use export db to correctly handle duplicate files

Removed uncorrect UniqueKey key in db schema; a key can appear multiple
times with different files.

The database has to be flushed after each removal. But when adding files
to the export, lots of changes are able to be queued up w/o flushing.
So it's still fairly efficient.

If large removals of files from exports are too slow, an alternative
would be to make two passes over the diff, one pass queueing deletions
from the database, then a flush and the a second pass updating the
location log. But that would use more memory, and need to look up
exportKey twice per removed file, so I've avoided such optimisation yet.

This commit was supported by the NSF-funded DataLad project.

1 files changed, 23 insertions, 18 deletions

diff --git a/Command/Export.hs b/Command/Export.hs
index c09253dc9..3387a14ad 100644
--- a/Command/Export.hs
+++ b/Command/Export.hs
@@ -113,21 +113,20 @@ seek o = do
 startExport :: Remote -> ExportHandle -> Git.LsTree.TreeItem -> CommandStart
 startExport r db ti = do
 	ek <- exportKey (Git.LsTree.sha ti)
-	liftIO $ addExportLocation db (asKey ek) loc
-	stopUnless (notElem (uuid r) <$> loggedLocations (asKey ek)) $ do
+	stopUnless (liftIO $ notElem loc <$> getExportLocation db (asKey ek)) $ do
 		showStart "export" f
-		next $ performExport r ek (Git.LsTree.sha ti) loc
+		next $ performExport r db ek (Git.LsTree.sha ti) loc
   where
 	loc = ExportLocation $ toInternalGitPath f
 	f = getTopFilePath $ Git.LsTree.file ti
 
-performExport :: Remote -> ExportKey -> Sha -> ExportLocation -> CommandPerform
-performExport r ek contentsha loc = do
+performExport :: Remote -> ExportHandle -> ExportKey -> Sha -> ExportLocation -> CommandPerform
+performExport r db ek contentsha loc = do
 	let storer = storeExport $ exportActions r
 	sent <- case ek of
 		AnnexKey k -> ifM (inAnnex k)
 			( metered Nothing k $ \m -> do
-				let rollback = void $ performUnexport r ek loc
+				let rollback = void $ performUnexport r db ek loc
 				sendAnnex k rollback
 					(\f -> storer f k loc m)
 			, do
@@ -142,11 +141,12 @@ performExport r ek contentsha loc = do
 				liftIO $ hClose h
 				storer tmp sha1k loc m
 	if sent
-		then next $ cleanupExport r ek
+		then next $ cleanupExport r db ek loc
 		else stop
 
-cleanupExport :: Remote -> ExportKey -> CommandCleanup
-cleanupExport r ek = do
+cleanupExport :: Remote -> ExportHandle -> ExportKey -> ExportLocation -> CommandCleanup
+cleanupExport r db ek loc = do
+	liftIO $ addExportLocation db (asKey ek) loc
 	logChange (asKey ek) (uuid r) InfoPresent
 	return True
 
@@ -154,23 +154,28 @@ startUnexport :: Remote -> ExportHandle -> Git.DiffTree.DiffTreeItem -> CommandS
 startUnexport r db diff
 	| Git.DiffTree.srcsha diff /= nullSha = do
 		showStart "unexport" f
-		oldk <- exportKey (Git.DiffTree.srcsha diff)
-		liftIO $ removeExportLocation db (asKey oldk) loc
-		next $ performUnexport r oldk loc
+		ek <- exportKey (Git.DiffTree.srcsha diff)
+		next $ performUnexport r db ek loc
 	| otherwise = stop
   where
 	loc = ExportLocation $ toInternalGitPath f
 	f = getTopFilePath $ Git.DiffTree.file diff
 
-performUnexport :: Remote -> ExportKey -> ExportLocation -> CommandPerform
-performUnexport r ek loc = do
+performUnexport :: Remote -> ExportHandle -> ExportKey -> ExportLocation -> CommandPerform
+performUnexport r db ek loc = do
 	let remover = removeExport $ exportActions r
 	ok <- remover (asKey ek) loc
 	if ok
-		then next $ cleanupUnexport r ek
+		then next $ cleanupUnexport r db ek loc
 		else stop
 
-cleanupUnexport :: Remote -> ExportKey -> CommandCleanup
-cleanupUnexport r ek = do
-	logChange (asKey ek) (uuid r) InfoMissing
+cleanupUnexport :: Remote -> ExportHandle -> ExportKey -> ExportLocation -> CommandCleanup
+cleanupUnexport r db ek loc = do
+	liftIO $ do
+		removeExportLocation db (asKey ek) loc
+		-- Flush so that getExportLocation sees this and any
+		-- other removals of the key.
+		flushDbQueue db
+	whenM (liftIO $ null <$> getExportLocation db (asKey ek)) $
+		logChange (asKey ek) (uuid r) InfoMissing
 	return True