Skip resolving paths for symlinks during index if the path isn't a symlink.

godirwalk can inform us if the file currently processed is a symlink or not (which is gathered without extra stat syscalls).Using this information to skip resolving the symlink to the absolute path (which is necessary to get the stat info of the image file instead of the symlink to it) saves on a lot of syscalls. Resolve causes a Stat syscall for each level in the path, which is very expensive and slows down scanning.

internal/photoprism/index.go

@@ -187,7 +187,15 @@ func (ind *Index) Start(o IndexOptions) fs.Done {
 				return nil
 			}
 
-			mf, err := NewMediaFile(fileName)
+			var mf *MediaFile
+			var err error
+			if isSymlink {
+				mf, err = NewMediaFile(fileName)
+			} else {
+				// If the file found while scanning is not a symlink we can
+				// skip resolving the fileName, which is resource intensive.
+				mf, err = NewMediaFileSkipResolve(fileName, fileName)
+			}
 
 			// Check if file exists and is not empty.
 			if err != nil {

internal/photoprism/mediafile.go

@@ -36,39 +36,53 @@ import (
 
 // MediaFile represents a single photo, video or sidecar file.
 type MediaFile struct {
-	fileName       string
-	fileRoot       string
-	statErr        error
-	modTime        time.Time
-	fileSize       int64
-	fileType       fs.Type
-	mimeType       string
-	takenAt        time.Time
-	takenAtSrc     string
-	hash           string
-	checksum       string
-	hasJpeg        bool
-	noColorProfile bool
-	colorProfile   string
-	width          int
-	height         int
-	metaData       meta.Data
-	metaOnce       sync.Once
-	fileMutex      sync.Mutex
-	location       *entity.Cell
-	imageConfig    *image.Config
+	fileName         string
+	fileNameResolved string
+	fileRoot         string
+	statErr          error
+	modTime          time.Time
+	fileSize         int64
+	fileType         fs.Type
+	mimeType         string
+	takenAt          time.Time
+	takenAtSrc       string
+	hash             string
+	checksum         string
+	hasJpeg          bool
+	noColorProfile   bool
+	colorProfile     string
+	width            int
+	height           int
+	metaData         meta.Data
+	metaOnce         sync.Once
+	fileMutex        sync.Mutex
+	location         *entity.Cell
+	imageConfig      *image.Config
 }
 
 // NewMediaFile returns a new media file.
 func NewMediaFile(fileName string) (m *MediaFile, err error) {
+	fileNameResolved, err := fs.Resolve(fileName)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewMediaFileSkipResolve(fileName, fileNameResolved)
+}
+
+// NewMediaFileSkipResolve returns a new media file without resolving symlinks.
+// This is useful because if it's known fileName is fully resolved it's a lot
+// faster.
+func NewMediaFileSkipResolve(fileName string, fileNameResolved string) (m *MediaFile, err error) {
 	// Create struct.
 	m = &MediaFile{
-		fileName: fileName,
-		fileRoot: entity.RootUnknown,
-		fileType: fs.UnknownType,
-		metaData: meta.New(),
-		width:    -1,
-		height:   -1,
+		fileName:         fileName,
+		fileNameResolved: fileNameResolved,
+		fileRoot:         entity.RootUnknown,
+		fileType:         fs.UnknownType,
+		metaData:         meta.New(),
+		width:            -1,
+		height:           -1,
 	}
 
 	// Check if file exists and is not empty.
@@ -97,14 +111,7 @@ func (m *MediaFile) Stat() (size int64, mod time.Time, err error) {
 		return m.fileSize, m.modTime, m.statErr
 	}
 
-	fileName := m.FileName()
-
-	// Resolve symlinks.
-	if fileName, err = fs.Resolve(fileName); err != nil {
-		m.statErr = err
-		m.modTime = time.Time{}
-		m.fileSize = -1
-	} else if s, err := os.Stat(fileName); err != nil {
+	if s, err := os.Stat(m.fileNameResolved); err != nil {
 		m.statErr = err
 		m.modTime = time.Time{}
 		m.fileSize = -1