cache: Remove entries that no longer exist in the source

list directory with 25k files

before(1.43.1)
5m24s

after
3m21s

backend/cache/cache.go

@@ -11,6 +11,7 @@ import (
 	"os/signal"
 	"path"
 	"path/filepath"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -891,7 +892,6 @@ func (f *Fs) List(dir string) (entries fs.DirEntries, err error) {
 		fs.Debugf(dir, "list: cached entries: %v", entries)
 		return entries, nil
 	}
-	// FIXME need to clean existing cached listing
 
 	// we first search any temporary files stored locally
 	var cachedEntries fs.DirEntries
@@ -917,27 +917,42 @@ func (f *Fs) List(dir string) (entries fs.DirEntries, err error) {
 	}
 
 	// search from the source
-	entries, err = f.Fs.List(dir)
+	sourceEntries, err := f.Fs.List(dir)
 	if err != nil {
 		return nil, err
 	}
-	fs.Debugf(dir, "list: read %v from source", len(entries))
+	fs.Debugf(dir, "list: read %v from source", len(sourceEntries))
-	fs.Debugf(dir, "list: source entries: %v", entries)
+	fs.Debugf(dir, "list: source entries: %v", sourceEntries)
+
+	sort.Sort(sourceEntries)
+	for _, entry := range entries {
+		entryRemote := entry.Remote()
+		i := sort.Search(len(sourceEntries), func(i int) bool { return sourceEntries[i].Remote() >= entryRemote })
+		if i < len(sourceEntries) && sourceEntries[i].Remote() == entryRemote {
+			continue
+		}
+		fp := path.Join(f.Root(), entryRemote)
+		switch entry.(type) {
+		case fs.Object:
+			_ = f.cache.RemoveObject(fp)
+		case fs.Directory:
+			_ = f.cache.RemoveDir(fp)
+		}
+		fs.Debugf(dir, "list: remove entry: %v", entryRemote)
+	}
+	entries = nil
 
 	// and then iterate over the ones from source (temp Objects will override source ones)
 	var batchDirectories []*Directory
-	for _, entry := range entries {
+	sort.Sort(cachedEntries)
+	tmpCnt := len(cachedEntries)
+	for _, entry := range sourceEntries {
 		switch o := entry.(type) {
 		case fs.Object:
 			// skip over temporary objects (might be uploading)
-			found := false
+			oRemote := o.Remote()
-			for _, t := range cachedEntries {
+			i := sort.Search(tmpCnt, func(i int) bool { return cachedEntries[i].Remote() >= oRemote })
-				if t.Remote() == o.Remote() {
+			if i < tmpCnt && cachedEntries[i].Remote() == oRemote {
-					found = true
-					break
-				}
-			}
-			if found {
 				continue
 			}
 			co := ObjectFromOriginal(f, o).persist()