repository/master_index: Optimize Index.Lookup()

When looking up a blob in the master index, with several
indexes present in the master index, a significant amount of time
is spent generating errors for each failed lookup.  However, these
errors are often used to check if a blob is present, but the contents
are not inspected making the overhead of the error not useful.

Instead, change Index.Lookup (and Index.LookupSize) to instead return
a boolean denoting if the blob was found instead of an error.  Also change
all the calls to these functions to handle the new function signature.

benchmark                                            old ns/op     new ns/op     delta
BenchmarkMasterIndexLookupSingleIndex-6              820           897           +9.39%
BenchmarkMasterIndexLookupMultipleIndex-6            12821         2001          -84.39%
BenchmarkMasterIndexLookupSingleIndexUnknown-6       5378          492           -90.85%
BenchmarkMasterIndexLookupMultipleIndexUnknown-6     17026         1649          -90.31%

benchmark                                            old allocs     new allocs     delta
BenchmarkMasterIndexLookupSingleIndex-6              9              9              +0.00%
BenchmarkMasterIndexLookupMultipleIndex-6            59             19             -67.80%
BenchmarkMasterIndexLookupSingleIndexUnknown-6       22             6              -72.73%
BenchmarkMasterIndexLookupMultipleIndexUnknown-6     72             16             -77.78%

benchmark                                            old bytes     new bytes     delta
BenchmarkMasterIndexLookupSingleIndex-6              160           160           +0.00%
BenchmarkMasterIndexLookupMultipleIndex-6            3200          240           -92.50%
BenchmarkMasterIndexLookupSingleIndexUnknown-6       1232          48            -96.10%
BenchmarkMasterIndexLookupMultipleIndexUnknown-6     4272          128           -97.00%

cmd/restic/cmd_cat.go

@@ -165,8 +165,8 @@ func runCat(gopts GlobalOptions, args []string) error {
 
 	case "blob":
 		for _, t := range []restic.BlobType{restic.DataBlob, restic.TreeBlob} {
-			list, err := repo.Index().Lookup(id, t)
+			list, found := repo.Index().Lookup(id, t)
-			if err != nil {
+			if !found {
 				continue
 			}
 			blob := list[0]

cmd/restic/cmd_diff.go

@@ -135,9 +135,9 @@ func updateBlobs(repo restic.Repository, blobs restic.BlobSet, stats *DiffStat)
 			stats.TreeBlobs++
 		}
 
-		size, err := repo.LookupBlobSize(h.ID, h.Type)
+		size, found := repo.LookupBlobSize(h.ID, h.Type)
-		if err != nil {
+		if !found {
-			Warnf("unable to find blob size for %v: %v\n", h, err)
+			Warnf("unable to find blob size for %v\n", h)
 			continue
 		}
 

cmd/restic/cmd_dump.go

@@ -59,9 +59,9 @@ func splitPath(path string) []string {
 func dumpNode(ctx context.Context, repo restic.Repository, node *restic.Node) error {
 	var buf []byte
 	for _, id := range node.Content {
-		size, err := repo.LookupBlobSize(id, restic.DataBlob)
+		size, found := repo.LookupBlobSize(id, restic.DataBlob)
-		if err != nil {
+		if !found {
-			return err
+			return errors.Errorf("id %v not found in repository", id)
 		}
 
 		buf = buf[:cap(buf)]

internal/archiver/archive_reader_test.go

@@ -43,9 +43,9 @@ func checkSavedFile(t *testing.T, repo restic.Repository, treeID restic.ID, name
 
 	// check blobs
 	for i, id := range node.Content {
-		size, err := repo.LookupBlobSize(id, restic.DataBlob)
+		size, found := repo.LookupBlobSize(id, restic.DataBlob)
-		if err != nil {
+		if !found {
-			t.Fatal(err)
+			t.Fatal("Failed to find blob", id.Str())
 		}
 
 		buf := restic.NewBlobBuffer(int(size))
@@ -55,7 +55,7 @@ func checkSavedFile(t *testing.T, repo restic.Repository, treeID restic.ID, name
 		}
 
 		buf2 := make([]byte, int(size))
-		_, err = io.ReadFull(rd, buf2)
+		_, err := io.ReadFull(rd, buf2)
 		if err != nil {
 			t.Fatal(err)
 		}

internal/archiver/archiver.go

@@ -86,8 +86,8 @@ func (arch *Archiver) isKnownBlob(id restic.ID, t restic.BlobType) bool {
 
 	arch.knownBlobs.Insert(id)
 
-	_, err := arch.repo.Index().Lookup(id, t)
+	_, found := arch.repo.Index().Lookup(id, t)
-	if err == nil {
+	if found {
 		return true
 	}
 

internal/fuse/file.go

@@ -4,6 +4,7 @@
 package fuse
 
 import (
+	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/restic"
 
 	"github.com/restic/restic/internal/debug"
@@ -36,9 +37,10 @@ func newFile(ctx context.Context, root *Root, inode uint64, node *restic.Node) (
 	for i, id := range node.Content {
 		size, ok := root.blobSizeCache.Lookup(id)
 		if !ok {
-			size, err = root.repo.LookupBlobSize(id, restic.DataBlob)
+			var found bool
-			if err != nil {
+			size, found = root.repo.LookupBlobSize(id, restic.DataBlob)
-				return nil, err
+			if !found {
+				return nil, errors.Errorf("id %v not found in repository", id)
 			}
 		}
 

internal/fuse/file_test.go

@@ -81,8 +81,8 @@ func TestFuseFile(t *testing.T) {
 		memfile  []byte
 	)
 	for _, id := range content {
-		size, err := repo.LookupBlobSize(id, restic.DataBlob)
+		size, found := repo.LookupBlobSize(id, restic.DataBlob)
-		rtest.OK(t, err)
+		rtest.Assert(t, found, "Expected to find blob id %v", id)
 		filesize += uint64(size)
 
 		buf := restic.NewBlobBuffer(int(size))

internal/repository/index.go

@@ -110,7 +110,7 @@ func (idx *Index) Store(blob restic.PackedBlob) {
 }
 
 // Lookup queries the index for the blob ID and returns a restic.PackedBlob.
-func (idx *Index) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.PackedBlob, err error) {
+func (idx *Index) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.PackedBlob, found bool) {
 	idx.m.Lock()
 	defer idx.m.Unlock()
 
@@ -136,11 +136,11 @@ func (idx *Index) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.Pack
 			blobs = append(blobs, blob)
 		}
 
-		return blobs, nil
+		return blobs, true
 	}
 
 	debug.Log("id %v not found", id.Str())
-	return nil, errors.Errorf("id %v not found in index", id)
+	return nil, false
 }
 
 // ListPack returns a list of blobs contained in a pack.
@@ -180,13 +180,13 @@ func (idx *Index) Has(id restic.ID, tpe restic.BlobType) bool {
 
 // LookupSize returns the length of the plaintext content of the blob with the
 // given id.
-func (idx *Index) LookupSize(id restic.ID, tpe restic.BlobType) (plaintextLength uint, err error) {
+func (idx *Index) LookupSize(id restic.ID, tpe restic.BlobType) (plaintextLength uint, found bool) {
-	blobs, err := idx.Lookup(id, tpe)
+	blobs, found := idx.Lookup(id, tpe)
-	if err != nil {
+	if !found {
-		return 0, err
+		return 0, found
 	}
 
-	return uint(restic.PlaintextLength(int(blobs[0].Length))), nil
+	return uint(restic.PlaintextLength(int(blobs[0].Length))), true
 }
 
 // Supersedes returns the list of indexes this index supersedes, if any.

internal/repository/index_test.go

@@ -65,8 +65,8 @@ func TestIndexSerialize(t *testing.T) {
 	rtest.OK(t, err)
 
 	for _, testBlob := range tests {
-		list, err := idx.Lookup(testBlob.id, testBlob.tpe)
+		list, found := idx.Lookup(testBlob.id, testBlob.tpe)
-		rtest.OK(t, err)
+		rtest.Assert(t, found, "Expected to find blob id %v", testBlob.id.Str())
 
 		if len(list) != 1 {
 			t.Errorf("expected one result for blob %v, got %v: %v", testBlob.id.Str(), len(list), list)
@@ -78,8 +78,8 @@ func TestIndexSerialize(t *testing.T) {
 		rtest.Equals(t, testBlob.offset, result.Offset)
 		rtest.Equals(t, testBlob.length, result.Length)
 
-		list2, err := idx2.Lookup(testBlob.id, testBlob.tpe)
+		list2, found := idx2.Lookup(testBlob.id, testBlob.tpe)
-		rtest.OK(t, err)
+		rtest.Assert(t, found, "Expected to find blob id %v", testBlob.id)
 
 		if len(list2) != 1 {
 			t.Errorf("expected one result for blob %v, got %v: %v", testBlob.id.Str(), len(list2), list2)
@@ -146,8 +146,8 @@ func TestIndexSerialize(t *testing.T) {
 
 	// all new blobs must be in the index
 	for _, testBlob := range newtests {
-		list, err := idx3.Lookup(testBlob.id, testBlob.tpe)
+		list, found := idx3.Lookup(testBlob.id, testBlob.tpe)
-		rtest.OK(t, err)
+		rtest.Assert(t, found, "Expected to find blob id %v", testBlob.id.Str())
 
 		if len(list) != 1 {
 			t.Errorf("expected one result for blob %v, got %v: %v", testBlob.id.Str(), len(list), list)
@@ -293,8 +293,8 @@ func TestIndexUnserialize(t *testing.T) {
 	rtest.OK(t, err)
 
 	for _, test := range exampleTests {
-		list, err := idx.Lookup(test.id, test.tpe)
+		list, found := idx.Lookup(test.id, test.tpe)
-		rtest.OK(t, err)
+		rtest.Assert(t, found, "Expected to find blob id %v", test.id.Str())
 
 		if len(list) != 1 {
 			t.Errorf("expected one result for blob %v, got %v: %v", test.id.Str(), len(list), list)
@@ -341,8 +341,8 @@ func TestIndexUnserializeOld(t *testing.T) {
 	rtest.OK(t, err)
 
 	for _, test := range exampleTests {
-		list, err := idx.Lookup(test.id, test.tpe)
+		list, found := idx.Lookup(test.id, test.tpe)
-		rtest.OK(t, err)
+		rtest.Assert(t, found, "Expected to find blob id %v", test.id.Str())
 
 		if len(list) != 1 {
 			t.Errorf("expected one result for blob %v, got %v: %v", test.id.Str(), len(list), list)

internal/repository/master_index.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"sync"
 
-	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/restic"
 
 	"github.com/restic/restic/internal/debug"
@@ -22,36 +21,36 @@ func NewMasterIndex() *MasterIndex {
 }
 
 // Lookup queries all known Indexes for the ID and returns the first match.
-func (mi *MasterIndex) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.PackedBlob, err error) {
+func (mi *MasterIndex) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.PackedBlob, found bool) {
 	mi.idxMutex.RLock()
 	defer mi.idxMutex.RUnlock()
 
 	debug.Log("looking up id %v, tpe %v", id.Str(), tpe)
 
 	for _, idx := range mi.idx {
-		blobs, err = idx.Lookup(id, tpe)
+		blobs, found = idx.Lookup(id, tpe)
-		if err == nil {
+		if found {
 			debug.Log("found id %v: %v", id.Str(), blobs)
 			return
 		}
 	}
 
 	debug.Log("id %v not found in any index", id.Str())
-	return nil, errors.Errorf("id %v not found in any index", id)
+	return nil, false
 }
 
 // LookupSize queries all known Indexes for the ID and returns the first match.
-func (mi *MasterIndex) LookupSize(id restic.ID, tpe restic.BlobType) (uint, error) {
+func (mi *MasterIndex) LookupSize(id restic.ID, tpe restic.BlobType) (uint, bool) {
 	mi.idxMutex.RLock()
 	defer mi.idxMutex.RUnlock()
 
 	for _, idx := range mi.idx {
-		if idx.Has(id, tpe) {
+		if size, found := idx.LookupSize(id, tpe); found {
-			return idx.LookupSize(id, tpe)
+			return size, found
 		}
 	}
 
-	return 0, errors.Errorf("id %v not found in any index", id)
+	return 0, false
 }
 
 // ListPack returns the list of blobs in a pack. The first matching index is

internal/repository/master_index_test.go

@@ -0,0 +1,123 @@
+package repository_test
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/restic/restic/internal/repository"
+	"github.com/restic/restic/internal/restic"
+	rtest "github.com/restic/restic/internal/test"
+)
+
+func TestMasterIndexLookup(t *testing.T) {
+	idInIdx1 := restic.NewRandomID()
+	idInIdx2 := restic.NewRandomID()
+
+	blob1 := restic.PackedBlob{
+		PackID: restic.NewRandomID(),
+		Blob: restic.Blob{
+			Type:   restic.DataBlob,
+			ID:     idInIdx1,
+			Length: 10,
+			Offset: 0,
+		},
+	}
+
+	blob2 := restic.PackedBlob{
+		PackID: restic.NewRandomID(),
+		Blob: restic.Blob{
+			Type:   restic.DataBlob,
+			ID:     idInIdx2,
+			Length: 100,
+			Offset: 10,
+		},
+	}
+
+	idx1 := repository.NewIndex()
+	idx1.Store(blob1)
+
+	idx2 := repository.NewIndex()
+	idx2.Store(blob2)
+
+	mIdx := repository.NewMasterIndex()
+	mIdx.Insert(idx1)
+	mIdx.Insert(idx2)
+
+	blobs, found := mIdx.Lookup(idInIdx1, restic.DataBlob)
+	rtest.Assert(t, found, "Expected to find blob id %v from index 1", idInIdx1)
+	rtest.Equals(t, []restic.PackedBlob{blob1}, blobs)
+
+	blobs, found = mIdx.Lookup(idInIdx2, restic.DataBlob)
+	rtest.Assert(t, found, "Expected to find blob id %v from index 2", idInIdx2)
+	rtest.Equals(t, []restic.PackedBlob{blob2}, blobs)
+
+	blobs, found = mIdx.Lookup(restic.NewRandomID(), restic.DataBlob)
+	rtest.Assert(t, !found, "Expected to not find a blob when fetching with a random id")
+	rtest.Assert(t, blobs == nil, "Expected no blobs when fetching with a random id")
+}
+
+func BenchmarkMasterIndexLookupSingleIndex(b *testing.B) {
+	idx1, lookupID := createRandomIndex(rand.New(rand.NewSource(0)))
+
+	mIdx := repository.NewMasterIndex()
+	mIdx.Insert(idx1)
+
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		mIdx.Lookup(lookupID, restic.DataBlob)
+	}
+}
+
+func BenchmarkMasterIndexLookupMultipleIndex(b *testing.B) {
+	rng := rand.New(rand.NewSource(0))
+	mIdx := repository.NewMasterIndex()
+
+	for i := 0; i < 5; i++ {
+		idx, _ := createRandomIndex(rand.New(rng))
+		mIdx.Insert(idx)
+	}
+
+	idx1, lookupID := createRandomIndex(rand.New(rng))
+	mIdx.Insert(idx1)
+
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		mIdx.Lookup(lookupID, restic.DataBlob)
+	}
+}
+
+func BenchmarkMasterIndexLookupSingleIndexUnknown(b *testing.B) {
+	lookupID := restic.NewRandomID()
+	idx1, _ := createRandomIndex(rand.New(rand.NewSource(0)))
+
+	mIdx := repository.NewMasterIndex()
+	mIdx.Insert(idx1)
+
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		mIdx.Lookup(lookupID, restic.DataBlob)
+	}
+}
+
+func BenchmarkMasterIndexLookupMultipleIndexUnknown(b *testing.B) {
+	rng := rand.New(rand.NewSource(0))
+	lookupID := restic.NewRandomID()
+	mIdx := repository.NewMasterIndex()
+
+	for i := 0; i < 5; i++ {
+		idx, _ := createRandomIndex(rand.New(rng))
+		mIdx.Insert(idx)
+	}
+
+	idx1, _ := createRandomIndex(rand.New(rng))
+	mIdx.Insert(idx1)
+
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		mIdx.Lookup(lookupID, restic.DataBlob)
+	}
+}

internal/repository/repack_test.go

@@ -114,9 +114,9 @@ func findPacksForBlobs(t *testing.T, repo restic.Repository, blobs restic.BlobSe
 
 	idx := repo.Index()
 	for h := range blobs {
-		list, err := idx.Lookup(h.ID, h.Type)
+		list, found := idx.Lookup(h.ID, h.Type)
-		if err != nil {
+		if !found {
-			t.Fatal(err)
+			t.Fatal("Failed to find blob", h.ID.Str(), "with type", h.Type)
 		}
 
 		for _, pb := range list {
@@ -215,8 +215,8 @@ func TestRepack(t *testing.T) {
 	idx := repo.Index()
 
 	for h := range keepBlobs {
-		list, err := idx.Lookup(h.ID, h.Type)
+		list, found := idx.Lookup(h.ID, h.Type)
-		if err != nil {
+		if !found {
 			t.Errorf("unable to find blob %v in repo", h.ID.Str())
 			continue
 		}
@@ -234,7 +234,7 @@ func TestRepack(t *testing.T) {
 	}
 
 	for h := range removeBlobs {
-		if _, err := idx.Lookup(h.ID, h.Type); err == nil {
+		if _, found := idx.Lookup(h.ID, h.Type); found {
 			t.Errorf("blob %v still contained in the repo", h)
 		}
 	}

internal/repository/repository.go

@@ -115,10 +115,10 @@ func (r *Repository) loadBlob(ctx context.Context, id restic.ID, t restic.BlobTy
 	debug.Log("load %v with id %v (buf len %v, cap %d)", t, id.Str(), len(plaintextBuf), cap(plaintextBuf))
 
 	// lookup packs
-	blobs, err := r.idx.Lookup(id, t)
+	blobs, found := r.idx.Lookup(id, t)
-	if err != nil {
+	if !found {
-		debug.Log("id %v not found in index: %v", id.Str(), err)
+		debug.Log("id %v not found in index", id.Str())
-		return 0, err
+		return 0, errors.Errorf("id %v not found in repository", id)
 	}
 
 	// try cached pack files first
@@ -193,7 +193,7 @@ func (r *Repository) LoadJSONUnpacked(ctx context.Context, t restic.FileType, id
 }
 
 // LookupBlobSize returns the size of blob id.
-func (r *Repository) LookupBlobSize(id restic.ID, tpe restic.BlobType) (uint, error) {
+func (r *Repository) LookupBlobSize(id restic.ID, tpe restic.BlobType) (uint, bool) {
 	return r.idx.LookupSize(id, tpe)
 }
 
@@ -588,9 +588,9 @@ func (r *Repository) Close() error {
 // space.
 func (r *Repository) LoadBlob(ctx context.Context, t restic.BlobType, id restic.ID, buf []byte) (int, error) {
 	debug.Log("load blob %v into buf (len %v, cap %v)", id.Str(), len(buf), cap(buf))
-	size, err := r.idx.LookupSize(id, t)
+	size, found := r.idx.LookupSize(id, t)
-	if err != nil {
+	if !found {
-		return 0, err
+		return 0, errors.Errorf("id %v not found in repository", id)
 	}
 
 	if cap(buf) < restic.CiphertextLength(int(size)) {
@@ -622,9 +622,9 @@ func (r *Repository) SaveBlob(ctx context.Context, t restic.BlobType, buf []byte
 func (r *Repository) LoadTree(ctx context.Context, id restic.ID) (*restic.Tree, error) {
 	debug.Log("load tree %v", id.Str())
 
-	size, err := r.idx.LookupSize(id, restic.TreeBlob)
+	size, found := r.idx.LookupSize(id, restic.TreeBlob)
-	if err != nil {
+	if !found {
-		return nil, err
+		return nil, errors.Errorf("tree %v not found in repository", id)
 	}
 
 	debug.Log("size is %d, create buffer", size)

internal/restic/node.go

@@ -285,9 +285,9 @@ func (node Node) createFileAt(ctx context.Context, path string, repo Repository,
 func (node Node) writeNodeContent(ctx context.Context, repo Repository, f *os.File) error {
 	var buf []byte
 	for _, id := range node.Content {
-		size, err := repo.LookupBlobSize(id, DataBlob)
+		size, found := repo.LookupBlobSize(id, DataBlob)
-		if err != nil {
+		if !found {
-			return err
+			return errors.Errorf("id %v not found in repository", id)
 		}
 
 		buf = buf[:cap(buf)]

internal/restic/repository.go

@@ -24,7 +24,7 @@ type Repository interface {
 
 	Config() Config
 
-	LookupBlobSize(ID, BlobType) (uint, error)
+	LookupBlobSize(ID, BlobType) (uint, bool)
 
 	List(context.Context, FileType) <-chan ID
 	ListPack(context.Context, ID) ([]Blob, int64, error)
@@ -52,7 +52,7 @@ type Lister interface {
 // Index keeps track of the blobs are stored within files.
 type Index interface {
 	Has(ID, BlobType) bool
-	Lookup(ID, BlobType) ([]PackedBlob, error)
+	Lookup(ID, BlobType) ([]PackedBlob, bool)
 	Count(BlobType) uint
 
 	// Each returns a channel that yields all blobs known to the index. When