speed up very first tree import by 25%

Reading from the cidsdb is responsible for about 25% of the runtime of
an import. Since the cidmap is used to store the same information in
ram, the cidsdb is not written to during an import any longer. And so,
if it started off empty (and updateFromLog wasn't needed), those reads
can just be skipped.

This is kind of a cheesy optimisation, since after any import from any
special remote, the database will no longer be empty, so it's a single
use optimisation. But it's probably not uncommon to start by importing a
lot of files, and it can save a lot of time then.

Sponsored-by: Brock Spratlen on Patreon

Annex/Import.hs

@@ -626,9 +626,9 @@ importKeys remote importtreeconfig importcontent thirdpartypopulated importablec
 	-- avoid two threads both importing the same content identifier.
 	importing <- liftIO $ newTVarIO S.empty
 	withciddb $ \db -> do
-		CIDDb.needsUpdateFromLog db
-			>>= maybe noop (CIDDb.updateFromLog db)
-		(prepclock (run cidmap importing db))
+		db' <- CIDDb.needsUpdateFromLog db
+			>>= maybe (pure db) (CIDDb.updateFromLog db)
+		(prepclock (run cidmap importing db'))
   where
 	-- When not importing content, reuse the same vector
 	-- clock for all state that's recorded. This can save
@@ -925,10 +925,16 @@ importKeys remote importtreeconfig importcontent thirdpartypopulated importablec
 				getTopFilePath subdir P.</> fromImportLocation loc
 
 	getcidkey cidmap db cid = liftIO $
-		CIDDb.getContentIdentifierKeys db rs cid >>= \case
-			[] -> atomically $
-				maybeToList . M.lookup cid <$> readTVar cidmap
-			l -> return l
+		-- Avoiding querying the database when it's empty speeds up
+		-- the initial import.
+		if CIDDb.databaseIsEmpty db
+			then getcidkeymap cidmap cid
+			else CIDDb.getContentIdentifierKeys db rs cid >>= \case
+				[] -> getcidkeymap cidmap cid
+				l -> return l
+
+	getcidkeymap cidmap cid =
+		atomically $ maybeToList . M.lookup cid <$> readTVar cidmap
 
 	recordcidkey cidmap cid k = do
 		liftIO $ atomically $ modifyTVar' cidmap $

CHANGELOG

@@ -77,8 +77,7 @@ git-annex (10.20230408) UNRELEASED; urgency=medium
   * repair: Fix handling of git ref names on Windows.
   * Large speed up to importing trees from special remotes that contain a lot
     of files, by only processing changed files.
-  * Speed up importing trees from special remotes somewhat by avoiding
-    redundant writes to sqlite database.
+  * Some other speedups to importing trees from special remotes.
 
  -- Joey Hess <id@joeyh.name>  Sat, 08 Apr 2023 13:57:18 -0400
 

Database/ContentIdentifier.hs

@@ -1,6 +1,6 @@
 {- Sqlite database of ContentIdentifiers imported from special remotes.
  -
- - Copyright 2019 Joey Hess <id@joeyh.name>
+ - Copyright 2019-2023 Joey Hess <id@joeyh.name>
  -:
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -19,6 +19,7 @@
 
 module Database.ContentIdentifier (
 	ContentIdentifierHandle,
+	databaseIsEmpty,
 	openDb,
 	closeDb,
 	flushDbQueue,
@@ -57,7 +58,10 @@ import Database.Persist.Sqlite (runSqlite)
 import qualified System.FilePath.ByteString as P
 import qualified Data.Text as T
 
-data ContentIdentifierHandle = ContentIdentifierHandle H.DbQueue
+data ContentIdentifierHandle = ContentIdentifierHandle H.DbQueue Bool
+
+databaseIsEmpty :: ContentIdentifierHandle -> Bool
+databaseIsEmpty (ContentIdentifierHandle _ b) = b
 
 share [mkPersist sqlSettings, mkMigrate "migrateContentIdentifier"] [persistLowerCase|
 ContentIdentifiers
@@ -81,23 +85,23 @@ openDb :: Annex ContentIdentifierHandle
 openDb = do
 	dbdir <- calcRepo' gitAnnexContentIdentifierDbDir
 	let db = dbdir P.</> "db"
-	ifM (liftIO $ not <$> R.doesPathExist db)
-		( initDb db $ void $ 
+	isnew <- liftIO $ not <$> R.doesPathExist db
+	if isnew
+		then initDb db $ void $ 
 			runMigrationSilent migrateContentIdentifier
 		-- Migrate from old version of database, which had
 		-- an incorrect uniqueness constraint on the
 		-- ContentIdentifiers table.
-		, liftIO $ runSqlite (T.pack (fromRawFilePath db)) $ void $
+		else liftIO $ runSqlite (T.pack (fromRawFilePath db)) $ void $
 			runMigrationSilent migrateContentIdentifier
-		)
 	h <- liftIO $ H.openDbQueue db "content_identifiers"
-	return $ ContentIdentifierHandle h
+	return $ ContentIdentifierHandle h isnew
 
 closeDb :: ContentIdentifierHandle -> Annex ()
-closeDb (ContentIdentifierHandle h) = liftIO $ H.closeDbQueue h
+closeDb (ContentIdentifierHandle h _) = liftIO $ H.closeDbQueue h
 
 queueDb :: ContentIdentifierHandle -> SqlPersistM () -> IO ()
-queueDb (ContentIdentifierHandle h) = H.queueDb h checkcommit
+queueDb (ContentIdentifierHandle h _) = H.queueDb h checkcommit
   where
 	-- commit queue after 1000 changes
 	checkcommit sz _lastcommittime
@@ -105,7 +109,7 @@ queueDb (ContentIdentifierHandle h) = H.queueDb h checkcommit
 		| otherwise = return False
 
 flushDbQueue :: ContentIdentifierHandle -> IO ()
-flushDbQueue (ContentIdentifierHandle h) = H.flushDbQueue h
+flushDbQueue (ContentIdentifierHandle h _) = H.flushDbQueue h
 
 -- Be sure to also update the git-annex branch when using this.
 recordContentIdentifier :: ContentIdentifierHandle -> RemoteStateHandle -> ContentIdentifier -> Key -> IO ()
@@ -113,7 +117,7 @@ recordContentIdentifier h (RemoteStateHandle u) cid k = queueDb h $ do
 	void $ insertUniqueFast $ ContentIdentifiers u cid k
 
 getContentIdentifiers :: ContentIdentifierHandle -> RemoteStateHandle -> Key -> IO [ContentIdentifier]
-getContentIdentifiers (ContentIdentifierHandle h) (RemoteStateHandle u) k = 
+getContentIdentifiers (ContentIdentifierHandle h _) (RemoteStateHandle u) k = 
 	H.queryDbQueue h $ do
 		l <- selectList
 			[ ContentIdentifiersKey ==. k
@@ -122,7 +126,7 @@ getContentIdentifiers (ContentIdentifierHandle h) (RemoteStateHandle u) k =
 		return $ map (contentIdentifiersCid . entityVal) l
 
 getContentIdentifierKeys :: ContentIdentifierHandle -> RemoteStateHandle -> ContentIdentifier -> IO [Key]
-getContentIdentifierKeys (ContentIdentifierHandle h) (RemoteStateHandle u) cid = 
+getContentIdentifierKeys (ContentIdentifierHandle h _) (RemoteStateHandle u) cid = 
 	H.queryDbQueue h $ do
 		l <- selectList
 			[ ContentIdentifiersCid ==. cid
@@ -136,7 +140,7 @@ recordAnnexBranchTree h s = queueDb h $ do
 	void $ insertUniqueFast $ AnnexBranch $ toSSha s
 
 getAnnexBranchTree :: ContentIdentifierHandle -> IO Sha
-getAnnexBranchTree (ContentIdentifierHandle h) = H.queryDbQueue h $ do
+getAnnexBranchTree (ContentIdentifierHandle h _) = H.queryDbQueue h $ do
 	l <- selectList ([] :: [Filter AnnexBranch]) []
 	case l of
 		(s:[]) -> return $ fromSSha $ annexBranchTree $ entityVal s
@@ -153,8 +157,8 @@ needsUpdateFromLog db = do
 		_ -> return Nothing
 
 {- The database should be locked for write when calling this. -}
-updateFromLog :: ContentIdentifierHandle -> (Sha, Sha) -> Annex ()
-updateFromLog db (oldtree, currtree) = do
+updateFromLog :: ContentIdentifierHandle -> (Sha, Sha) -> Annex ContentIdentifierHandle
+updateFromLog db@(ContentIdentifierHandle h _) (oldtree, currtree) = do
 	(l, cleanup) <- inRepo $
 		DiffTree.diffTreeRecursive oldtree currtree
 	mapM_ go l
@@ -162,6 +166,7 @@ updateFromLog db (oldtree, currtree) = do
 	liftIO $ do
 		recordAnnexBranchTree db currtree
 		flushDbQueue db
+	return (ContentIdentifierHandle h False)
   where
 	go ti = case extLogFileKey remoteContentIdentifierExt (getTopFilePath (DiffTree.file ti)) of
 		Nothing -> return ()

Remote/Helper/ExportImport.hs

@@ -280,14 +280,14 @@ adjustExportImport' isexport isimport r rs = do
 			Nothing -> ifM (liftIO $ atomically $ tryPutTMVar lcklckv ())
 				( do
 					db <- ContentIdentifier.openDb
-					ContentIdentifier.needsUpdateFromLog db >>= \case
+					db' <- ContentIdentifier.needsUpdateFromLog db >>= \case
 						Just v -> do
 							cidlck <- calcRepo' gitAnnexContentIdentifierLock 
 							withExclusiveLock cidlck $
 								ContentIdentifier.updateFromLog db v
-						Nothing -> noop
-					liftIO $ atomically $ putTMVar dbtv db
-					return db
+						Nothing -> pure db
+					liftIO $ atomically $ putTMVar dbtv db'
+					return db'
 				-- loser waits for winner to open the db and
 				-- can then also use its handle
 				, liftIO $ atomically (readTMVar dbtv)