Base (MonadBase)
 import Control.Monad.Error (Error(..))
 import Control.Monad.Reader (MonadReader, ReaderT, runReaderT, ask, asks, local)
@@ -505,7 +507,7 @@ distinct :: (MonadIO m) => Label -> Selection -> Action m [Value]
 -- ^ Fetch distinct values of field in selected documents
 distinct k (Select sel col) = at "values" `liftM` runCommand ["distinct" =: col, "key" =: k, "query" =: sel]
 
-queryRequest :: (Monad m) => Bool -> Query -> Action m (Request, Limit)
+queryRequest :: (Monad m) => Bool -> Query -> Action m (Request, Maybe Limit)
 -- ^ Translate Query to Protocol.Query. If first arg is true then add special $explain attribute.
 queryRequest isExplain Query{..} = do
     ctx <- ask
@@ -515,7 +517,7 @@ queryRequest isExplain Query{..} = do
         qOptions = readModeOption rm ++ options
         qFullCollection = db <.> coll selection
         qSkip = fromIntegral skip
-        (qBatchSize, remainingLimit) = batchSizeRemainingLimit batchSize limit
+        (qBatchSize, remainingLimit) = batchSizeRemainingLimit batchSize (if limit == 0 then Nothing else Just limit)
         qProjector = project
         mOrder = if null sort then Nothing else Just ("$orderby" =: sort)
         mSnapshot = if snapshot then Just ("$snapshot" =: True) else Nothing
@@ -524,29 +526,31 @@ queryRequest isExplain Query{..} = do
         special = catMaybes [mOrder, mSnapshot, mHint, mExplain]
         qSelector = if null special then s else ("$query" =: s) : special where s = selector selection
 
-batchSizeRemainingLimit :: BatchSize -> Limit -> (Int32, Limit)
+batchSizeRemainingLimit :: BatchSize -> (Maybe Limit) -> (Int32, Maybe Limit)
 -- ^ Given batchSize and limit return P.qBatchSize and remaining limit
-batchSizeRemainingLimit batchSize limit = if limit == 0
-    then (fromIntegral batchSize', 0)  -- no limit
-    else if 0 < batchSize' && batchSize' < limit
-        then (fromIntegral batchSize', limit - batchSize')
-        else (- fromIntegral limit, 1)
- where batchSize' = if batchSize == 1 then 2 else batchSize
-    -- batchSize 1 is broken because server converts 1 to -1 meaning limit 1
+batchSizeRemainingLimit batchSize mLimit =
+  let remaining =
+        case mLimit of
+          Nothing    -> batchSize
+          Just limit ->
+            if 0 < batchSize && batchSize < limit
+              then batchSize
+              else limit
+  in (fromIntegral remaining, mLimit)
 
 type DelayedBatch = IO Batch
 -- ^ A promised batch which may fail
 
-data Batch = Batch Limit CursorId [Document]
--- ^ CursorId = 0 means cursor is finished. Documents is remaining documents to serve in current batch. Limit is remaining limit for next fetch.
+data Batch = Batch (Maybe Limit) CursorId [Document]
+-- ^ CursorId = 0 means cursor is finished. Documents is remaining documents to serve in current batch. Limit is number of documents to return. Nothing means no limit.
 
-request :: (MonadIO m) => [Notice] -> (Request, Limit) -> Action m DelayedBatch
+request :: (MonadIO m) => [Notice] -> (Request, Maybe Limit) -> Action m DelayedBatch
 -- ^ Send notices and request and return promised batch
 request ns (req, remainingLimit) = do
     promise <- call ns req
     return $ fromReply remainingLimit =<< promise
 
-fromReply :: Limit -> Reply -> DelayedBatch
+fromReply :: Maybe Limit -> Reply -> DelayedBatch
 -- ^ Convert Reply to Batch or Failure
 fromReply limit Reply{..} = do
     mapM_ checkResponseFlag rResponseFlags
@@ -582,20 +586,31 @@ nextBatch :: (MonadIO m, MonadBaseControl IO m) => Cursor -> Action m [Document]
 -- ^ Return next batch of documents in query result, which will be empty if finished.
 nextBatch (Cursor fcol batchSize var) = modifyMVar var $ \dBatch -> do
     -- Pre-fetch next batch promise from server and return current batch.
-    Batch limit cid docs <- fulfill' fcol batchSize dBatch
-    dBatch' <- if cid /= 0 then nextBatch' fcol batchSize limit cid else return $ return (Batch 0 0 [])
-    return (dBatch', docs)
+    Batch mLimit cid docs <- fulfill' fcol batchSize dBatch
+    let newLimit = do
+              limit <- mLimit
+              return $ limit - (min limit $ fromIntegral $ length docs)
+    let emptyBatch = return $ Batch (Just 0) 0 []
+    let getNextBatch = nextBatch' fcol batchSize newLimit cid
+    let resultDocs = (maybe id (take . fromIntegral) mLimit) docs
+    case (cid, newLimit) of
+      (0, _)      -> return (emptyBatch, resultDocs)
+      (_, Just 0) -> do
+        send [KillCursors [cid]]
+        return (emptyBatch, resultDocs)
+      (_, _)      -> (, resultDocs) <$> getNextBatch
 
 fulfill' :: (MonadIO m) => FullCollection -> BatchSize -> DelayedBatch -> Action m Batch
 -- Discard pre-fetched batch if empty with nonzero cid.
 fulfill' fcol batchSize dBatch = do
     b@(Batch limit cid docs) <- fulfill dBatch
-    if cid /= 0 && null docs
+    if cid /= 0 && null docs && (limit > (Just 0))
         then nextBatch' fcol batchSize limit cid >>= fulfill
         else return b
 
-nextBatch' :: (MonadIO m) => FullCollection -> BatchSize -> Limit -> CursorId -> Action m DelayedBatch
-nextBatch' fcol batchSize limit cid = request [] (GetMore fcol batchSize' cid, remLimit)
+nextBatch' :: (MonadIO m) => FullCollection -> BatchSize -> (Maybe Limit) -> CursorId -> Action m DelayedBatch
+nextBatch' fcol batchSize limit cid = do
+    request [] (GetMore fcol batchSize' cid, remLimit)
     where (batchSize', remLimit) = batchSizeRemainingLimit batchSize limit
 
 next :: (MonadIO m, MonadBaseControl IO m) => Cursor -> Action m (Maybe Document)
@@ -604,16 +619,23 @@ next (Cursor fcol batchSize var) = modifyMVar var nextState where
     -- Pre-fetch next batch promise from server when last one in current batch is returned.
     -- nextState:: DelayedBatch -> Action m (DelayedBatch, Maybe Document)
     nextState dBatch = do
-        Batch limit cid docs <- fulfill' fcol batchSize dBatch
+        Batch mLimit cid docs <- fulfill' fcol batchSize dBatch
+        if mLimit == (Just 0)
+          then return (return $ Batch (Just 0) 0 [], Nothing)
+          else
             case docs of
                 doc : docs' -> do
-                dBatch' <- if null docs' && cid /= 0
-                    then nextBatch' fcol batchSize limit cid
-                    else return $ return (Batch limit cid docs')
+                    let newLimit = do
+                              limit <- mLimit
+                              return $ limit - 1
+                    dBatch' <- if null docs' && cid /= 0 && (newLimit > (Just 0))
+                        then nextBatch' fcol batchSize newLimit cid
+                        else return $ return (Batch newLimit cid docs')
+                    when (newLimit == (Just 0)) $ unless (cid == 0) $ send [KillCursors [cid]]
                     return (dBatch', Just doc)
                 [] -> if cid == 0
-                then return (return $ Batch 0 0 [], Nothing)  -- finished
-                else fmap (,Nothing) $ nextBatch' fcol batchSize limit cid
+                    then return (return $ Batch (Just 0) 0 [], Nothing)  -- finished
+                    else fmap (,Nothing) $ nextBatch' fcol batchSize mLimit cid
 
 nextN :: (MonadIO m, MonadBaseControl IO m) => Int -> Cursor -> Action m [Document]
 -- ^ Return next N documents or less if end is reached
@@ -627,7 +649,7 @@ closeCursor :: (MonadIO m, MonadBaseControl IO m) => Cursor -> Action m ()
 closeCursor (Cursor _ _ var) = modifyMVar var $ \dBatch -> do
     Batch _ cid _ <- fulfill dBatch
     unless (cid == 0) $ send [KillCursors [cid]]
-    return $ (return $ Batch 0 0 [], ())
+    return $ (return $ Batch (Just 0) 0 [], ())
 
 isCursorClosed :: (MonadIO m, MonadBase IO m) => Cursor -> Action m Bool
 isCursorClosed (Cursor _ _ var) = do
@@ -752,7 +774,7 @@ runMR mr = do
         Just (String coll) -> find $ query [] coll
         Just (Doc doc) -> useDb (at "db" doc) $ find $ query [] (at "collection" doc)
         Just x -> error $ "unexpected map-reduce result field: " ++ show x
-        Nothing -> newCursor "" "" 0 $ return $ Batch 0 0 (at "results" res)
+        Nothing -> newCursor "" "" 0 $ return $ Batch (Just 0) 0 (at "results" res)
 
 runMR' :: (MonadIO m) => MapReduce -> Action m MRResult
 -- ^ Run MapReduce and return a MR result document containing stats and the results if Inlined. Error if the map/reduce failed (because of bad Javascript).

mongoDB.cabal

@@ -67,6 +67,7 @@ test-suite test
                  -- now. It's too difficult to support old versions of GHC and
                  -- the new version of time.
                  , old-locale
+                 , text
                  , time
 
   default-language: Haskell2010

test/QuerySpec.hs

@@ -5,6 +5,8 @@ module QuerySpec (spec) where
 import TestImport
 import Control.Exception
 
+import qualified Data.Text as T
+
 testDBName :: Database
 testDBName = "mongodb-haskell-test"
 
@@ -122,6 +124,17 @@ spec = around withCleanDatabase $ do
       it "raises exception" $
         insertDuplicateWith insertAll_ `shouldThrow` anyException
 
+  describe "insertAll_" $ do
+    it "inserts documents and receives 100 000 of them" $ do
+      let docs = (flip map) [0..200000] $ \i ->
+              ["name" =: (T.pack $ "name " ++ (show i))]
+      db $ insertAll_ "bigCollection" docs
+      db $ do
+        cur <- find $ (select [] "bigCollection") {limit = 100000, batchSize = 100000}
+        returnedDocs <- rest cur
+
+        liftIO $ (length returnedDocs) `shouldBe` 100000
+
   describe "aggregate" $ do
     it "aggregates to normalize and sort documents" $ do
       db $ insertAll_ "users" [ ["_id" =: "jane", "joined" =: parseDate "2011-03-02", "likes" =: ["golf", "racquetball"]]