From 8f608c19552ef7bd6ce61af92496b3d5f5bf61b1 Mon Sep 17 00:00:00 2001
From: Gregor Kleen <gregor.kleen@ifi.lmu.de>
Date: Wed, 2 Sep 2020 21:25:20 +0200
Subject: [PATCH] feat(files): chunking

BREAKING CHANGE: files now chunked
---
 config/settings.yml                       |   1 +
 models/files.model                        |  20 +++-
 src/Crypto/Hash/Instances.hs              |   5 +
 src/Database/Esqueleto/Utils.hs           |  47 +++++++-
 src/Foundation/Type.hs                    |   3 +-
 src/Handler/Admin/Test/Download.hs        |   6 +-
 src/Handler/Sheet/PersonalisedFiles.hs    |   5 +-
 src/Handler/Submission/Download.hs        |   7 +-
 src/Handler/Utils.hs                      |  14 ++-
 src/Handler/Utils/Allocation.hs           |   2 +-
 src/Handler/Utils/Files.hs                |  86 +++++++++-----
 src/Handler/Utils/Form.hs                 |  27 +++--
 src/Handler/Utils/Mail.hs                 |   9 +-
 src/Handler/Utils/Rating.hs               |  14 +--
 src/Handler/Utils/Rating/Format.hs        |   7 +-
 src/Handler/Utils/Rating/Format/Legacy.hs |   6 +-
 src/Handler/Utils/Submission.hs           |   4 +-
 src/Handler/Utils/Zip.hs                  | 102 ++++++++--------
 src/Import/NoModel.hs                     |   2 +
 src/Jobs/Handler/Files.hs                 | 136 ++++++++++++++--------
 src/Model/Migration.hs                    |  15 ++-
 src/Model/Types/Common.hs                 |   2 -
 src/Model/Types/File.hs                   |  52 ++++++++-
 src/Settings.hs                           |   2 +
 src/Utils.hs                              |  27 ++++-
 src/Utils/Files.hs                        | 122 ++++++++++++++-----
 src/Utils/Sql.hs                          |  40 ++++++-
 test/Database/Fill.hs                     |   5 +-
 28 files changed, 546 insertions(+), 222 deletions(-)

diff --git a/config/settings.yml b/config/settings.yml
index 3824a9f2b..ee5a9a247 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -159,6 +159,7 @@ upload-cache:
   disable-cert-validation: "_env:UPLOAD_S3_DISABLE_CERT_VALIDATION:false"
 upload-cache-bucket: "uni2work-uploads"
 inject-files: 10
+file-upload-db-chunksize: 1048576 # 1MiB
 
 server-sessions:
   idle-timeout: 28807
diff --git a/models/files.model b/models/files.model
index 428331b36..2a8656a3e 100644
--- a/models/files.model
+++ b/models/files.model
@@ -1,9 +1,20 @@
-FileContent
+FileContentEntry
     hash              FileContentReference
+    ix                Natural
+    chunkHash         FileContentChunkId
+    UniqueFileContentEntry hash ix
+
+FileContentChunk
+    hash              FileContentChunkReference
     content           ByteString
-    unreferencedSince UTCTime Maybe
+    contentBased      Bool default=false -- For Migration
     Primary           hash
 
+FileContentChunkUnreferenced
+    hash              FileContentChunkId
+    since             UTCTime
+    UniqueFileContentChunkUnreferenced hash
+
 SessionFile
     content         FileContentReference Maybe
     touched         UTCTime
@@ -12,3 +23,8 @@ FileLock
     content         FileContentReference
     instance        InstanceId
     time            UTCTime
+
+FileChunkLock
+    hash            FileContentChunkReference
+    instance        InstanceId
+    time            UTCTime
\ No newline at end of file
diff --git a/src/Crypto/Hash/Instances.hs b/src/Crypto/Hash/Instances.hs
index 93bf63516..0be90af18 100644
--- a/src/Crypto/Hash/Instances.hs
+++ b/src/Crypto/Hash/Instances.hs
@@ -18,6 +18,8 @@ import Data.Aeson as Aeson
 
 import Control.Monad.Fail
 
+import Language.Haskell.TH.Syntax (Lift(liftTyped))
+import Instances.TH.Lift ()
 
 instance HashAlgorithm hash => PersistField (Digest hash) where
   toPersistValue = PersistByteString . convert
@@ -46,3 +48,6 @@ instance HashAlgorithm hash => FromJSON (Digest hash) where
 
 instance Hashable (Digest hash) where
   hashWithSalt s = (hashWithSalt s :: ByteString -> Int) . convert
+
+instance HashAlgorithm hash => Lift (Digest hash) where
+  liftTyped dgst = [||fromMaybe (error "Lifted digest has wrong length") $ digestFromByteString $$(liftTyped (convert dgst :: ByteString))||]
diff --git a/src/Database/Esqueleto/Utils.hs b/src/Database/Esqueleto/Utils.hs
index 23daf5679..7db0e3c39 100644
--- a/src/Database/Esqueleto/Utils.hs
+++ b/src/Database/Esqueleto/Utils.hs
@@ -6,6 +6,7 @@ module Database.Esqueleto.Utils
   , justVal, justValList
   , isJust
   , isInfixOf, hasInfix
+  , strConcat, substring
   , or, and
   , any, all
   , subSelectAnd, subSelectOr
@@ -39,7 +40,8 @@ import qualified Data.Set as Set
 import qualified Data.List as List
 import qualified Data.Foldable as F
 import qualified Database.Esqueleto as E
-import qualified Database.Esqueleto.Internal.Sql as E
+import qualified Database.Esqueleto.PostgreSQL as E
+import qualified Database.Esqueleto.Internal.Internal as E
 import Database.Esqueleto.Utils.TH
 
 import qualified Data.Text.Lazy as Lazy (Text)
@@ -96,6 +98,42 @@ hasInfix :: ( E.SqlString s1
          => E.SqlExpr (E.Value s2) -> E.SqlExpr (E.Value s1) -> E.SqlExpr (E.Value Bool)
 hasInfix = flip isInfixOf
 
+infixl 6 `strConcat`
+
+strConcat :: E.SqlString s
+          => E.SqlExpr (E.Value s) -> E.SqlExpr (E.Value s) -> E.SqlExpr (E.Value s)
+strConcat = E.unsafeSqlBinOp " || "
+
+substring :: ( E.SqlString str
+             , Num from, Num for
+             )
+          => E.SqlExpr (E.Value str)
+          -> E.SqlExpr (E.Value from)
+          -> E.SqlExpr (E.Value for)
+          -> E.SqlExpr (E.Value str)
+substring (E.ERaw p1 f1) (E.ERaw p2 f2) (E.ERaw p3 f3)
+  = E.ERaw E.Never $ \info ->
+      let (strTLB, strVals) = f1 info
+          (fromiTLB, fromiVals) = f2 info
+          (foriTLB, foriVals) = f3 info
+       in ( "SUBSTRING" <> E.parens (E.parensM p1 strTLB <> " FROM " <> E.parensM p2 fromiTLB <> " FOR " <> E.parensM p3 foriTLB)
+          , strVals <> fromiVals <> foriVals
+          )
+substring a b c = substring (construct a) (construct b) (construct c)
+    where construct :: E.SqlExpr (E.Value a) -> E.SqlExpr (E.Value a)
+          construct (E.ERaw p f)        = E.ERaw E.Parens $ \info ->
+            let (b1, vals) = f info
+                build ("?", [E.PersistList vals']) =
+                  (E.uncommas $ replicate (length vals') "?", vals')
+                build expr = expr
+             in  build (E.parensM p b1, vals)
+          construct (E.ECompositeKey f) =
+            E.ERaw E.Parens $ \info -> (E.uncommas $ f info, mempty)
+          construct (E.EAliasedValue i _) = 
+            E.ERaw E.Never $ E.aliasedValueIdentToRawSql i
+          construct (E.EValueReference i i') = 
+            E.ERaw E.Never $ E.valueReferenceToRawSql i i'
+
 and, or :: Foldable f => f (E.SqlExpr (E.Value Bool)) -> E.SqlExpr (E.Value Bool)
 and = F.foldr (E.&&.) true
 or = F.foldr (E.||.) false
@@ -111,8 +149,11 @@ all :: MonoFoldable f => (Element f -> E.SqlExpr (E.Value Bool)) -> f -> E.SqlEx
 all test = and . map test . otoList
 
 subSelectAnd, subSelectOr :: E.SqlQuery (E.SqlExpr (E.Value Bool)) -> E.SqlExpr (E.Value Bool)
-subSelectAnd q = E.subSelectUnsafe $ E.unsafeSqlFunction "bool_and" <$> q
-subSelectOr q = E.subSelectUnsafe $ E.unsafeSqlFunction "bool_or" <$> q
+subSelectAnd q = parens . E.subSelectUnsafe $ flip (E.unsafeSqlAggregateFunction "bool_and" E.AggModeAll) [] <$> q
+subSelectOr  q = parens . E.subSelectUnsafe $ flip (E.unsafeSqlAggregateFunction "bool_or"  E.AggModeAll) [] <$> q
+
+parens :: E.SqlExpr (E.Value a) -> E.SqlExpr (E.Value a)
+parens = E.unsafeSqlFunction ""
 
 
 -- Allow usage of Tuples as DbtRowKey, i.e. SqlIn instances for tuples
diff --git a/src/Foundation/Type.hs b/src/Foundation/Type.hs
index 5595127e8..5257f1c35 100644
--- a/src/Foundation/Type.hs
+++ b/src/Foundation/Type.hs
@@ -7,7 +7,7 @@ module Foundation.Type
   , _SessionStorageMemcachedSql, _SessionStorageAcid
   , SMTPPool
   , _appSettings', _appStatic, _appConnPool, _appSmtpPool, _appLdapPool, _appWidgetMemcached, _appHttpManager, _appLogger, _appLogSettings, _appCryptoIDKey, _appClusterID, _appInstanceID, _appJobState, _appSessionStore, _appSecretBoxKey, _appJSONWebKeySet, _appHealthReport
-  , DB, Form, MsgRenderer, MailM
+  , DB, Form, MsgRenderer, MailM, DBFile
   ) where
 
 import Import.NoFoundation
@@ -81,3 +81,4 @@ type DB = YesodDB UniWorX
 type Form x = Html -> MForm (HandlerFor UniWorX) (FormResult x, WidgetFor UniWorX ())
 type MsgRenderer = MsgRendererS UniWorX -- see Utils
 type MailM a = MailT (HandlerFor UniWorX) a
+type DBFile = File (YesodDB UniWorX)
diff --git a/src/Handler/Admin/Test/Download.hs b/src/Handler/Admin/Test/Download.hs
index dc02ae8e0..9bf85419d 100644
--- a/src/Handler/Admin/Test/Download.hs
+++ b/src/Handler/Admin/Test/Download.hs
@@ -80,12 +80,12 @@ testDownload = do
       sourceDBChunks :: ConduitT () Int DB ()
       sourceDBChunks = forever sourceDBFiles
                     .| C.mapM (\x -> x <$ $logDebugS "testDownload.sourceDBChunks" (tshow $ entityKey x))
-                    .| C.map ((length $!!) . fileContentContent . entityVal)
+                    .| C.map ((length $!!) . fileContentChunkContent . entityVal)
                     .| takeLimit dlMaxSize
         where
-          sourceDBFiles = E.selectSource . E.from $ \fileContent -> do
+          sourceDBFiles = E.selectSource . E.from $ \fileContentChunk -> do
             E.orderBy [E.asc $ E.random_ @Int64]
-            return fileContent
+            return fileContentChunk
 
           takeLimit n | n <= 0 = return ()
           takeLimit n = do
diff --git a/src/Handler/Sheet/PersonalisedFiles.hs b/src/Handler/Sheet/PersonalisedFiles.hs
index 362c73d29..dc29fb61f 100644
--- a/src/Handler/Sheet/PersonalisedFiles.hs
+++ b/src/Handler/Sheet/PersonalisedFiles.hs
@@ -195,7 +195,7 @@ sourcePersonalisedSheetFiles :: forall m.
                              -> Maybe SheetId
                              -> Maybe (Set UserId)
                              -> PersonalisedSheetFilesDownloadAnonymous
-                             -> ConduitT () (Either PersonalisedSheetFile File) (SqlPersistT m) ()
+                             -> ConduitT () (Either PersonalisedSheetFile DBFile) (SqlPersistT m) ()
 sourcePersonalisedSheetFiles cId mbsid mbuids anonMode = do
   (mbIdx, cIDKey) <- lift . newPersonalisedFilesKey $ maybe (Left cId) Right mbsid
   let
@@ -255,9 +255,10 @@ sourcePersonalisedSheetFiles cId mbsid mbuids anonMode = do
             , fileModified = courseParticipantRegistration
             }
         yieldM . fmap Right $ do
-          fileContent <- lift $ Just . toStrict <$> formatPersonalisedSheetFilesMeta anonMode cPart cID
+          fileContent' <- lift $ formatPersonalisedSheetFilesMeta anonMode cPart cID
           let fileTitle = (dirName <//>) . ensureExtension "yaml" . unpack . mr $ MsgPersonalisedSheetFilesMetaFilename cID
               fileModified = courseParticipantRegistration
+              fileContent = Just $ C.sourceLazy fileContent'
           return File{..}
         _dirCache %= Set.insert dirName
       whenIsJust mbPFile $ \(Entity _ pFile@PersonalisedSheetFile{..}) -> do
diff --git a/src/Handler/Submission/Download.hs b/src/Handler/Submission/Download.hs
index 99f2f4457..6d55dfa62 100644
--- a/src/Handler/Submission/Download.hs
+++ b/src/Handler/Submission/Download.hs
@@ -11,8 +11,6 @@ import Handler.Utils.Submission
 
 import qualified Data.Set as Set
 
-import qualified Data.Text.Encoding as Text
-
 import qualified Database.Esqueleto as E
 
 import qualified Data.Conduit.Combinators as Conduit
@@ -32,9 +30,8 @@ getSubDownloadR tid ssh csh shn cID (submissionFileTypeIsUpdate -> isUpdate) pat
 
   case isRating of
     True
-      | isUpdate -> runDB $ do
-          file <- runMaybeT $ lift . ratingFile cID =<< MaybeT (getRating submissionID)
-          maybe notFound (return . toTypedContent . Text.decodeUtf8) $ fileContent =<< file
+      | isUpdate -> maybe notFound sendThisFile <=< runDB . runMaybeT $ 
+          lift . ratingFile cID =<< MaybeT (getRating submissionID)
       | otherwise -> notFound
     False -> do
       let results = (.| Conduit.map entityVal) . E.selectSource . E.from $ \sf -> do
diff --git a/src/Handler/Utils.hs b/src/Handler/Utils.hs
index b2b99ac45..c4ddd7db3 100644
--- a/src/Handler/Utils.hs
+++ b/src/Handler/Utils.hs
@@ -34,11 +34,13 @@ import Control.Monad.Logger
 
 
 -- | Simply send a `File`-Value
-sendThisFile :: File -> Handler TypedContent
+sendThisFile :: DBFile -> Handler TypedContent
 sendThisFile File{..}
   | Just fileContent' <- fileContent = do
       setContentDisposition' . Just $ takeFileName fileTitle
-      return $ TypedContent (simpleContentType (mimeLookup $ pack fileTitle) <> "; charset=utf-8") (toContent fileContent')
+      let cType = simpleContentType (mimeLookup $ pack fileTitle) <> "; charset=utf-8"
+      respondSourceDB cType $
+        fileContent' .| Conduit.map toFlushBuilder
   | otherwise = sendResponseStatus noContent204 ()
 
 -- | Serve a single file, identified through a given DB query
@@ -46,7 +48,7 @@ serveOneFile :: forall file. HasFileReference file => ConduitT () file (YesodDB
 serveOneFile source = do
   results <- runDB . runConduit $ source .| Conduit.take 2 -- We don't need more than two files to make a decision below
   case results of
-    [file] -> sendThisFile =<< runDB (sourceFile' file)
+    [file] -> sendThisFile $ sourceFile' file
     []     -> notFound
     _other -> do
       $logErrorS "SFileR" "Multiple matching files found."
@@ -58,7 +60,7 @@ serveOneFile source = do
 serveSomeFiles :: forall file. HasFileReference file => FilePath -> ConduitT () file (YesodDB UniWorX) () -> Handler TypedContent
 serveSomeFiles archiveName source = serveSomeFiles' archiveName $ source .| C.map Left
 
-serveSomeFiles' :: forall file. HasFileReference file => FilePath -> ConduitT () (Either file File) (YesodDB UniWorX) () -> Handler TypedContent
+serveSomeFiles' :: forall file. HasFileReference file => FilePath -> ConduitT () (Either file DBFile) (YesodDB UniWorX) () -> Handler TypedContent
 serveSomeFiles' archiveName source = do
   (source', results) <- runDB $ runPeekN 2 source
 
@@ -66,7 +68,7 @@ serveSomeFiles' archiveName source = do
 
   case results of
     []         -> notFound
-    [file]     -> sendThisFile =<< either (runDB . sourceFile') return file
+    [file]     -> sendThisFile $ either sourceFile' id file
     _moreFiles -> do
       setContentDisposition' $ Just archiveName
       respondSourceDB typeZip $ do
@@ -79,7 +81,7 @@ serveSomeFiles' archiveName source = do
 serveZipArchive :: forall file. HasFileReference file => FilePath -> ConduitT () file (YesodDB UniWorX) () -> Handler TypedContent
 serveZipArchive archiveName source = serveZipArchive' archiveName $ source .| C.map Left
 
-serveZipArchive' :: forall file. HasFileReference file => FilePath -> ConduitT () (Either file File) (YesodDB UniWorX) () -> Handler TypedContent
+serveZipArchive' :: forall file. HasFileReference file => FilePath -> ConduitT () (Either file DBFile) (YesodDB UniWorX) () -> Handler TypedContent
 serveZipArchive' archiveName source = do
   (source', results) <- runDB $ runPeekN 1 source
 
diff --git a/src/Handler/Utils/Allocation.hs b/src/Handler/Utils/Allocation.hs
index 510e9fc70..db512e25a 100644
--- a/src/Handler/Utils/Allocation.hs
+++ b/src/Handler/Utils/Allocation.hs
@@ -276,7 +276,7 @@ storeAllocationResult :: AllocationId
                       -> (AllocationFingerprint, Set (UserId, CourseId), Seq MatchingLogRun)
                       -> DB ()
 storeAllocationResult allocId now (allocFp, allocMatchings, ppMatchingLog -> allocLog) = do
-  FileReference{..} <- sinkFile $ File "matchings.log" (Just $ encodeUtf8 allocLog) now
+  FileReference{..} <- sinkFile $ File "matchings.log" (Just . yield $ encodeUtf8 allocLog) now
   insert_ . AllocationMatching allocId allocFp now $ fromMaybe (error "allocation result stored without fileReferenceContent") fileReferenceContent
 
   doAllocation allocId now allocMatchings
diff --git a/src/Handler/Utils/Files.hs b/src/Handler/Utils/Files.hs
index 9400a9a4b..2375bd4e7 100644
--- a/src/Handler/Utils/Files.hs
+++ b/src/Handler/Utils/Files.hs
@@ -7,12 +7,13 @@ module Handler.Utils.Files
 import Import
 
 import qualified Data.Conduit.Combinators as C
+import qualified Data.Conduit.List as C (unfoldM)
 
 import Handler.Utils.Minio
 import qualified Network.Minio as Minio
 
-import qualified Data.ByteString.Base64.URL as Base64
-import qualified Data.ByteArray as ByteArray
+import qualified Database.Esqueleto as E
+import qualified Database.Esqueleto.Utils as E
 
 
 data SourceFilesException
@@ -22,36 +23,59 @@ data SourceFilesException
   deriving anyclass (Exception)
 
 
-sourceFiles :: ConduitT FileReference File (YesodDB UniWorX) ()
-sourceFiles = C.mapM sourceFile
+sourceFiles :: Monad m => ConduitT FileReference DBFile m ()
+sourceFiles = C.map sourceFile
 
-sourceFile :: FileReference -> DB File
-sourceFile FileReference{..} = do
-  mFileContent <- traverse get $ FileContentKey <$> fileReferenceContent
-  fileContent <- if
-    | is (_Just . _Nothing) mFileContent
-    , Just fileContentHash <- fileReferenceContent -- Not a restriction
-      -> maybeT (throwM SourceFilesContentUnavailable) $ do
-        let uploadName = decodeUtf8 . Base64.encodeUnpadded $ ByteArray.convert fileContentHash
-        uploadBucket <- getsYesod $ views appSettings appUploadCacheBucket
-        fmap Just . hoistMaybe <=< runAppMinio . runMaybeT $ do
-          objRes <- catchIfMaybeT minioIsDoesNotExist $ Minio.getObject uploadBucket uploadName Minio.defaultGetObjectOptions
-          lift . runConduit $ Minio.gorObjectStream objRes .| C.fold
-    | fmap (fmap fileContentHash) mFileContent /= fmap Just fileReferenceContent
-      -> throwM SourceFilesMismatchedHashes
-    | Just fileContent' <- fileContentContent <$> join mFileContent
-      -> return $ Just fileContent'
-    | otherwise
-      -> return Nothing
+sourceFile :: FileReference -> DBFile
+sourceFile FileReference{..} = File
+  { fileTitle = fileReferenceTitle
+  , fileModified = fileReferenceModified
+  , fileContent = toFileContent <$> fileReferenceContent
+  }
+  where
+    toFileContent fileReference
+      | fileReference == $$(liftTyped $ FileContentReference $$(emptyHash))
+      = return ()
+    toFileContent fileReference = do
+      inDB <- lift . E.selectExists . E.from $ \fileContentEntry -> E.where_ $ fileContentEntry E.^. FileContentEntryHash E.==. E.val fileReference
+      if
+        | inDB -> do
+            dbChunksize <- getsYesod $ view _appFileUploadDBChunksize
+            let retrieveChunk chunkHash = \case
+                  Nothing -> return Nothing
+                  Just start -> do
+                    chunk <- E.selectMaybe . E.from $ \fileContentChunk -> do
+                      E.where_ $ fileContentChunk E.^. FileContentChunkId E.==. E.val chunkHash
+                      return $ E.substring (fileContentChunk E.^. FileContentChunkContent) (E.val start) (E.val dbChunksize)
+                    case chunk of
+                      Nothing -> throwM SourceFilesContentUnavailable
+                      Just (E.Value c) -> return . Just . (c, ) $ if
+                        | olength c >= dbChunksize -> Just $ start + dbChunksize
+                        | otherwise                -> Nothing
+                chunkHashes = E.selectSource . E.from $ \fileContentEntry -> do
+                  E.where_ $ fileContentEntry E.^. FileContentEntryHash E.==. E.val fileReference
+                  E.orderBy [ E.asc $ fileContentEntry E.^. FileContentEntryIx ]
+                  return $ fileContentEntry E.^. FileContentEntryChunkHash
+            chunkHashes .| C.map E.unValue .| awaitForever (\chunkHash -> C.unfoldM (retrieveChunk chunkHash) $ Just (1 :: Int))
+        | otherwise -> do
+            chunkVar <- newEmptyTMVarIO
+            minioAsync <- lift . allocateLinkedAsync $
+              maybeT (throwM SourceFilesContentUnavailable) $ do
+                let uploadName = minioFileReference # fileReference
+                uploadBucket <- getsYesod $ views appSettings appUploadCacheBucket
+                hoistMaybe <=< runAppMinio . runMaybeT $ do
+                  objRes <- catchIfMaybeT minioIsDoesNotExist $ Minio.getObject uploadBucket uploadName Minio.defaultGetObjectOptions
+                  lift . runConduit $ Minio.gorObjectStream objRes .| C.mapM_ (atomically . putTMVar chunkVar . Just)
+                  atomically $ putTMVar chunkVar Nothing
+            let go = do
+                  mChunk <- atomically $ readTMVar chunkVar
+                  case mChunk of
+                    Nothing -> waitAsync minioAsync
+                    Just chunk -> yield chunk >> go
+             in go
 
-  return File
-    { fileTitle = fileReferenceTitle
-    , fileContent
-    , fileModified = fileReferenceModified
-    }
+sourceFiles' :: forall file m. (HasFileReference file, Monad m) => ConduitT file DBFile m ()
+sourceFiles' = C.map sourceFile'
 
-sourceFiles' :: forall file. HasFileReference file => ConduitT file File (YesodDB UniWorX) ()
-sourceFiles' = C.mapM sourceFile'
-
-sourceFile' :: forall file. HasFileReference file => file -> DB File
+sourceFile' :: forall file. HasFileReference file => file -> DBFile
 sourceFile' = sourceFile . view (_FileReference . _1)
diff --git a/src/Handler/Utils/Form.hs b/src/Handler/Utils/Form.hs
index 68f9f68a0..4be16133b 100644
--- a/src/Handler/Utils/Form.hs
+++ b/src/Handler/Utils/Form.hs
@@ -32,7 +32,7 @@ import Yesod.Form.Bootstrap3
 
 import Handler.Utils.Zip
 import qualified Data.Conduit.Combinators as C
-import qualified Data.Conduit.List as C (mapMaybe)
+import qualified Data.Conduit.List as C (mapMaybe, mapMaybeM)
 
 import qualified Database.Esqueleto as E
 import qualified Database.Esqueleto.Utils as E
@@ -831,7 +831,10 @@ pseudonymWordField = checkMMap doCheck id $ ciField & addDatalist (return $ mkOp
 
 
 uploadContents :: (MonadHandler m, HandlerSite m ~ UniWorX) => ConduitT FileReference ByteString m ()
-uploadContents = transPipe (liftHandler . runDB) sourceFiles .| C.mapMaybe fileContent
+uploadContents = transPipe (liftHandler . runDB) sourceFiles .| C.mapMaybeM fileContent'
+  where fileContent' f = runMaybeT $ do
+          File{fileContent = Just fc} <- return f
+          liftHandler . runDB . runConduit $ fc .| C.fold
 
 data FileFieldUserOption a = FileFieldUserOption
   { fieldOptionForce :: Bool
@@ -893,11 +896,21 @@ genericFileField mkOpts = Field{..}
         , Map.filter (views _3 $ (&&) <$> fieldOptionForce <*> fieldOptionDefault) fieldAdditionalFiles
         ]
 
-    handleUpload :: FileField -> Maybe Text -> ConduitT File FileReference (YesodDB UniWorX) ()
+    handleUpload :: FileField -> Maybe Text -> ConduitT (File Handler) FileReference (YesodDB UniWorX) ()
     handleUpload FileField{fieldMaxFileSize} mIdent
-      =    C.filter (\File{..} -> maybe (const True) (>) fieldMaxFileSize $ maybe 0 (fromIntegral . olength) fileContent)
-        .| sinkFiles
-        .| C.mapM mkSessionFile
+      = C.map (transFile liftHandler)
+     .| C.mapMaybeM (\f@File{..} -> maybeT (return $ Just f) $ do
+                        maxSize <- fromIntegral <$> hoistMaybe fieldMaxFileSize
+                        fc <- hoistMaybe fileContent
+                        let peekNE n = do
+                              str <- C.takeE n .| C.fold
+                              leftover str
+                              yield str
+                        (unsealConduitT -> fc', size) <- lift $ fc $$+ peekNE (succ maxSize) .| C.lengthE
+                        return . guardOn (size <= maxSize) $ f { fileContent = Just fc' }
+                    )
+     .| sinkFiles
+     .| C.mapM mkSessionFile
       where
         mkSessionFile fRef@FileReference{..} = fRef <$ do
           now <- liftIO getCurrentTime
@@ -924,7 +937,7 @@ genericFileField mkOpts = Field{..}
         doUnpack
           | fieldOptionForce fieldUnpackZips = fieldOptionDefault fieldUnpackZips
           | otherwise = unpackZips `elem` vals
-        handleFile :: FileInfo -> ConduitT () File Handler ()
+        handleFile :: FileInfo -> ConduitT () (File Handler) Handler ()
         handleFile
           | doUnpack  = receiveFiles
           | otherwise = yieldM . acceptFile
diff --git a/src/Handler/Utils/Mail.hs b/src/Handler/Utils/Mail.hs
index 85038a894..18785044c 100644
--- a/src/Handler/Utils/Mail.hs
+++ b/src/Handler/Utils/Mail.hs
@@ -12,9 +12,7 @@ import Handler.Utils.Files
 
 import qualified Data.CaseInsensitive as CI
 
-import qualified Data.ByteString.Lazy as LBS
-
-import qualified Data.Conduit.List as C
+import qualified Data.Conduit.Combinators as C
 
 import qualified Text.Pandoc as P
 
@@ -72,12 +70,13 @@ addFileDB :: ( MonadMail m
              , HandlerSite m ~ UniWorX
              ) => FileReference -> m (Maybe MailObjectId)
 addFileDB fRef = runMaybeT $ do
-  File{fileTitle = pack . takeBaseName -> fileName, fileContent = Just fileContent} <- lift . liftHandler . runDB $ sourceFile fRef
+  File{fileTitle = pack . takeBaseName -> fileName, fileContent = Just fileContent'} <- return $ sourceFile fRef
+  fileContent <- liftHandler . runDB . runConduit $ fileContent' .| C.sinkLazy
   lift . addPart $ do
     _partType .= decodeUtf8 (mimeLookup fileName)
     _partEncoding .= Base64
     _partDisposition .= AttachmentDisposition fileName
-    _partContent .= PartContent (LBS.fromStrict fileContent)
+    _partContent .= PartContent fileContent
     setMailObjectIdPseudorandom (fileName, fileContent) :: StateT Part (HandlerFor UniWorX) MailObjectId
 
 
diff --git a/src/Handler/Utils/Rating.hs b/src/Handler/Utils/Rating.hs
index 5a82c8921..ef65892b0 100644
--- a/src/Handler/Utils/Rating.hs
+++ b/src/Handler/Utils/Rating.hs
@@ -16,11 +16,9 @@ import Handler.Utils.DateTime (getDateTimeFormatter)
 
 import qualified Data.Text as Text
 
-import qualified Data.ByteString.Lazy as Lazy.ByteString
-
 import qualified Database.Esqueleto as E
 
-import qualified Data.Conduit.List as Conduit
+import qualified Data.Conduit.Combinators as C
 
 import Handler.Utils.Rating.Format
 
@@ -91,15 +89,16 @@ extensionRating = "txt"
 
 ratingFile :: ( MonadHandler m
               , HandlerSite m ~ UniWorX
+              , Monad m'
               )
-           => CryptoFileNameSubmission -> Rating -> m File
+           => CryptoFileNameSubmission -> Rating -> m (File m')
 ratingFile cID rating@Rating{ ratingValues = Rating'{..} } = do
   mr'@(MsgRenderer mr) <- getMsgRenderer
   dtFmt <- getDateTimeFormatter
   fileModified <- maybe (liftIO getCurrentTime) return ratingTime
   let
     fileTitle = ensureExtension extensionRating . unpack . mr $ MsgRatingFileTitle cID
-    fileContent = Just . Lazy.ByteString.toStrict $ formatRating mr' dtFmt cID rating
+    fileContent = Just . C.sourceLazy $ formatRating mr' dtFmt cID rating
   return File{..}
 
 type SubmissionContent = Either FileReference (SubmissionId, Rating')
@@ -107,13 +106,12 @@ type SubmissionContent = Either FileReference (SubmissionId, Rating')
 extractRatings :: ( MonadHandler m
                   , HandlerSite m ~ UniWorX
                   ) => ConduitT FileReference SubmissionContent m ()
-extractRatings = Conduit.mapM $ \fRef@FileReference{..} -> liftHandler $ do
+extractRatings = C.mapM $ \fRef@FileReference{..} -> liftHandler $ do
   msId <- isRatingFile fileReferenceTitle
   if
     | Just sId <- msId
     , isJust fileReferenceContent -> do
-        f <- runDB $ sourceFile fRef
-        (rating, cID) <- handle (throwM . RatingFileException fileReferenceTitle) $ parseRating f
+        (rating, cID) <- handle (throwM . RatingFileException fileReferenceTitle) . runDB . parseRating $ sourceFile fRef
         sId' <- traverse decrypt cID
         unless (maybe (const True) (==) sId' sId) $
           throwM $ RatingFileException fileReferenceTitle RatingSubmissionIDIncorrect
diff --git a/src/Handler/Utils/Rating/Format.hs b/src/Handler/Utils/Rating/Format.hs
index fd8ab2fb5..e7cd03568 100644
--- a/src/Handler/Utils/Rating/Format.hs
+++ b/src/Handler/Utils/Rating/Format.hs
@@ -35,6 +35,8 @@ import qualified System.FilePath.Cryptographic as Explicit
 
 import Control.Exception (ErrorCall(..))
 
+import qualified Data.Conduit.Combinators as C
+
 
 data PrettifyState
   = PrettifyInitial
@@ -195,8 +197,9 @@ instance ns ~ CryptoIDNamespace (CI FilePath) SubmissionId => YAML.FromYAML (May
          )
 
 
-parseRating :: MonadCatch m => File -> m (Rating', Maybe CryptoFileNameSubmission)
-parseRating f@File{ fileContent = Just (fromStrict -> input), .. } = handle onFailure . handle (throwM . RatingParseException) . handleIf isYAMLUnicodeError (\(ErrorCall msg) -> throwM $ RatingYAMLNotUnicode msg) $ do
+parseRating :: MonadCatch m => File m -> m (Rating', Maybe CryptoFileNameSubmission)
+parseRating f@File{ fileContent = Just input', .. } = handle onFailure . handle (throwM . RatingParseException) . handleIf isYAMLUnicodeError (\(ErrorCall msg) -> throwM $ RatingYAMLNotUnicode msg) $ do
+  input <- runConduit $ input' .| C.sinkLazy
   let evStream = YAML.Event.parseEvents input
       delimitDocument = do
         ev <- maybe (throwM RatingYAMLStreamTerminatedUnexpectedly) return =<< await
diff --git a/src/Handler/Utils/Rating/Format/Legacy.hs b/src/Handler/Utils/Rating/Format/Legacy.hs
index bd523d06a..c027e1b07 100644
--- a/src/Handler/Utils/Rating/Format/Legacy.hs
+++ b/src/Handler/Utils/Rating/Format/Legacy.hs
@@ -16,6 +16,8 @@ import qualified Data.ByteString.Lazy as Lazy (ByteString)
 
 import qualified Data.CaseInsensitive as CI
 
+import qualified Data.Conduit.Combinators as C
+
 
 import Text.Read (readEither)
 
@@ -55,9 +57,9 @@ formatRating cID Rating{ ratingValues = Rating'{..}, ..} = let
     ]
   in Lazy.Text.encodeUtf8 . (<> "\n") $ displayT doc
 
-parseRating :: MonadCatch m => File -> m Rating'
+parseRating :: MonadCatch m => File m -> m Rating'
 parseRating File{ fileContent = Just input, .. } = handle (throwM . RatingParseLegacyException) $ do
-  inputText <- either (throwM . RatingNotUnicode) return $ Text.decodeUtf8' input
+  inputText <- either (throwM . RatingNotUnicode) return . Text.decodeUtf8' =<< runConduit (input .| C.fold)
   let
     (headerLines', commentLines) = break (commentSep `Text.isInfixOf`) $ Text.lines inputText
     (reverse -> ratingLines, reverse -> _headerLines) = break (sep' `Text.isInfixOf`) $ reverse headerLines'
diff --git a/src/Handler/Utils/Submission.hs b/src/Handler/Utils/Submission.hs
index 13ac4d067..2dcac8f28 100644
--- a/src/Handler/Utils/Submission.hs
+++ b/src/Handler/Utils/Submission.hs
@@ -256,7 +256,7 @@ planSubmissions sid restriction = do
     maximumsBy f xs = flip Set.filter xs $ \x -> maybe True (((==) `on` f) x . maximumBy (comparing f)) $ fromNullable xs
 
 
-submissionFileSource :: SubmissionId -> ConduitT () File (YesodDB UniWorX) ()
+submissionFileSource :: SubmissionId -> ConduitT () DBFile (YesodDB UniWorX) ()
 submissionFileSource subId = E.selectSource (E.from $ submissionFileQuery subId)
                           .| C.map entityVal
                           .| sourceFiles'
@@ -319,7 +319,7 @@ submissionMultiArchive anonymous (Set.toList -> ids) = do
   setContentDisposition' $ Just ((addExtension `on` unpack) (mr archiveName) extensionZip)
   respondSource typeZip . (<* lift cleanup) . transPipe (runDBRunner dbrunner) $ do
     let
-      fileEntitySource' :: (Rating, Entity Submission, Maybe UTCTime, (SheetName,CourseShorthand,SchoolId,TermId,Bool)) -> ConduitT () File (YesodDB UniWorX) ()
+      fileEntitySource' :: (Rating, Entity Submission, Maybe UTCTime, (SheetName,CourseShorthand,SchoolId,TermId,Bool)) -> ConduitT () DBFile (YesodDB UniWorX) ()
       fileEntitySource' (rating, Entity submissionID Submission{}, subTime, (shn,csh,ssh,tid,sheetAnonymous)) = do
         cID <- encrypt submissionID
 
diff --git a/src/Handler/Utils/Zip.hs b/src/Handler/Utils/Zip.hs
index 255d8f93b..0b469bcdb 100644
--- a/src/Handler/Utils/Zip.hs
+++ b/src/Handler/Utils/Zip.hs
@@ -17,11 +17,6 @@ import Codec.Archive.Zip.Conduit.Types
 import Codec.Archive.Zip.Conduit.UnZip
 import Codec.Archive.Zip.Conduit.Zip
 
--- import qualified Data.ByteString.Lazy as Lazy (ByteString)
-import qualified Data.ByteString.Lazy as Lazy.ByteString
-
-import qualified Data.ByteString as ByteString
-
 import System.FilePath
 import Data.Time.LocalTime (localTimeToUTC, utcToLocalTime)
 
@@ -38,6 +33,8 @@ import Data.Encoding ( decodeStrictByteStringExplicit
 import Data.Encoding.CP437
 import qualified Data.Char as Char
 
+import Control.Monad.Trans.Cont
+
 
 typeZip :: ContentType
 typeZip = "application/zip"
@@ -53,49 +50,54 @@ instance Default ZipInfo where
     }
 
 
-consumeZip :: forall b m.
+consumeZip :: forall b m m'.
               ( MonadThrow b
               , MonadThrow m
               , MonadBase b m
               , PrimMonad b
+              , MonadUnliftIO m
+              , MonadResource m
+              , MonadIO m'
               )
-           => ConduitT ByteString File m ZipInfo
-consumeZip = transPipe liftBase unZipStream `fuseUpstream` consumeZip'
-  where
-    consumeZip' :: ConduitT (Either ZipEntry ByteString) File m ()
-    consumeZip' = do
-      input <- await
-      case input of
-        Nothing -> return ()
-        Just (Right _) -> throwM $ userError "Data chunk in unexpected place when parsing ZIP"
-        Just (Left ZipEntry{..}) -> do
-          contentChunks <- toConsumer accContents
-          zipEntryName' <- decodeZipEntryName zipEntryName
-          let
-            fileTitle = dropWhile isPathSeparator . dropTrailingPathSeparator . normalise $ makeValid zipEntryName'
-            fileModified = localTimeToUTC utc zipEntryTime
-            fileContent
-              | hasTrailingPathSeparator zipEntryName' = Nothing
-              | otherwise = Just $ mconcat contentChunks
-          yield File{..}
-          consumeZip'
-    accContents :: ConduitT (Either a b') Void m [b']
-    accContents = do
-      input <- await
-      case input of
-        Just (Right x) -> (x :) <$> accContents
-        Just (Left x)  -> []    <$ leftover (Left x)
-        _ -> return []
+           => ConduitT () ByteString m () -> ConduitT () (File m') m ZipInfo
+consumeZip inpBS = do
+  inps <- liftIO newBroadcastTMChanIO
+  let feedSingle inp = atomically $ do
+        guardM $ isEmptyTMChan inps
+        writeTMChan inps inp
+  zipAsync <- lift . allocateLinkedAsync . runConduit $ do
+    zipInfo <- (inpBS .| transPipe liftBase unZipStream) `fuseUpstream` C.mapM_ feedSingle
+    atomically $ closeTMChan inps
+    return zipInfo
 
-produceZip :: forall b m.
-            ( MonadThrow b
-            , MonadThrow m
-            , MonadBase b m
-            , PrimMonad b
+  evalContT . callCC $ \finish -> forever $ do
+    (fileChan, fileDef) <- atomically $ do
+      fileChan <- dupTMChan inps
+      fileDef <- readTMChan fileChan
+      return (fileChan, fileDef)
+    case fileDef of
+      Nothing -> finish =<< waitAsync zipAsync
+      Just (Right _) -> return ()
+      Just (Left ZipEntry{..}) -> do
+        zipEntryName' <- decodeZipEntryName zipEntryName
+        let
+          fileTitle = dropWhile isPathSeparator . dropTrailingPathSeparator . normalise $ makeValid zipEntryName'
+          fileModified = localTimeToUTC utc zipEntryTime
+          isDirectory = hasTrailingPathSeparator zipEntryName'
+          fileContent
+            | isDirectory = Nothing
+            | otherwise   = Just . evalContT . callCC $ \finishContent -> forever $ do
+                nextVal <- atomically $ (preview _Right =<<) <$> readTMChan fileChan
+                maybe (finishContent ()) (lift . yield) nextVal
+        lift $ yield File{..}
+
+produceZip :: forall m.
+            ( MonadThrow m
+            , PrimMonad m
             )
            => ZipInfo
-           -> ConduitT File ByteString m ()
-produceZip info = C.map toZipData .| transPipe liftBase (void $ zipStream zipOptions)
+           -> ConduitT (File m) ByteString m ()
+produceZip info = C.map toZipData .| void (zipStream zipOptions)
   where
     zipOptions = ZipOptions
       { zipOpt64 = True
@@ -103,13 +105,11 @@ produceZip info = C.map toZipData .| transPipe liftBase (void $ zipStream zipOpt
       , zipOptInfo = info
       }
 
-    toZipData :: File -> (ZipEntry, ZipData b)
-    toZipData f@File{..} =
-      let zData = maybe mempty (ZipDataByteString . Lazy.ByteString.fromStrict) fileContent
-          zEntry = (toZipEntry f){ zipEntrySize = fromIntegral . ByteString.length <$> fileContent }
-       in (zEntry, zData)
+    toZipData :: File m -> (ZipEntry, ZipData m)
+    toZipData f@File{..}
+       = (toZipEntry f, ) $ maybe mempty ZipDataSource fileContent
 
-    toZipEntry :: File -> ZipEntry
+    toZipEntry :: File m -> ZipEntry
     toZipEntry File{..} = ZipEntry{..}
       where
         isDir = isNothing fileContent
@@ -119,26 +119,26 @@ produceZip info = C.map toZipData .| transPipe liftBase (void $ zipStream zipOpt
         zipEntrySize = Nothing
         zipEntryExternalAttributes = Nothing
 
-modifyFileTitle :: Monad m => (FilePath -> FilePath) -> ConduitT File File m ()
+modifyFileTitle :: Monad m => (FilePath -> FilePath) -> ConduitT (File m') (File m') m ()
 modifyFileTitle f = mapC $ \x@File{..} -> x{ fileTitle = f fileTitle }
 
 -- Takes FileInfo and if it is a ZIP-Archive, extract files, otherwiese yield fileinfo
-receiveFiles :: (MonadLogger m, MonadResource m, MonadThrow m, MonadBase IO m) => FileInfo -> ConduitT () File m ()
+receiveFiles :: (MonadLogger m, MonadResource m, MonadThrow m, MonadBase IO m, MonadUnliftIO m, MonadResource m') => FileInfo -> ConduitT () (File m') m ()
 receiveFiles fInfo
     | ((==) `on` simpleContentType) mimeType typeZip = do
         $logInfoS "sourceFiles" "Unpacking ZIP"
-        fileSource fInfo .| void consumeZip
+        void . consumeZip $ fileSource fInfo
     | otherwise = do
         $logDebugS "sourceFiles" [st|Not unpacking file of type #{decodeUtf8 mimeType}|]
         yieldM $ acceptFile fInfo
   where
     mimeType = mimeLookup $ fileName fInfo
 
-acceptFile :: MonadResource m => FileInfo -> m File
+acceptFile :: (MonadResource m, MonadResource m') => FileInfo -> m (File m')
 acceptFile fInfo = do
   let fileTitle = dropWhile isPathSeparator . dropTrailingPathSeparator . normalise . unpack $ fileName fInfo
+      fileContent = Just $ fileSource fInfo
   fileModified <- liftIO getCurrentTime
-  fileContent <- fmap Just . runConduit $ fileSource fInfo .| foldC
   return File{..}
 
 
diff --git a/src/Import/NoModel.hs b/src/Import/NoModel.hs
index ed39106a0..7c03533a4 100644
--- a/src/Import/NoModel.hs
+++ b/src/Import/NoModel.hs
@@ -128,6 +128,8 @@ import Data.Proxy as Import (Proxy(..))
 
 import Data.List.PointedList as Import (PointedList)
 
+import Language.Haskell.TH.Syntax as Import (Lift(liftTyped))
+
 import Language.Haskell.TH.Instances as Import ()
 import Data.NonNull.Instances as Import ()
 import Data.Monoid.Instances  as Import ()
diff --git a/src/Jobs/Handler/Files.hs b/src/Jobs/Handler/Files.hs
index 77e6337e2..48c4af882 100644
--- a/src/Jobs/Handler/Files.hs
+++ b/src/Jobs/Handler/Files.hs
@@ -9,20 +9,15 @@ import Import hiding (matching)
 import Database.Persist.Sql (deleteWhereCount)
 
 import qualified Database.Esqueleto as E
+import qualified Database.Esqueleto.PostgreSQL as E
 import qualified Database.Esqueleto.Utils as E
-import qualified Database.Esqueleto.Internal.Sql as E (unsafeSqlCastAs)
 
 import qualified Data.Conduit.Combinators as C
-import qualified Data.Conduit.List as C (mapMaybe)
+import qualified Data.Conduit.List as C (mapMaybe, unfoldM)
 
 import Handler.Utils.Minio
 import qualified Network.Minio as Minio
 
-import qualified Crypto.Hash as Crypto
-import qualified Data.ByteString.Base64.URL as Base64
-
-import Control.Monad.Memo (startEvalMemoT, memo)
-
 
 dispatchJobPruneSessionFiles :: JobHandler UniWorX
 dispatchJobPruneSessionFiles = JobHandlerAtomic  . hoist lift $ do
@@ -44,6 +39,9 @@ fileReferences (E.just -> fHash)
     , E.from $ \subFile   -> E.where_ $ subFile   E.^. SubmissionFileContent           E.==. fHash
     , E.from $ \sessFile  -> E.where_ $ sessFile  E.^. SessionFileContent              E.==. fHash
     , E.from $ \lock      -> E.where_ $ E.just (lock E.^. FileLockContent)             E.==. fHash
+    , E.from $ \chunkLock -> E.where_ . E.exists . E.from $ \fileContentEntry ->
+        E.where_ $ E.just (fileContentEntry E.^. FileContentEntryHash) E.==. fHash
+             E.&&. chunkLock E.^. FileChunkLockHash E.==. E.subSelectForeign fileContentEntry FileContentEntryChunkHash (E.^. FileContentChunkHash)
     ]
 
 
@@ -53,63 +51,111 @@ dispatchJobPruneUnreferencedFiles = JobHandlerAtomic . hoist lift $ do
   now <- liftIO getCurrentTime
   interval <- fmap (fmap $ max 0) . getsYesod $ view _appPruneUnreferencedFiles
   keep <- fmap (max 0) . getsYesod $ view _appKeepUnreferencedFiles
+  
+  E.insertSelectWithConflict
+    (UniqueFileContentChunkUnreferenced $ error "insertSelectWithConflict inspected constraint")
+    (E.from $ \fileContentChunk -> do
+        E.where_ . E.not_ . E.subSelectOr . E.from $ \fileContentEntry -> do
+          E.where_ $ fileContentEntry E.^. FileContentEntryChunkHash E.==. fileContentChunk E.^. FileContentChunkId
+          return . E.any E.exists . fileReferences $ fileContentEntry E.^. FileContentEntryHash
+        return $ FileContentChunkUnreferenced E.<# (fileContentChunk E.^. FileContentChunkId) E.<&> E.val now
+    )
+    (\current excluded ->
+        [ FileContentChunkUnreferencedSince E.=. E.min (current E.^. FileContentChunkUnreferencedSince) (excluded E.^. FileContentChunkUnreferencedSince) ]
+    )
 
-  E.update $ \fileContent -> do
-    let isReferenced = E.any E.exists . fileReferences $ fileContent E.^. FileContentHash
-        now' = E.unsafeSqlCastAs "TIMESTAMP WITH TIME ZONE" $ E.val now
-        shouldBe = E.bool (E.just . E.maybe now' (E.min now') $ fileContent E.^. FileContentUnreferencedSince) E.nothing isReferenced
-    E.set fileContent [ FileContentUnreferencedSince E.=. shouldBe ]
+  E.delete . E.from $ \fileContentChunkUnreferenced ->
+    E.where_ . E.subSelectOr . E.from $ \fileContentEntry -> do
+      E.where_ $ fileContentEntry E.^. FileContentEntryChunkHash E.==. fileContentChunkUnreferenced E.^. FileContentChunkUnreferencedHash
+      return . E.any E.exists . fileReferences $ fileContentEntry E.^. FileContentEntryHash
 
   let
-    getCandidates = E.selectSource . E.from $ \fileContent -> do
-      E.where_ . E.maybe E.false (E.<. E.val (addUTCTime (-keep) now)) $ fileContent E.^. FileContentUnreferencedSince
-      return ( fileContent E.^. FileContentHash
-             , E.length_ $ fileContent E.^. FileContentContent
+    getEntryCandidates = E.selectSource . E.from $ \fileContentEntry -> do
+      let unreferencedSince = E.subSelectMaybe . E.from $ \(fileContentEntry' `E.InnerJoin` fileContentChunkUnreferenced) -> do
+            E.on $ fileContentEntry' E.^. FileContentEntryChunkHash E.==. fileContentChunkUnreferenced E.^. FileContentChunkUnreferencedHash
+            E.where_ $ fileContentEntry' E.^. FileContentEntryHash E.==. fileContentEntry E.^. FileContentEntryHash
+            return . E.max_ $ fileContentChunkUnreferenced E.^. FileContentChunkUnreferencedSince
+      E.where_ $ E.maybe E.false (E.<. E.val (addUTCTime (-keep) now)) unreferencedSince
+
+      E.groupBy $ fileContentEntry E.^. FileContentEntryHash
+      E.orderBy [ E.asc $ fileContentEntry E.^. FileContentEntryHash ]
+    
+      return $ fileContentEntry E.^. FileContentEntryHash
+
+    deleteEntry :: _ -> DB (Sum Natural)
+    deleteEntry (E.Value fRef) =
+      bool 0 1 . (> 0) <$> deleteWhereCount [FileContentEntryHash ==. fRef]
+      
+  Sum deletedEntries <- runConduit $
+       getEntryCandidates
+    .| maybe (C.map id) (takeWhileTime . (/ 3)) interval
+    .| C.mapM deleteEntry
+    .| C.fold
+  
+  when (deletedEntries > 0) $
+    $logInfoS "PruneUnreferencedFiles" [st|Deleted #{tshow deletedEntries} long-unreferenced files|]
+  
+  let
+    getChunkCandidates = E.selectSource . E.from $ \fileContentChunkUnreferenced -> do
+      E.where_ $ fileContentChunkUnreferenced E.^. FileContentChunkUnreferencedSince E.<. E.val (addUTCTime (-keep) now)
+      E.where_ . E.not_ . E.exists . E.from $ \fileContentEntry ->
+        E.where_ $ fileContentEntry E.^. FileContentEntryChunkHash E.==. fileContentChunkUnreferenced E.^. FileContentChunkUnreferencedHash
+
+      return ( fileContentChunkUnreferenced E.^. FileContentChunkUnreferencedHash
+             , E.subSelectForeign fileContentChunkUnreferenced FileContentChunkUnreferencedHash $ E.length_ . (E.^. FileContentChunkContent)
              )
 
-  Sum deleted <- runConduit $
-       getCandidates
-    .| maybe (C.map id) (takeWhileTime . (/ 2)) interval
+    deleteChunk :: _ -> DB (Sum Natural, Sum Word64)
+    deleteChunk (E.Value cRef, E.Value size) = do
+      deleteWhere [ FileContentChunkUnreferencedHash ==. cRef ]
+      (, Sum size) . fromIntegral <$> deleteWhereCount [FileContentChunkHash ==. unFileContentChunkKey cRef]
+
+  (Sum deletedChunks, Sum deletedChunkSize) <- runConduit $
+       getChunkCandidates
+    .| maybe (C.map id) (takeWhileTime . (/ 3)) interval
     .| persistentTokenBucketTakeC' TokenBucketPruneFiles (view $ _2 . _Value :: _ -> Word64)
-    .| C.map (view $ _1 . _Value)
-    .| C.mapM (\fRef -> Sum <$> deleteWhereCount [FileContentHash ==. fRef])
+    .| C.mapM deleteChunk
     .| C.fold
-  when (deleted > 0) $
-    $logInfoS "PruneUnreferencedFiles" [st|Deleted #{deleted} long-unreferenced files|]
+
+  when (deletedChunks > 0) $
+    $logInfoS "PruneUnreferencedFiles" [st|Deleted #{tshow deletedChunks} chunks (#{tshow deletedChunkSize} bytes)|]
 
 
 dispatchJobInjectFiles :: JobHandler UniWorX
 dispatchJobInjectFiles = JobHandlerException . maybeT (return ()) $ do
   uploadBucket <- getsYesod $ view _appUploadCacheBucket
   interval <- getsYesod $ view _appInjectFiles
-  now <- liftIO getCurrentTime
 
   let
-    extractReference (Minio.ListItemObject oi)
-      | Right bs <- Base64.decodeUnpadded . encodeUtf8 $ Minio.oiObject oi
-      , Just fRef <- Crypto.digestFromByteString bs
-      = Just (oi, fRef)
+    extractReference (Minio.ListItemObject oi) = (oi, ) <$> Minio.oiObject oi ^? minioFileReference
     extractReference _ = Nothing
 
     injectOrDelete :: (Minio.Object, FileContentReference)
-                   -> Handler (Sum Int64, Sum Int64) -- ^ Injected, Already existed
-    injectOrDelete (obj, fRef) = maybeT (return mempty) $ do
-      res <- hoist (startEvalMemoT . hoistStateCache (runDB . setSerializable)) $ do
-        alreadyInjected <- lift . lift $ exists [ FileContentHash ==. fRef ]
-        if | alreadyInjected -> return (mempty, Sum 1)
-           | otherwise -> do
-               content <- flip memo obj $ \obj' -> hoistMaybeM . runAppMinio . runMaybeT $ do
-                 objRes <- catchIfMaybeT minioIsDoesNotExist $ Minio.getObject uploadBucket obj' Minio.defaultGetObjectOptions
-                 lift . runConduit $ Minio.gorObjectStream objRes .| C.fold
+                   -> Handler (Sum Int64) -- ^ Injected
+    injectOrDelete (obj, fRef) = do
+      fRef' <- runDB . setSerializable $ do
+        chunkVar <- newEmptyTMVarIO
+        dbAsync <- allocateLinkedAsync $ do
+          atomically $ isEmptyTMVar chunkVar >>= guard . not
+          sinkFileDB $ C.unfoldM (\x -> fmap (, x) <$> atomically (takeTMVar chunkVar)) ()
 
-               fmap ((, mempty) . Sum) . lift. lift . E.insertSelectCount $
-                 let isReferenced = E.any E.exists $ fileReferences (E.val fRef)
-                     now' = E.unsafeSqlCastAs "TIMESTAMP WITH TIME ZONE" $ E.val now
-                  in return $ FileContent E.<# E.val fRef E.<&> E.val content E.<&> E.bool (E.just now') E.nothing isReferenced
-      runAppMinio . maybeT (return ()) . catchIfMaybeT minioIsDoesNotExist $ Minio.removeObject uploadBucket obj
-      return res
+        didSend <- maybeT (return False) . hoistMaybeM . runAppMinio . runMaybeT $ do
+          objRes <- catchIfMaybeT minioIsDoesNotExist $ Minio.getObject uploadBucket obj Minio.defaultGetObjectOptions
+          lift . runConduit $ Minio.gorObjectStream objRes .| C.mapM_ (atomically . putTMVar chunkVar . Just)
+          return True
+        if
+          | not didSend -> Nothing <$ cancel dbAsync
+          | otherwise -> do
+              atomically $ putTMVar chunkVar Nothing
+              Just <$> waitAsync dbAsync
+      let matchesFRef = is _Just $ assertM (== fRef) fRef'
+      if | matchesFRef ->
+             maybeT (return ()) . runAppMinio . handleIf minioIsDoesNotExist (const $ return ()) $ Minio.removeObject uploadBucket obj
+         | otherwise ->
+             $logErrorS "InjectFiles" [st|Minio object “#{obj}”'s content does not match it's name (content hash: #{tshow fRef'} /= name hash: #{tshow fRef})|]
+      return . bool mempty (Sum 1) $ is _Just fRef'
 
-  (Sum inj, Sum exc) <-
+  Sum inj <-
     runConduit $ transPipe runAppMinio (Minio.listObjects uploadBucket Nothing True)
               .| C.mapMaybe extractReference
               .| maybe (C.map id) (takeWhileTime . (/ 2)) interval
@@ -118,7 +164,5 @@ dispatchJobInjectFiles = JobHandlerException . maybeT (return ()) $ do
               .| transPipe lift (C.mapM injectOrDelete)
               .| C.fold
 
-  when (exc > 0) $
-    $logInfoS "InjectFiles" [st|Deleted #{exc} files from upload cache because they were already injected|]
   when (inj > 0) $
     $logInfoS "InjectFiles" [st|Injected #{inj} files from upload cache into database|]
diff --git a/src/Model/Migration.hs b/src/Model/Migration.hs
index 711fffde2..e52ecd577 100644
--- a/src/Model/Migration.hs
+++ b/src/Model/Migration.hs
@@ -915,13 +915,26 @@ customMigrations = Map.fromListWith (>>)
 
     )
   , ( AppliedMigrationKey [migrationVersion|39.0.0|] [version|40.0.0|]
-    , whenM (tableExists "study_features") $ do
+    , whenM (tableExists "study_features") $
         [executeQQ|
           ALTER TABLE study_features RENAME updated TO last_observed;
           ALTER TABLE study_features ADD COLUMN first_observed timestamp with time zone;
           UPDATE study_features SET first_observed = (SELECT MAX(last_observed) FROM study_features as other WHERE other."user" = study_features."user" AND other.degree = study_features.degree AND other.field = study_features.field AND other.type = study_features.type AND other.semester = study_features.semester - 1);
         |]
     )
+  , ( AppliedMigrationKey [migrationVersion|40.0.0|] [version|41.0.0|]
+    , whenM (tableExists "file_content") $
+        [executeQQ|
+          ALTER TABLE file_content RENAME TO file_content_chunk;
+
+          CREATE TABLE file_content_chunk_unreferenced (id bigserial, hash bytea NOT NULL, since timestamp with time zone NOT NULL);
+          INSERT INTO file_content_chunk_unreferenced (since, hash) (SELECT unreferenced_since as since, hash FROM file_content_chunk WHERE NOT (unreferenced_since IS NULL));
+          ALTER TABLE file_content_chunk_chunk DROP COLUMN unreferenced_since;
+
+          CREATE TABLE file_content_entry (hash bytea NOT NULL, ix bigint NOT NULL, chunk_hash bytea NOT NULL);
+          INSERT INTO file_content_entry (hash, chunk_hash, ix) (SELECT hash, hash as chunk_hash, 0 as ix FROM file_content_chunk);
+        |]
+    )
   ]
 
 
diff --git a/src/Model/Types/Common.hs b/src/Model/Types/Common.hs
index ceb97f2a2..08783669c 100644
--- a/src/Model/Types/Common.hs
+++ b/src/Model/Types/Common.hs
@@ -54,5 +54,3 @@ type InstanceId              = UUID
 type ClusterId               = UUID
 type TokenId                 = UUID
 type TermCandidateIncidence  = UUID
-
-type FileContentReference    = Digest SHA3_512
diff --git a/src/Model/Types/File.hs b/src/Model/Types/File.hs
index 33bdadbb7..27855ce2b 100644
--- a/src/Model/Types/File.hs
+++ b/src/Model/Types/File.hs
@@ -1,23 +1,65 @@
 module Model.Types.File
-  ( File(..), _fileTitle, _fileContent, _fileModified
+  ( FileContentChunkReference(..), FileContentReference(..)
+  , File(..), _fileTitle, _fileContent, _fileModified
+  , transFile
+  , minioFileReference
   , FileReference(..), _fileReferenceTitle, _fileReferenceContent, _fileReferenceModified
   , HasFileReference(..), IsFileReference(..), FileReferenceResidual(..)
   ) where
 
 import Import.NoModel
-import Model.Types.Common (FileContentReference)
+   
+import Database.Persist.Sql (PersistFieldSql)
+import Web.HttpApiData (ToHttpApiData, FromHttpApiData)
+import Data.ByteArray (ByteArrayAccess)
+
+import qualified Data.ByteString.Base64.URL as Base64
+import qualified Data.ByteArray as ByteArray
+import qualified Network.Minio as Minio (Object)
+import qualified Crypto.Hash as Crypto (digestFromByteString)
 
 import Utils.Lens.TH
 
 
-data File = File
+
+newtype FileContentChunkReference = FileContentChunkReference (Digest SHA3_512)
+  deriving (Eq, Ord, Read, Show, Lift, Generic, Typeable)
+  deriving newtype ( PersistField, PersistFieldSql
+                   , PathPiece, ToHttpApiData, FromHttpApiData, ToJSON, FromJSON
+                   , Hashable, NFData
+                   , ByteArrayAccess
+                   )
+
+makeWrapped ''FileContentChunkReference
+
+newtype FileContentReference = FileContentReference (Digest SHA3_512)
+  deriving (Eq, Ord, Read, Show, Lift, Generic, Typeable)
+  deriving newtype ( PersistField, PersistFieldSql
+                   , PathPiece, ToHttpApiData, FromHttpApiData, ToJSON, FromJSON
+                   , Hashable, NFData
+                   , ByteArrayAccess
+                   )
+
+makeWrapped ''FileContentReference
+
+
+minioFileReference :: Prism' Minio.Object FileContentReference
+minioFileReference = prism' toObjectName fromObjectName
+  where toObjectName = decodeUtf8 . Base64.encodeUnpadded . ByteArray.convert
+        fromObjectName = fmap (review _Wrapped) . Crypto.digestFromByteString <=< preview _Right . Base64.decodeUnpadded . encodeUtf8
+  
+
+data File m = File
   { fileTitle    :: FilePath
-  , fileContent  :: Maybe ByteString
+  , fileContent  :: Maybe (ConduitT () ByteString m ())
   , fileModified :: UTCTime
-  } deriving (Eq, Ord, Read, Show, Generic, Typeable)
+  } deriving (Generic, Typeable)
 
 makeLenses_ ''File
 
+transFile :: Monad m => (forall a. m a -> n a) -> (File m -> File n)
+transFile l File{..} = File{ fileContent = transPipe l <$> fileContent, .. }
+
 data FileReference = FileReference
   { fileReferenceTitle    :: FilePath
   , fileReferenceContent  :: Maybe FileContentReference
diff --git a/src/Settings.hs b/src/Settings.hs
index 56bead944..3dffc78b4 100644
--- a/src/Settings.hs
+++ b/src/Settings.hs
@@ -172,6 +172,7 @@ data AppSettings = AppSettings
     , appUploadCacheConf        :: Maybe Minio.ConnectInfo
     , appUploadCacheBucket      :: Minio.Bucket
     , appInjectFiles            :: Maybe NominalDiffTime
+    , appFileUploadDBChunksize  :: Int
 
     , appFavouritesQuickActionsBurstsize
     , appFavouritesQuickActionsAvgInverseRate :: Word64
@@ -474,6 +475,7 @@ instance FromJSON AppSettings where
         appPruneUnreferencedFiles <- o .:? "prune-unreferenced-files"
         appKeepUnreferencedFiles  <- o .:? "keep-unreferenced-files" .!= 0
         appInjectFiles            <- o .:? "inject-files"
+        appFileUploadDBChunksize  <- o .:  "file-upload-db-chunksize"
 
         appMaximumContentLength   <- o .: "maximum-content-length"
 
diff --git a/src/Utils.hs b/src/Utils.hs
index 3a517d231..5f25e1ac3 100644
--- a/src/Utils.hs
+++ b/src/Utils.hs
@@ -56,7 +56,8 @@ import Control.Arrow as Utils ((>>>))
 import Control.Monad.Trans.Except (ExceptT(..), throwE, runExceptT)
 import Control.Monad.Except (MonadError(..))
 import Control.Monad.Trans.Maybe as Utils (MaybeT(..))
-import Control.Monad.Trans.Writer.Lazy (WriterT, execWriterT, tell)
+import Control.Monad.Trans.Writer.Strict (execWriterT)
+import Control.Monad.Writer.Class (MonadWriter(..))
 import Control.Monad.Catch
 import Control.Monad.Morph (hoist)
 import Control.Monad.Fail
@@ -83,6 +84,9 @@ import qualified Crypto.Saltine.Class as Saltine
 import qualified Crypto.Data.PKCS7 as PKCS7
 import Crypto.MAC.KMAC (KMAC, HashSHAKE)
 import qualified Crypto.MAC.KMAC as KMAC
+import qualified Crypto.Hash as Crypto
+import Crypto.Hash (HashAlgorithm, Digest)
+import Crypto.Hash.Instances ()
 
 import Data.ByteArray (ByteArrayAccess)
 
@@ -843,7 +847,7 @@ diffTimeout timeoutLength timeoutRes act = fromMaybe timeoutRes <$> timeout time
       = let (MkFixed micro :: Micro) = realToFrac timeoutLength
          in fromInteger micro
 
-tellM :: (Monad m, Monoid x) => m x -> WriterT x m ()
+tellM :: (MonadTrans t, MonadWriter x (t m), Monad m) => m x -> t m ()
 tellM = tell <=< lift
 
 -------------
@@ -856,6 +860,19 @@ peekN n = do
   mapM_ leftover peeked
   return peeked
 
+peekWhile :: forall a o m. Monad m => (a -> Bool) -> ConduitT a o m [a]
+peekWhile p = do
+  let go acc = do
+        next <- await
+        case next of
+          Nothing -> return (reverse acc, Nothing)
+          Just x
+            | p x       -> go $ x : acc
+            | otherwise -> return (reverse acc, Just x)
+  (peeked, failed) <- go []
+  mapM_ leftover $ peeked ++ hoistMaybe failed
+  return peeked
+
 anyMC, allMC :: forall a o m. Monad m => (a -> m Bool) -> ConduitT a o m Bool
 anyMC f = C.mapM f .| orC
 allMC f = C.mapM f .| andC
@@ -1057,6 +1074,12 @@ kmaclazy :: forall a string key ba chunk.
          -> KMAC a
 kmaclazy str k = KMAC.finalize . KMAC.updates (KMAC.initialize @a str k) . toChunks
 
+emptyHash :: forall a. HashAlgorithm a => Q (TExp (Digest a))
+-- ^ Hash of `mempty`
+--
+-- Computationally preferrable to computing the hash at runtime
+emptyHash = TH.liftTyped $ Crypto.hashFinalize Crypto.hashInit
+
 -------------
 -- Caching --
 -------------
diff --git a/src/Utils/Files.hs b/src/Utils/Files.hs
index 0138a93c4..fadc7f23d 100644
--- a/src/Utils/Files.hs
+++ b/src/Utils/Files.hs
@@ -3,6 +3,7 @@ module Utils.Files
   , sinkFile', sinkFiles'
   , FileUploads
   , replaceFileReferences, replaceFileReferences'
+  , sinkFileDB
   ) where
 
 import Import.NoFoundation
@@ -11,31 +12,46 @@ import Handler.Utils.Minio
 import qualified Network.Minio as Minio
 
 import qualified Crypto.Hash as Crypto (hash)
+import qualified Crypto.Hash.Conduit as Crypto (sinkHash)
 
 import qualified Data.Conduit.Combinators as C
-
-import qualified Data.ByteString.Base64.URL as Base64
-import qualified Data.ByteArray as ByteArray
+import qualified Data.Conduit.List as C (unfoldM)
 
 import qualified Data.Map.Lazy as Map
 import qualified Data.Set as Set
 import Control.Monad.State.Class (modify)
 
+import qualified Data.Sequence as Seq
+
 import Database.Persist.Sql (deleteWhereCount)
 
 import Control.Monad.Trans.Resource (allocate)
 
+import qualified Data.UUID.V4 as UUID
 
-sinkFiles :: (MonadThrow m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX) => ConduitT File FileReference (SqlPersistT m) ()
-sinkFiles = C.mapM sinkFile
+import qualified Database.Esqueleto as E
+import qualified Database.Esqueleto.Utils as E
+
+
+sinkFileDB :: (MonadCatch m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX)
+           => ConduitT () ByteString (SqlPersistT m) () -> SqlPersistT m FileContentReference
+sinkFileDB fileContentContent = do
+  dbChunksize <- getsYesod $ view _appFileUploadDBChunksize
+
+  let sinkChunk fileContentChunkContent = do
+        fileChunkLockTime <- liftIO getCurrentTime
+        fileChunkLockInstance <- getsYesod appInstanceID
+
+        tellM $ Set.singleton <$> insert FileChunkLock{ fileChunkLockHash = fileContentChunkHash, .. }
+        lift . handleIfSql isUniqueConstraintViolation (const $ return ()) $
+          insert_ FileContentChunk{..}
+        return $ FileContentChunkKey fileContentChunkHash
+        where fileContentChunkHash = _Wrapped # Crypto.hash fileContentChunkContent
+  ((review _Wrapped -> fileContentHash, fileContentChunks), chunkLocks) <- runConduit . runWriterC $ transPipe lift fileContentContent
+    .| C.chunksOfE dbChunksize
+    .| C.mapM (\c -> (c, ) <$> sinkChunk c)
+    .| transPipe lift (getZipConduit $ (,) <$> ZipConduit (C.map (view _1) .| Crypto.sinkHash) <*> ZipConduit (C.foldMap $ views _2 Seq.singleton))
 
-sinkFile :: (MonadThrow m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX) => File -> SqlPersistT m FileReference
-sinkFile File{ fileContent = Nothing, .. } = return FileReference
-  { fileReferenceContent  = Nothing
-  , fileReferenceTitle    = fileTitle
-  , fileReferenceModified = fileModified
-  }
-sinkFile File{ fileContent = Just fileContentContent, .. } = do
   void . withUnliftIO $ \UnliftIO{..} ->
     let takeLock = do
           fileLockTime <- liftIO getCurrentTime
@@ -44,35 +60,81 @@ sinkFile File{ fileContent = Just fileContentContent, .. } = do
         releaseLock lId = liftHandler . runDB $ (withReaderT projectBackend $ setSerializable (delete lId :: SqlPersistT (HandlerFor UniWorX) ()) :: YesodDB UniWorX ())
      in unliftIO $ allocate (unliftIO takeLock) (unliftIO . releaseLock)
 
-  inDB <- exists [ FileContentHash ==. fileContentHash ]
+  deleteWhere [ FileChunkLockId <-. Set.toList chunkLocks ]
 
-  let sinkFileDB = unless inDB $ repsert (FileContentKey fileContentHash) FileContent{ fileContentUnreferencedSince = Nothing, .. }
-  maybeT sinkFileDB $ do
-    let uploadName = decodeUtf8 . Base64.encodeUnpadded $ ByteArray.convert fileContentHash
-    uploadBucket <- getsYesod $ views appSettings appUploadCacheBucket
-    unless inDB . runAppMinio $ do
-      uploadExists <- handleIf minioIsDoesNotExist (const $ return False) $ True <$ Minio.statObject uploadBucket uploadName Minio.defaultGetObjectOptions
-      unless uploadExists $ do
-        let
-          pooOptions = Minio.defaultPutObjectOptions
-            { Minio.pooCacheControl = Just "immutable"
-            }
-        Minio.putObject uploadBucket uploadName (C.sourceLazy $ fromStrict fileContentContent) (Just . fromIntegral $ olength fileContentContent) pooOptions
-        -- Note that MinIO does not accept length zero uploads without an explicit length specification (not `Nothing` in the line above for the api we use)
+  let entryExists = E.selectExists . E.from $ \fileContentEntry -> E.where_ $ fileContentEntry E.^. FileContentEntryHash E.==. E.val fileContentHash
+  unlessM entryExists . void $
+    insertMany_ [ FileContentEntry{ fileContentEntryHash = fileContentHash, .. }
+                | fileContentEntryChunkHash <- otoList fileContentChunks
+                | fileContentEntryIx <- [0..]
+                ]
+
+  return fileContentHash
+  where fileContentChunkContentBased = False
+
+  
+sinkFiles :: (MonadCatch m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX) => ConduitT (File (SqlPersistT m)) FileReference (SqlPersistT m) ()
+sinkFiles = C.mapM sinkFile
+
+sinkFile :: (MonadCatch m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX) => File (SqlPersistT m) -> SqlPersistT m FileReference
+sinkFile File{ fileContent = Nothing, .. } = return FileReference
+  { fileReferenceContent  = Nothing
+  , fileReferenceTitle    = fileTitle
+  , fileReferenceModified = fileModified
+  }
+sinkFile File{ fileContent = Just fileContentContent, .. } = do
+  (unsealConduitT -> fileContentContent', isEmpty) <- fileContentContent $$+ is _Nothing <$> C.peekE
+
+  fileContentHash <- if
+    | not isEmpty -> maybeT (sinkFileDB fileContentContent') $ do
+        uploadBucket <- getsYesod $ views appSettings appUploadCacheBucket
+        chunk <- liftIO newEmptyMVar
+        let putChunks = do
+              nextChunk <- await
+              case nextChunk of
+                Nothing
+                  -> putMVar chunk Nothing
+                Just nextChunk'
+                  -> putMVar chunk (Just nextChunk') >> yield nextChunk' >> putChunks
+        sinkAsync <- lift . allocateLinkedAsync . runConduit
+           $ fileContentContent'
+          .| putChunks
+          .| Crypto.sinkHash
+
+        runAppMinio $ do
+          tmpUUID <- liftIO UUID.nextRandom
+          let uploadName = ".tmp." <> toPathPiece tmpUUID
+              pooOptions = Minio.defaultPutObjectOptions
+                { Minio.pooCacheControl = Just "immutable"
+                }
+          Minio.putObject uploadBucket uploadName (C.unfoldM (\x -> fmap (, x) <$> takeMVar chunk) ()) Nothing pooOptions
+          fileContentHash <- review _Wrapped <$> waitAsync sinkAsync
+          let dstName = minioFileReference # fileContentHash
+              copySrc = Minio.defaultSourceInfo
+                { Minio.srcBucket = uploadBucket, Minio.srcObject = uploadName
+                }
+              copyDst = Minio.defaultDestinationInfo
+                { Minio.dstBucket = uploadBucket
+                , Minio.dstObject = dstName
+                }
+          uploadExists <- handleIf minioIsDoesNotExist (const $ return False) $ True <$ Minio.statObject uploadBucket dstName Minio.defaultGetObjectOptions
+          unless uploadExists $ 
+            Minio.copyObject copyDst copySrc
+          Minio.removeObject uploadBucket uploadName
+          return fileContentHash
+    | otherwise -> return $$(liftTyped $ FileContentReference $$(emptyHash))
 
   return FileReference
     { fileReferenceContent  = Just fileContentHash
     , fileReferenceTitle    = fileTitle
     , fileReferenceModified = fileModified
     }
-  where
-    fileContentHash = Crypto.hash fileContentContent
 
 
-sinkFiles' :: (MonadThrow m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX, HasFileReference record) => ConduitT (File, FileReferenceResidual record) record (SqlPersistT m) ()
+sinkFiles' :: (MonadCatch m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX, HasFileReference record) => ConduitT (File (SqlPersistT m), FileReferenceResidual record) record (SqlPersistT m) ()
 sinkFiles' = C.mapM $ uncurry sinkFile'
 
-sinkFile' :: (MonadThrow m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX, HasFileReference record) => File -> FileReferenceResidual record -> SqlPersistT m record
+sinkFile' :: (MonadCatch m, MonadHandler m, HandlerSite m ~ UniWorX, MonadUnliftIO m, BackendCompatible SqlBackend (YesodPersistBackend UniWorX), YesodPersist UniWorX, HasFileReference record) => File (SqlPersistT m) -> FileReferenceResidual record -> SqlPersistT m record
 sinkFile' file residual = do
   reference <- sinkFile file
   return $ _FileReference # (reference, residual)
diff --git a/src/Utils/Sql.hs b/src/Utils/Sql.hs
index 2a03a76da..ad51820d0 100644
--- a/src/Utils/Sql.hs
+++ b/src/Utils/Sql.hs
@@ -1,22 +1,32 @@
 module Utils.Sql
   ( setSerializable, setSerializable'
+  , catchSql, handleSql
+  , isUniqueConstraintViolation
+  , catchIfSql, handleIfSql
   ) where
 
-import ClassyPrelude.Yesod
+import ClassyPrelude.Yesod hiding (handle)
 import Numeric.Natural
 import Settings.Log
 
-import Database.PostgreSQL.Simple (SqlError)
+import Database.PostgreSQL.Simple (SqlError(..))
 import Database.PostgreSQL.Simple.Errors (isSerializationError)
-import Control.Monad.Catch (MonadMask)
+import Control.Monad.Catch
 
 import Database.Persist.Sql
 import Database.Persist.Sql.Raw.QQ
 
+import qualified Data.ByteString as ByteString
+
 import Control.Retry
 
 import Control.Lens ((&))
 
+import qualified Data.UUID as UUID
+import Control.Monad.Random.Class (MonadRandom(getRandom))
+
+import Text.Shakespeare.Text (st)
+
 
 setSerializable :: forall m a. (MonadLogger m, MonadMask m, MonadIO m, ReadLogSettings (SqlPersistT m)) => SqlPersistT m a -> SqlPersistT m a
 setSerializable = setSerializable' $ fullJitterBackoff 1e3 & limitRetriesByCumulativeDelay 10e6
@@ -54,5 +64,29 @@ setSerializable' policy act = do
               transactionSaveWithIsolation ReadCommitted
               return res
 
+catchSql :: forall m a. (MonadCatch m, MonadIO m) => SqlPersistT m a -> (SqlError -> SqlPersistT m a) -> SqlPersistT m a
+catchSql = flip handleSql
 
+handleSql :: forall m a. (MonadCatch m, MonadIO m) => (SqlError -> SqlPersistT m a) -> SqlPersistT m a -> SqlPersistT m a
+handleSql recover act = do
+  savepointName <- liftIO $ UUID.toString <$> getRandom
 
+  let recover' :: SqlError -> SqlPersistT m a
+      recover' exc = do
+        rawExecute [st|ROLLBACK TO SAVEPOINT "#{savepointName}"|] []
+        recover exc
+  
+  handle recover' $ do
+    rawExecute [st|SAVEPOINT "#{savepointName}"|] []
+    res <- act
+    rawExecute [st|RELEASE SAVEPOINT "#{savepointName}"|] []
+    return res
+
+catchIfSql :: forall m a. (MonadCatch m, MonadIO m) => (SqlError -> Bool) -> SqlPersistT m a -> (SqlError -> SqlPersistT m a) -> SqlPersistT m a
+catchIfSql p = flip $ handleIfSql p
+  
+handleIfSql :: forall m a. (MonadCatch m, MonadIO m) => (SqlError -> Bool) -> (SqlError -> SqlPersistT m a) -> SqlPersistT m a -> SqlPersistT m a
+handleIfSql p recover = handleSql (\err -> bool throwM recover (p err) err)
+
+isUniqueConstraintViolation :: SqlError -> Bool
+isUniqueConstraintViolation SqlError{..} = "duplicate key value violates unique constraint" `ByteString.isPrefixOf` sqlErrorMsg
diff --git a/test/Database/Fill.hs b/test/Database/Fill.hs
index 4c1d4a3ee..0292308da 100644
--- a/test/Database/Fill.hs
+++ b/test/Database/Fill.hs
@@ -5,7 +5,6 @@ module Database.Fill
 import "uniworx" Import hiding (Option(..), currentYear)
 import Handler.Utils.Form (SheetGrading'(..), SheetType'(..), SheetGroup'(..))
 
-import qualified Data.ByteString as BS
 import qualified Data.ByteString.Lazy as LBS
 import qualified Data.Text as Text
 -- import Data.Text.IO (hPutStrLn)
@@ -30,6 +29,8 @@ import qualified Data.Csv as Csv
 import Crypto.Random (getRandomBytes)
 import Data.List (genericLength)
 
+import qualified Data.Conduit.Combinators as C
+
 
 testdataDir :: FilePath
 testdataDir = "testdata"
@@ -37,7 +38,7 @@ testdataDir = "testdata"
   
 insertFile :: ( HasFileReference fRef, PersistRecordBackend fRef SqlBackend ) => FileReferenceResidual fRef -> FilePath -> DB (Key fRef)
 insertFile residual fileTitle = do
-  fileContent <- liftIO . fmap Just . BS.readFile $ testdataDir </> fileTitle
+  let fileContent = Just . C.sourceFile $ testdataDir </> fileTitle
   fileModified <- liftIO getCurrentTime
   sinkFile' File{..} residual >>= insert