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Cursor nextBatch

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This commit is contained in:
Tony Hannan 2011-07-21 18:50:52 -04:00
parent 5e4a8aee3f
commit 58f83838de
1 changed files with 14 additions and 3 deletions
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17
Database/MongoDB/Query.hs
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@ -28,7 +28,7 @@ module Database.MongoDB.Query (
Query(..), QueryOption(NoCursorTimeout), Projector, Limit, Order, BatchSize,
explain, find, findOne, fetch, count, distinct,
-- *** Cursor
Cursor, next, nextN, rest, closeCursor, isCursorClosed,
Cursor, nextBatch, next, nextN, rest, closeCursor, isCursorClosed,
-- ** Group
Group(..), GroupKey(..), group,
-- ** MapReduce
@ -472,6 +472,17 @@ newCursor db col batchSize dBatch = do
addMVarFinalizer var (closeCursor cursor)
return cursor
nextBatch :: (MonadMVar 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 dBatch
dBatch' <- if cid /= 0 then nextBatch' limit cid else return $ return (Batch 0 0 [])
return (dBatch', docs)
where
nextBatch' limit cid = request [] (GetMore fcol batchSize' cid, remLimit)
where (batchSize', remLimit) = batchSizeRemainingLimit batchSize limit
next :: (MonadMVar m) => Cursor -> Action m (Maybe Document)
-- ^ Return next document in query result, or Nothing if finished.
next (Cursor fcol batchSize var) = modifyMVar var nextState where
@ -482,13 +493,13 @@ next (Cursor fcol batchSize var) = modifyMVar var nextState where
case docs of
doc : docs' -> do
dBatch' <- if null docs' && cid /= 0
then nextBatch limit cid
then nextBatch' limit cid
else return $ return (Batch limit cid docs')
return (dBatch', Just doc)
[] -> if cid == 0
then return (return $ Batch 0 0 [], Nothing) -- finished
else error $ "server returned empty batch but says more results on server"
nextBatch limit cid = request [] (GetMore fcol batchSize' cid, remLimit)
nextBatch' limit cid = request [] (GetMore fcol batchSize' cid, remLimit)
where (batchSize', remLimit) = batchSizeRemainingLimit batchSize limit
nextN :: (MonadMVar m, Functor m) => Int -> Cursor -> Action m [Document]