Sped up view branch construction by 50%

A benchmark in my sound repository with `git-annex view feedtitle=*`
took 2:52 wall clock time before and 1:58 after. Though it still only used
130% of CPU.

This is the same kind of optimisation that is in seekFilteredKeys, though
that precaches location logs while this streams the metadata logs direct
to parsing them.

seekFilteredKeys contains more streaming, to find the annexed files, and
this could be further sped up with similar streaming.

Sponsored-by: Nicholas Golder-Manning on Patreon

Annex/View.hs

@@ -15,12 +15,14 @@ import Types.View
 import Types.MetaData
 import Annex.MetaData
 import qualified Annex
+import qualified Annex.Branch
 import qualified Git
 import qualified Git.DiffTree as DiffTree
 import qualified Git.Branch
 import qualified Git.LsFiles
 import qualified Git.LsTree
 import qualified Git.Ref
+import Git.CatFile
 import Git.UpdateIndex
 import Git.Sha
 import Git.Types
@@ -29,6 +31,8 @@ import Annex.WorkTree
 import Annex.GitOverlay
 import Annex.Link
 import Annex.CatFile
+import Annex.Concurrent
+import Logs
 import Logs.MetaData
 import Logs.View
 import Utility.Glob
@@ -41,6 +45,7 @@ import qualified Data.ByteString as B
 import qualified Data.Set as S
 import qualified Data.Map as M
 import qualified System.FilePath.ByteString as P
+import Control.Concurrent.Async
 import "mtl" Control.Monad.Writer
 
 {- Each visible ViewFilter in a view results in another level of
@@ -435,9 +440,10 @@ applyView' mkviewedfile getfilemetadata view = do
 	top <- fromRepo Git.repoPath
 	(l, clean) <- inRepo $ Git.LsFiles.inRepoDetails [] [top]
 	applyView'' mkviewedfile getfilemetadata view l clean $ 
-		\go (f, sha, mode) -> do
+		\(f, sha, mode) -> do
 			topf <- inRepo (toTopFilePath f)
-			go topf sha (toTreeItemType mode) =<< lookupKey f
+			k <- lookupKey f
+			return (topf, sha, toTreeItemType mode, k)
 	genViewBranch view
 
 applyView''
@@ -446,29 +452,58 @@ applyView''
 	-> View
 	-> [t]
 	-> IO Bool
-	-> ((TopFilePath -> Sha -> Maybe TreeItemType -> Maybe Key -> Annex ()) -> t -> Annex ())
+	-> (t -> Annex (TopFilePath, Sha, Maybe TreeItemType, Maybe Key))
 	-> Annex ()
-applyView'' mkviewedfile getfilemetadata view l clean a = do
+applyView'' mkviewedfile getfilemetadata view l clean conv = do
 	viewg <- withNewViewIndex gitRepo
 	withUpdateIndex viewg $ \uh -> do
-		forM_ l $ a (go uh)
-		liftIO $ void clean
+		g <- Annex.gitRepo
+		gc <- Annex.getGitConfig
+		-- Streaming the metadata like this is an optimisation.
+		catObjectStream g $ \mdfeeder mdcloser mdreader -> do
+			tid <- liftIO . async =<< forkState
+				(getmetadata gc mdfeeder mdcloser l)
+			process uh mdreader
+			join (liftIO (wait tid))
+			liftIO $ void clean
   where
 	genviewedfiles = viewedFiles view mkviewedfile -- enables memoization
 
-	go uh topf _sha _mode (Just k) = do
-		metadata <- getCurrentMetaData k
-		let f = fromRawFilePath $ getTopFilePath topf
-		let metadata' = getfilemetadata f `unionMetaData` metadata
-		forM_ (genviewedfiles f metadata') $ \fv -> do
-			f' <- fromRepo (fromTopFilePath $ asTopFilePath $ toRawFilePath fv)
-			stagesymlink uh f' =<< calcRepo (gitAnnexLink f' k)
-	go uh topf sha (Just treeitemtype) Nothing
-		| "." `B.isPrefixOf` getTopFilePath topf =
+	getmetadata _ _ mdcloser [] = liftIO mdcloser
+	getmetadata gc mdfeeder mdcloser (t:ts) = do
+		v@(topf, _sha, _treeitemtype, mkey) <- conv t
+		let feed mdlogf = liftIO $ mdfeeder
+			(v, Git.Ref.branchFileRef Annex.Branch.fullname mdlogf)
+		case mkey of
+			Just key -> feed (metaDataLogFile gc key)
+			Nothing
+				-- Handle toplevel dotfiles that are not
+				-- annexed files by feeding through a query
+				-- for dummy metadata. Calling
+				-- Git.UpdateIndex.streamUpdateIndex'
+				-- here would race with process's calls
+				-- to it.
+				| "." `B.isPrefixOf` getTopFilePath topf ->
+					feed "dummy"
+				| otherwise -> noop
+		getmetadata gc mdfeeder mdcloser ts
+
+	process uh mdreader = liftIO mdreader >>= \case
+		Just ((topf, _, _, Just k), Just mdlog) -> do
+			let metadata = parseCurrentMetaData mdlog
+			let f = fromRawFilePath $ getTopFilePath topf
+			let metadata' = getfilemetadata f `unionMetaData` metadata
+			forM_ (genviewedfiles f metadata') $ \fv -> do
+				f' <- fromRepo (fromTopFilePath $ asTopFilePath $ toRawFilePath fv)
+				stagesymlink uh f' =<< calcRepo (gitAnnexLink f' k)
+			process uh mdreader
+		Just ((topf, sha, Just treeitemtype, Nothing), _) -> do
 			liftIO $ Git.UpdateIndex.streamUpdateIndex' uh $
 				pureStreamer $ updateIndexLine sha treeitemtype topf
-	go _ _ _ _  _ = noop
-
+			process uh mdreader
+		Just _ -> process uh mdreader
+		Nothing -> return ()
+	
 	stagesymlink uh f linktarget = do
 		sha <- hashSymlink linktarget
 		liftIO . Git.UpdateIndex.streamUpdateIndex' uh
@@ -490,17 +525,18 @@ updateView view = do
 		(Git.LsTree.LsTreeLong True)
 		(viewParentBranch view)
 	applyView'' viewedFileFromReference getWorkTreeMetaData view l clean $
-		\go ti -> do
+		\ti -> do
 			let ref = Git.Ref.branchFileRef (viewParentBranch view)
 				(getTopFilePath (Git.LsTree.file ti))
 			k <- case Git.LsTree.size ti of
 				Nothing -> catKey ref
 				Just sz -> catKey' ref sz
-			go
-				(Git.LsTree.file ti)
-				(Git.LsTree.sha ti)
-				(toTreeItemType (Git.LsTree.mode ti))
-				k
+			return
+				( (Git.LsTree.file ti)
+				, (Git.LsTree.sha ti)
+				, (toTreeItemType (Git.LsTree.mode ti))
+				, k
+				)
 	oldcommit <- inRepo $ Git.Ref.sha (branchView view)
 	oldtree <- maybe (pure Nothing) (inRepo . Git.Ref.tree) oldcommit
 	newtree <- withViewIndex $ inRepo Git.Branch.writeTree

CHANGELOG

@@ -20,6 +20,7 @@ git-annex (10.20230127) UNRELEASED; urgency=medium
     number, the same as git does.
   * sync: Warn when the adjusted basis ref cannot be found, as happens eg when
     the user has renamed branches.
+  * Sped up view branch construction by 50%.
 
  -- Joey Hess <id@joeyh.name>  Mon, 06 Feb 2023 13:39:18 -0400
 

doc/todo/faster_incremental_update_of_view_branch_by_git-annex_sync.mdwn

@@ -18,3 +18,6 @@ It may also be that just improving the precaching of metadata logs
 would improve the speed a lot. The streaming precaching of location logs
 sped up some commands around 2x before IIRC.
 
+> catObjectStream of metadata logs sped view constriction up by ~50%.
+> More streaming should speed it up more; it still uses
+> lookupKey/catKey once per file. --[[Joey]]