storage: refactor key_index

storage/index.go

@@ -8,16 +8,11 @@ import (
 )
 
 type index interface {
-	Get(key []byte, atIndex uint64) (index uint64, err error)
-	Range(key, end []byte, atIndex uint64) []kipair
-	Put(key []byte, index uint64)
-	Tombstone(key []byte, index uint64) error
-	Compact(index uint64) map[uint64]struct{}
-}
-
-type kipair struct {
-	index uint64
-	key   []byte
+	Get(key []byte, atRev int64) (rev reversion, err error)
+	Range(key, end []byte, atRev int64) ([][]byte, []reversion)
+	Put(key []byte, rev reversion)
+	Tombstone(key []byte, rev reversion) error
+	Compact(rev int64) map[reversion]struct{}
 }
 
 type treeIndex struct {
@@ -31,47 +26,46 @@ func newTreeIndex() index {
 	}
 }
 
-func (ti *treeIndex) Put(key []byte, index uint64) {
+func (ti *treeIndex) Put(key []byte, rev reversion) {
 	keyi := &keyIndex{key: key}
 
 	ti.Lock()
 	defer ti.Unlock()
 	item := ti.tree.Get(keyi)
 	if item == nil {
-		keyi.put(index)
+		keyi.put(rev.main, rev.sub)
 		ti.tree.ReplaceOrInsert(keyi)
 		return
 	}
 	okeyi := item.(*keyIndex)
-	okeyi.put(index)
+	okeyi.put(rev.main, rev.sub)
 }
 
-func (ti *treeIndex) Get(key []byte, atIndex uint64) (index uint64, err error) {
+func (ti *treeIndex) Get(key []byte, atRev int64) (rev reversion, err error) {
 	keyi := &keyIndex{key: key}
 
 	ti.RLock()
 	defer ti.RUnlock()
 	item := ti.tree.Get(keyi)
 	if item == nil {
-		return 0, ErrIndexNotFound
+		return reversion{}, ErrReversionNotFound
 	}
 
 	keyi = item.(*keyIndex)
-	return keyi.get(atIndex)
+	return keyi.get(atRev)
 }
 
-func (ti *treeIndex) Range(key, end []byte, atIndex uint64) []kipair {
+func (ti *treeIndex) Range(key, end []byte, atRev int64) (keys [][]byte, revs []reversion) {
 	if end == nil {
-		index, err := ti.Get(key, atIndex)
+		rev, err := ti.Get(key, atRev)
 		if err != nil {
-			return nil
+			return nil, nil
 		}
-		return []kipair{{key: key, index: index}}
+		return [][]byte{key}, []reversion{rev}
 	}
 
 	keyi := &keyIndex{key: key}
 	endi := &keyIndex{key: end}
-	pairs := make([]kipair, 0)
 
 	ti.RLock()
 	defer ti.RUnlock()
@@ -81,41 +75,42 @@ func (ti *treeIndex) Range(key, end []byte, atIndex uint64) []kipair {
 			return false
 		}
 		curKeyi := item.(*keyIndex)
-		index, err := curKeyi.get(atIndex)
+		rev, err := curKeyi.get(atRev)
 		if err != nil {
 			return true
 		}
-		pairs = append(pairs, kipair{index, curKeyi.key})
+		revs = append(revs, rev)
+		keys = append(keys, curKeyi.key)
 		return true
 	})
 
-	return pairs
+	return keys, revs
 }
 
-func (ti *treeIndex) Tombstone(key []byte, index uint64) error {
+func (ti *treeIndex) Tombstone(key []byte, rev reversion) error {
 	keyi := &keyIndex{key: key}
 
 	ti.Lock()
 	defer ti.Unlock()
 	item := ti.tree.Get(keyi)
 	if item == nil {
-		return ErrIndexNotFound
+		return ErrReversionNotFound
 	}
 
 	ki := item.(*keyIndex)
-	ki.tombstone(index)
+	ki.tombstone(rev.main, rev.sub)
 	return nil
 }
 
-func (ti *treeIndex) Compact(index uint64) map[uint64]struct{} {
-	available := make(map[uint64]struct{})
+func (ti *treeIndex) Compact(rev int64) map[reversion]struct{} {
+	available := make(map[reversion]struct{})
 	emptyki := make([]*keyIndex, 0)
-	log.Printf("store.index: compact %d", index)
+	log.Printf("store.index: compact %d", rev)
 	// TODO: do not hold the lock for long time?
 	// This is probably OK. Compacting 10M keys takes O(10ms).
 	ti.Lock()
 	defer ti.Unlock()
-	ti.tree.Ascend(compactIndex(index, available, &emptyki))
+	ti.tree.Ascend(compactIndex(rev, available, &emptyki))
 	for _, ki := range emptyki {
 		item := ti.tree.Delete(ki)
 		if item == nil {
@@ -125,10 +120,10 @@ func (ti *treeIndex) Compact(index uint64) map[uint64]struct{} {
 	return available
 }
 
-func compactIndex(index uint64, available map[uint64]struct{}, emptyki *[]*keyIndex) func(i btree.Item) bool {
+func compactIndex(rev int64, available map[reversion]struct{}, emptyki *[]*keyIndex) func(i btree.Item) bool {
 	return func(i btree.Item) bool {
 		keyi := i.(*keyIndex)
-		keyi.compact(index, available)
+		keyi.compact(rev, available)
 		if keyi.isEmpty() {
 			*emptyki = append(*emptyki, keyi)
 		}

storage/index_test.go

@@ -9,20 +9,20 @@ func TestIndexPutAndGet(t *testing.T) {
 	index := newTestTreeIndex()
 
 	tests := []T{
-		{[]byte("foo"), 0, ErrIndexNotFound, 0},
+		{[]byte("foo"), 0, ErrReversionNotFound, 0},
 		{[]byte("foo"), 1, nil, 1},
 		{[]byte("foo"), 3, nil, 1},
 		{[]byte("foo"), 5, nil, 5},
 		{[]byte("foo"), 6, nil, 5},
 
-		{[]byte("foo1"), 0, ErrIndexNotFound, 0},
-		{[]byte("foo1"), 1, ErrIndexNotFound, 0},
+		{[]byte("foo1"), 0, ErrReversionNotFound, 0},
+		{[]byte("foo1"), 1, ErrReversionNotFound, 0},
 		{[]byte("foo1"), 2, nil, 2},
 		{[]byte("foo1"), 5, nil, 2},
 		{[]byte("foo1"), 6, nil, 6},
 
-		{[]byte("foo2"), 0, ErrIndexNotFound, 0},
-		{[]byte("foo2"), 1, ErrIndexNotFound, 0},
+		{[]byte("foo2"), 0, ErrReversionNotFound, 0},
+		{[]byte("foo2"), 1, ErrReversionNotFound, 0},
 		{[]byte("foo2"), 3, nil, 3},
 		{[]byte("foo2"), 4, nil, 4},
 		{[]byte("foo2"), 6, nil, 4},
@@ -34,31 +34,26 @@ func TestContinuousCompact(t *testing.T) {
 	index := newTestTreeIndex()
 
 	tests := []T{
-		{[]byte("foo"), 0, ErrIndexNotFound, 0},
+		{[]byte("foo"), 0, ErrReversionNotFound, 0},
 		{[]byte("foo"), 1, nil, 1},
 		{[]byte("foo"), 3, nil, 1},
 		{[]byte("foo"), 5, nil, 5},
 		{[]byte("foo"), 6, nil, 5},
 
-		{[]byte("foo1"), 0, ErrIndexNotFound, 0},
-		{[]byte("foo1"), 1, ErrIndexNotFound, 0},
+		{[]byte("foo1"), 0, ErrReversionNotFound, 0},
+		{[]byte("foo1"), 1, ErrReversionNotFound, 0},
 		{[]byte("foo1"), 2, nil, 2},
 		{[]byte("foo1"), 5, nil, 2},
 		{[]byte("foo1"), 6, nil, 6},
 
-		{[]byte("foo2"), 0, ErrIndexNotFound, 0},
-		{[]byte("foo2"), 1, ErrIndexNotFound, 0},
+		{[]byte("foo2"), 0, ErrReversionNotFound, 0},
+		{[]byte("foo2"), 1, ErrReversionNotFound, 0},
 		{[]byte("foo2"), 3, nil, 3},
 		{[]byte("foo2"), 4, nil, 4},
 		{[]byte("foo2"), 6, nil, 4},
 	}
-	wa := map[uint64]struct{}{
-		1: struct{}{},
-		2: struct{}{},
-		3: struct{}{},
-		4: struct{}{},
-		5: struct{}{},
-		6: struct{}{},
+	wa := map[reversion]struct{}{
+		reversion{main: 1}: struct{}{},
 	}
 	ga := index.Compact(1)
 	if !reflect.DeepEqual(ga, wa) {
@@ -66,72 +61,96 @@ func TestContinuousCompact(t *testing.T) {
 	}
 	verify(t, index, tests)
 
+	wa = map[reversion]struct{}{
+		reversion{main: 1}: struct{}{},
+		reversion{main: 2}: struct{}{},
+	}
 	ga = index.Compact(2)
 	if !reflect.DeepEqual(ga, wa) {
 		t.Errorf("a = %v, want %v", ga, wa)
 	}
 	verify(t, index, tests)
 
+	wa = map[reversion]struct{}{
+		reversion{main: 1}: struct{}{},
+		reversion{main: 2}: struct{}{},
+		reversion{main: 3}: struct{}{},
+	}
 	ga = index.Compact(3)
 	if !reflect.DeepEqual(ga, wa) {
 		t.Errorf("a = %v, want %v", ga, wa)
 	}
 	verify(t, index, tests)
 
+	wa = map[reversion]struct{}{
+		reversion{main: 1}: struct{}{},
+		reversion{main: 2}: struct{}{},
+		reversion{main: 4}: struct{}{},
+	}
 	ga = index.Compact(4)
-	delete(wa, 3)
-	tests[12] = T{[]byte("foo2"), 3, ErrIndexNotFound, 0}
+	delete(wa, reversion{main: 3})
+	tests[12] = T{[]byte("foo2"), 3, ErrReversionNotFound, 0}
 	if !reflect.DeepEqual(wa, ga) {
 		t.Errorf("a = %v, want %v", ga, wa)
 	}
 	verify(t, index, tests)
 
+	wa = map[reversion]struct{}{
+		reversion{main: 2}: struct{}{},
+		reversion{main: 4}: struct{}{},
+		reversion{main: 5}: struct{}{},
+	}
 	ga = index.Compact(5)
-	delete(wa, 1)
+	delete(wa, reversion{main: 1})
 	if !reflect.DeepEqual(ga, wa) {
 		t.Errorf("a = %v, want %v", ga, wa)
 	}
-	tests[1] = T{[]byte("foo"), 1, ErrIndexNotFound, 0}
-	tests[2] = T{[]byte("foo"), 3, ErrIndexNotFound, 0}
+	tests[1] = T{[]byte("foo"), 1, ErrReversionNotFound, 0}
+	tests[2] = T{[]byte("foo"), 3, ErrReversionNotFound, 0}
 	verify(t, index, tests)
 
+	wa = map[reversion]struct{}{
+		reversion{main: 4}: struct{}{},
+		reversion{main: 5}: struct{}{},
+		reversion{main: 6}: struct{}{},
+	}
 	ga = index.Compact(6)
-	delete(wa, 2)
+	delete(wa, reversion{main: 2})
 	if !reflect.DeepEqual(ga, wa) {
 		t.Errorf("a = %v, want %v", ga, wa)
 	}
-	tests[7] = T{[]byte("foo1"), 2, ErrIndexNotFound, 0}
-	tests[8] = T{[]byte("foo1"), 5, ErrIndexNotFound, 0}
+	tests[7] = T{[]byte("foo1"), 2, ErrReversionNotFound, 0}
+	tests[8] = T{[]byte("foo1"), 5, ErrReversionNotFound, 0}
 	verify(t, index, tests)
 }
 
 func verify(t *testing.T, index index, tests []T) {
 	for i, tt := range tests {
-		h, err := index.Get(tt.key, tt.index)
+		h, err := index.Get(tt.key, tt.rev)
 		if err != tt.werr {
 			t.Errorf("#%d: err = %v, want %v", i, err, tt.werr)
 		}
-		if h != tt.windex {
-			t.Errorf("#%d: index = %d, want %d", i, h, tt.windex)
+		if h.main != tt.wrev {
+			t.Errorf("#%d: rev = %d, want %d", i, h.main, tt.wrev)
 		}
 	}
 }
 
 type T struct {
-	key   []byte
-	index uint64
+	key []byte
+	rev int64
 
-	werr   error
-	windex uint64
+	werr error
+	wrev int64
 }
 
 func newTestTreeIndex() index {
 	index := newTreeIndex()
-	index.Put([]byte("foo"), 1)
-	index.Put([]byte("foo1"), 2)
-	index.Put([]byte("foo2"), 3)
-	index.Put([]byte("foo2"), 4)
-	index.Put([]byte("foo"), 5)
-	index.Put([]byte("foo1"), 6)
+	index.Put([]byte("foo"), reversion{main: 1})
+	index.Put([]byte("foo1"), reversion{main: 2})
+	index.Put([]byte("foo2"), reversion{main: 3})
+	index.Put([]byte("foo2"), reversion{main: 4})
+	index.Put([]byte("foo"), reversion{main: 5})
+	index.Put([]byte("foo1"), reversion{main: 6})
 	return index
 }

storage/key_index.go

@@ -3,33 +3,34 @@ package storage
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"log"
 
 	"github.com/coreos/etcd/Godeps/_workspace/src/github.com/google/btree"
 )
 
 var (
-	ErrIndexNotFound = errors.New("index: not found")
+	ErrReversionNotFound = errors.New("stroage: Reversion not found")
 )
 
-// keyIndex stores the index of an key in the backend.
+// keyIndex stores the reversion of an key in the backend.
 // Each keyIndex has at least one key generation.
 // Each generation might have several key versions.
 // Tombstone on a key appends an tombstone version at the end
 // of the current generation and creates a new empty generation.
 // Each version of a key has an index pointing to the backend.
 //
-// For example: put(1);put(2);tombstone(3);put(4);tombstone(5) on key "foo"
+// For example: put(1.0);put(2.0);tombstone(3.0);put(4.0);tombstone(5.0) on key "foo"
 // generate a keyIndex:
 // key:     "foo"
-// index: 5
+// rev: 5
 // generations:
 //    {empty}
-//    {4, 5(t)}
-//    {1, 2, 3(t)}
+//    {4.0, 5.0(t)}
+//    {1.0, 2.0, 3.0(t)}
 //
 // Compact a keyIndex removes the versions with smaller or equal to
-// index except the largest one. If the generations becomes empty
+// rev except the largest one. If the generations becomes empty
 // during compaction, it will be removed. if all the generations get
 // removed, the keyIndex Should be removed.
 
@@ -37,115 +38,125 @@ var (
 // compact(2) on the previous example
 // generations:
 //    {empty}
-//    {4, 5(t)}
-//    {2, 3(t)}
+//    {4.0, 5.0(t)}
+//    {2.0, 3.0(t)}
 //
 // compact(4)
 // generations:
 //    {empty}
-//    {4, 5(t)}
+//    {4.0, 5.0(t)}
 //
 // compact(5):
 // generations:
-//    {empty}
-//    {5(t)}
+//    {empty} -> key SHOULD be removed.
 //
 // compact(6):
 // generations:
 //    {empty} -> key SHOULD be removed.
 type keyIndex struct {
 	key         []byte
-	index       uint64
+	rev         int64
 	generations []generation
 }
 
-// put puts an index to the keyIndex.
-func (ki *keyIndex) put(index uint64) {
-	if index < ki.index {
-		log.Panicf("store.keyindex: put with unexpected smaller index [%d / %d]", index, ki.index)
+// put puts a reversion to the keyIndex.
+func (ki *keyIndex) put(rev int64, subrev int64) {
+	if rev < ki.rev {
+		log.Panicf("store.keyindex: put with unexpected smaller reversion [%d / %d]", rev, ki.rev)
 	}
 	if len(ki.generations) == 0 {
 		ki.generations = append(ki.generations, generation{})
 	}
 	g := &ki.generations[len(ki.generations)-1]
-	g.cont = append(g.cont, index)
+	g.revs = append(g.revs, reversion{rev, subrev})
 	g.ver++
-	ki.index = index
+	ki.rev = rev
 }
 
-// tombstone puts an index, pointing to a tombstone, to the keyIndex.
+// tombstone puts a reversion, pointing to a tombstone, to the keyIndex.
 // It also creates a new empty generation in the keyIndex.
-func (ki *keyIndex) tombstone(index uint64) {
+func (ki *keyIndex) tombstone(rev int64, subrev int64) {
 	if ki.isEmpty() {
 		log.Panicf("store.keyindex: unexpected tombstone on empty keyIndex %s", string(ki.key))
 	}
-	ki.put(index)
+	ki.put(rev, subrev)
 	ki.generations = append(ki.generations, generation{})
 }
 
-// get gets the index of thk that satisfies the given atIndex.
-// Index must be lower or equal to the given atIndex.
-func (ki *keyIndex) get(atIndex uint64) (index uint64, err error) {
+// get gets the reversion of the key that satisfies the given atRev.
+// Rev must be higher than or equal to the given atRev.
+func (ki *keyIndex) get(atRev int64) (rev reversion, err error) {
 	if ki.isEmpty() {
 		log.Panicf("store.keyindex: unexpected get on empty keyIndex %s", string(ki.key))
 	}
-	g := ki.findGeneration(atIndex)
+	g := ki.findGeneration(atRev)
 	if g.isEmpty() {
-		return 0, ErrIndexNotFound
+		return reversion{}, ErrReversionNotFound
 	}
 
-	f := func(index, ver uint64) bool {
-		if index <= atIndex {
+	f := func(rev reversion) bool {
+		if rev.main <= atRev {
 			return false
 		}
 		return true
 	}
 
-	_, n := g.walk(f)
+	n := g.walk(f)
 	if n != -1 {
-		return g.cont[n], nil
+		return g.revs[n], nil
 	}
-	return 0, ErrIndexNotFound
+
+	return reversion{}, ErrReversionNotFound
 }
 
 // compact compacts a keyIndex by removing the versions with smaller or equal
-// index than the given atIndex except the largest one.
+// reversion than the given atRev except the largest one (If the largest one is
+// a tombstone, it will not be kept).
 // If a generation becomes empty during compaction, it will be removed.
-func (ki *keyIndex) compact(atIndex uint64, available map[uint64]struct{}) {
+func (ki *keyIndex) compact(atRev int64, available map[reversion]struct{}) {
 	if ki.isEmpty() {
 		log.Panic("store.keyindex: unexpected compact on empty keyIndex %s", string(ki.key))
 	}
-	// walk until reaching the first content that has an index smaller or equal to
-	// the atIndex.
-	// add all the reached indexes into available map.
-	f := func(index, _ uint64) bool {
-		available[index] = struct{}{}
-		if index <= atIndex {
+
+	// walk until reaching the first reversion that has an reversion smaller or equal to
+	// the atReversion.
+	// add it to the available map
+	f := func(rev reversion) bool {
+		if rev.main <= atRev {
+			available[rev] = struct{}{}
 			return false
 		}
 		return true
 	}
 
-	g := ki.findGeneration(atIndex)
-	i := len(ki.generations) - 1
-	for i >= 0 {
+	g := ki.findGeneration(atRev)
+	if g == nil {
+		return
+	}
+
+	i := 0
+	for i <= len(ki.generations)-1 {
 		wg := &ki.generations[i]
 		if wg == g {
 			break
 		}
-		wg.walk(f)
-		i--
+		i++
 	}
 
-	_, n := g.walk(f)
-
-	// remove the previous contents.
-	if n != -1 {
-		g.cont = g.cont[n:]
+	if !g.isEmpty() {
+		n := g.walk(f)
+		// remove the previous contents.
+		if n != -1 {
+			g.revs = g.revs[n:]
+		}
+		// remove any tombstone
+		if len(g.revs) == 1 && i != len(ki.generations)-1 {
+			delete(available, g.revs[0])
+			i++
+		}
 	}
 	// remove the previous generations.
 	ki.generations = ki.generations[i:]
-
 	return
 }
 
@@ -155,51 +166,63 @@ func (ki *keyIndex) isEmpty() bool {
 
 // findGeneartion finds out the generation of the keyIndex that the
 // given index belongs to.
-func (ki *keyIndex) findGeneration(index uint64) *generation {
-	g, youngerg := len(ki.generations)-1, len(ki.generations)-2
-
-	// If the head index of a younger generation is smaller than
-	// the given index, the index cannot be in the younger
-	// generation.
-	for youngerg >= 0 && ki.generations[youngerg].cont != nil {
-		yg := ki.generations[youngerg]
-		if yg.cont[len(yg.cont)-1] < index {
-			break
+func (ki *keyIndex) findGeneration(rev int64) *generation {
+	cg := len(ki.generations) - 1
+
+	for cg >= 0 {
+		if len(ki.generations[cg].revs) == 0 {
+			cg--
+			continue
 		}
-		g--
-		youngerg--
-	}
-	if g < 0 {
-		return nil
+		g := ki.generations[cg]
+		if g.revs[0].main <= rev {
+			return &ki.generations[cg]
+		}
+		cg--
 	}
-	return &ki.generations[g]
+	return nil
 }
 
 func (a *keyIndex) Less(b btree.Item) bool {
 	return bytes.Compare(a.key, b.(*keyIndex).key) == -1
 }
 
+func (ki *keyIndex) String() string {
+	var s string
+	for _, g := range ki.generations {
+		s += g.String()
+	}
+	return s
+}
+
 type generation struct {
-	ver  uint64
-	cont []uint64
+	ver  int64
+	revs []reversion
+}
+
+type reversion struct {
+	main int64
+	sub  int64
 }
 
-func (g *generation) isEmpty() bool { return len(g.cont) == 0 }
+func (g *generation) isEmpty() bool { return g == nil || len(g.revs) == 0 }
 
-// walk walks through the (index, version) pairs in the generation in ascending order.
-// It passes the (index, version) to the given function.
+// walk walks through the reversions in the generation in ascending order.
+// It passes the revision to the given function.
 // walk returns until: 1. it finishs walking all pairs 2. the function returns false.
-// walk returns the (index, version) pair at where it stopped. If it stopped after
-// finishing walking, (0, -1) will be returned.
-func (g *generation) walk(f func(index, ver uint64) bool) (uint64, int) {
-	ver := g.ver
-	l := len(g.cont)
-	for i := range g.cont {
-		ok := f(g.cont[l-i-1], ver)
+// walk returns the position at where it stopped. If it stopped after
+// finishing walking, -1 will be returned.
+func (g *generation) walk(f func(rev reversion) bool) int {
+	l := len(g.revs)
+	for i := range g.revs {
+		ok := f(g.revs[l-i-1])
 		if !ok {
-			return ver, l - i - 1
+			return l - i - 1
 		}
-		ver--
 	}
-	return 0, -1
+	return -1
+}
+
+func (g *generation) String() string {
+	return fmt.Sprintf("g: ver[%d], revs %#v\n", g.ver, g.revs)
 }

storage/key_index_test.go

@@ -7,23 +7,22 @@ import (
 
 func TestKeyIndexGet(t *testing.T) {
 	// key:     "foo"
-	// index: 12
+	// rev: 12
 	// generations:
 	//    {empty}
 	//    {8[1], 10[2], 12(t)[3]}
 	//    {4[2], 6(t)[3]}
 	ki := newTestKeyIndex()
-	ki.compact(4, make(map[uint64]struct{}))
+	ki.compact(4, make(map[reversion]struct{}))
 
 	tests := []struct {
-		index uint64
+		rev int64
 
-		windex uint64
-		werr   error
+		wrev int64
+		werr error
 	}{
-		// expected not exist on an index that is greater than the last tombstone
-		{13, 0, ErrIndexNotFound},
-		{13, 0, ErrIndexNotFound},
+		{13, 12, nil},
+		{13, 12, nil},
 
 		// get on generation 2
 		{12, 12, nil},
@@ -31,7 +30,7 @@ func TestKeyIndexGet(t *testing.T) {
 		{10, 10, nil},
 		{9, 8, nil},
 		{8, 8, nil},
-		{7, 0, ErrIndexNotFound},
+		{7, 6, nil},
 
 		// get on generation 1
 		{6, 6, nil},
@@ -40,35 +39,35 @@ func TestKeyIndexGet(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		index, err := ki.get(tt.index)
+		rev, err := ki.get(tt.rev)
 		if err != tt.werr {
 			t.Errorf("#%d: err = %v, want %v", i, err, tt.werr)
 		}
-		if index != tt.windex {
-			t.Errorf("#%d: index = %d, want %d", i, index, tt.index)
+		if rev.main != tt.wrev {
+			t.Errorf("#%d: rev = %d, want %d", i, rev.main, tt.rev)
 		}
 	}
 }
 
 func TestKeyIndexPut(t *testing.T) {
 	ki := &keyIndex{key: []byte("foo")}
-	ki.put(5)
+	ki.put(5, 0)
 
 	wki := &keyIndex{
 		key:         []byte("foo"),
-		index:       5,
-		generations: []generation{{ver: 1, cont: []uint64{5}}},
+		rev:         5,
+		generations: []generation{{ver: 1, revs: []reversion{{main: 5}}}},
 	}
 	if !reflect.DeepEqual(ki, wki) {
 		t.Errorf("ki = %+v, want %+v", ki, wki)
 	}
 
-	ki.put(7)
+	ki.put(7, 0)
 
 	wki = &keyIndex{
 		key:         []byte("foo"),
-		index:       7,
-		generations: []generation{{ver: 2, cont: []uint64{5, 7}}},
+		rev:         7,
+		generations: []generation{{ver: 2, revs: []reversion{{main: 5}, {main: 7}}}},
 	}
 	if !reflect.DeepEqual(ki, wki) {
 		t.Errorf("ki = %+v, want %+v", ki, wki)
@@ -77,27 +76,31 @@ func TestKeyIndexPut(t *testing.T) {
 
 func TestKeyIndexTombstone(t *testing.T) {
 	ki := &keyIndex{key: []byte("foo")}
-	ki.put(5)
+	ki.put(5, 0)
 
-	ki.tombstone(7)
+	ki.tombstone(7, 0)
 
 	wki := &keyIndex{
 		key:         []byte("foo"),
-		index:       7,
-		generations: []generation{{ver: 2, cont: []uint64{5, 7}}, {}},
+		rev:         7,
+		generations: []generation{{ver: 2, revs: []reversion{{main: 5}, {main: 7}}}, {}},
 	}
 	if !reflect.DeepEqual(ki, wki) {
 		t.Errorf("ki = %+v, want %+v", ki, wki)
 	}
 
-	ki.put(8)
-	ki.put(9)
-	ki.tombstone(15)
+	ki.put(8, 0)
+	ki.put(9, 0)
+	ki.tombstone(15, 0)
 
 	wki = &keyIndex{
-		key:         []byte("foo"),
-		index:       15,
-		generations: []generation{{ver: 2, cont: []uint64{5, 7}}, {ver: 3, cont: []uint64{8, 9, 15}}, {}},
+		key: []byte("foo"),
+		rev: 15,
+		generations: []generation{
+			{ver: 2, revs: []reversion{{main: 5}, {main: 7}}},
+			{ver: 3, revs: []reversion{{main: 8}, {main: 9}, {main: 15}}},
+			{},
+		},
 	}
 	if !reflect.DeepEqual(ki, wki) {
 		t.Errorf("ki = %+v, want %+v", ki, wki)
@@ -106,221 +109,192 @@ func TestKeyIndexTombstone(t *testing.T) {
 
 func TestKeyIndexCompact(t *testing.T) {
 	tests := []struct {
-		compact uint64
+		compact int64
 
 		wki *keyIndex
-		wam map[uint64]struct{}
+		wam map[reversion]struct{}
 	}{
 		{
 			1,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{2, 4, 6}},
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 2}, {main: 4}, {main: 6}}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				2: struct{}{}, 4: struct{}{}, 6: struct{}{},
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
-			},
+			map[reversion]struct{}{},
 		},
 		{
 			2,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{2, 4, 6}},
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 2}, {main: 4}, {main: 6}}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				2: struct{}{}, 4: struct{}{}, 6: struct{}{},
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 2}: struct{}{},
 			},
 		},
 		{
 			3,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{2, 4, 6}},
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 2}, {main: 4}, {main: 6}}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				2: struct{}{}, 4: struct{}{}, 6: struct{}{},
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 2}: struct{}{},
 			},
 		},
 		{
 			4,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{4, 6}},
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 4}, {main: 6}}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				4: struct{}{}, 6: struct{}{},
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 4}: struct{}{},
 			},
 		},
 		{
 			5,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{4, 6}},
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 4}, {main: 6}}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				4: struct{}{}, 6: struct{}{},
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 4}: struct{}{},
 			},
 		},
 		{
 			6,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{6}},
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				6: struct{}{},
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
-			},
+			map[reversion]struct{}{},
 		},
 		{
 			7,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
-			},
+			map[reversion]struct{}{},
 		},
 		{
 			8,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 8}: struct{}{},
 			},
 		},
 		{
 			9,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{8, 10, 12}},
+					{ver: 3, revs: []reversion{{main: 8}, {main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				8: struct{}{}, 10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 8}: struct{}{},
 			},
 		},
 		{
 			10,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{10, 12}},
+					{ver: 3, revs: []reversion{{main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 10}: struct{}{},
 			},
 		},
 		{
 			11,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
+				key: []byte("foo"),
+				rev: 12,
 				generations: []generation{
-					{ver: 3, cont: []uint64{10, 12}},
+					{ver: 3, revs: []reversion{{main: 10}, {main: 12}}},
 					{},
 				},
 			},
-			map[uint64]struct{}{
-				10: struct{}{}, 12: struct{}{},
+			map[reversion]struct{}{
+				reversion{main: 10}: struct{}{},
 			},
 		},
 		{
 			12,
 			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
-				generations: []generation{
-					{ver: 3, cont: []uint64{12}},
-					{},
-				},
-			},
-			map[uint64]struct{}{
-				12: struct{}{},
-			},
-		},
-		{
-			13,
-			&keyIndex{
-				key:   []byte("foo"),
-				index: 12,
-				generations: []generation{
-					{},
-				},
+				key:         []byte("foo"),
+				rev:         12,
+				generations: []generation{{}},
 			},
-			map[uint64]struct{}{},
+			map[reversion]struct{}{},
 		},
 	}
 
 	// Continous Compaction
 	ki := newTestKeyIndex()
 	for i, tt := range tests {
-		am := make(map[uint64]struct{})
+		am := make(map[reversion]struct{})
 		ki.compact(tt.compact, am)
 		if !reflect.DeepEqual(ki, tt.wki) {
 			t.Errorf("#%d: ki = %+v, want %+v", i, ki, tt.wki)
 		}
 		if !reflect.DeepEqual(am, tt.wam) {
-			t.Errorf("#%d: am = %+v, want %+v", am, tt.wam)
+			t.Errorf("#%d: am = %+v, want %+v", i, am, tt.wam)
 		}
 	}
 
 	// Jump Compaction
 	for i, tt := range tests {
 		if (i%2 == 0 && i < 6) && (i%2 == 1 && i > 6) {
-			am := make(map[uint64]struct{})
+			am := make(map[reversion]struct{})
 			ki.compact(tt.compact, am)
 			if !reflect.DeepEqual(ki, tt.wki) {
 				t.Errorf("#%d: ki = %+v, want %+v", i, ki, tt.wki)
@@ -334,31 +308,31 @@ func TestKeyIndexCompact(t *testing.T) {
 	// OnceCompaction
 	for i, tt := range tests {
 		ki := newTestKeyIndex()
-		am := make(map[uint64]struct{})
+		am := make(map[reversion]struct{})
 		ki.compact(tt.compact, am)
 		if !reflect.DeepEqual(ki, tt.wki) {
 			t.Errorf("#%d: ki = %+v, want %+v", i, ki, tt.wki)
 		}
 		if !reflect.DeepEqual(am, tt.wam) {
-			t.Errorf("#%d: am = %+v, want %+v", am, tt.wam)
+			t.Errorf("#%d: am = %+v, want %+v", i, am, tt.wam)
 		}
 	}
 }
 
 func newTestKeyIndex() *keyIndex {
 	// key:     "foo"
-	// index: 12
+	// rev: 12
 	// generations:
 	//    {empty}
 	//    {8[1], 10[2], 12(t)[3]}
 	//    {2[1], 4[2], 6(t)[3]}
 
 	ki := &keyIndex{key: []byte("foo")}
-	ki.put(2)
-	ki.put(4)
-	ki.tombstone(6)
-	ki.put(8)
-	ki.put(10)
-	ki.tombstone(12)
+	ki.put(2, 0)
+	ki.put(4, 0)
+	ki.tombstone(6, 0)
+	ki.put(8, 0)
+	ki.put(10, 0)
+	ki.tombstone(12, 0)
 	return ki
 }

storage/kv.go

@@ -3,33 +3,33 @@ package storage
 import "github.com/coreos/etcd/storage/storagepb"
 
 type KV interface {
-	// Range gets the keys in the range at rangeIndex.
-	// If rangeIndex <=0, range gets the keys at currentIndex.
+	// Range gets the keys in the range at rangeRev.
+	// If rangeRev <=0, range gets the keys at currentRev.
 	// If `end` is nil, the request returns the key.
 	// If `end` is not nil, it gets the keys in range [key, range_end).
 	// Limit limits the number of keys returned.
-	Range(key, end []byte, limit, rangeIndex int64) (kvs []storagepb.KeyValue, index int64)
+	Range(key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64)
 
 	// Put puts the given key,value into the store.
-	// A put also increases the index of the store, and generates one event in the event history.
-	Put(key, value []byte) (index int64)
+	// A put also increases the rev of the store, and generates one event in the event history.
+	Put(key, value []byte) (rev int64)
 
 	// DeleteRange deletes the given range from the store.
-	// A deleteRange increases the index of the store if any key in the range exists.
+	// A deleteRange increases the rev of the store if any key in the range exists.
 	// The number of key deleted will be returned.
 	// It also generates one event for each key delete in the event history.
 	// if the `end` is nil, deleteRange deletes the key.
 	// if the `end` is not nil, deleteRange deletes the keys in range [key, range_end).
-	DeleteRange(key, end []byte) (n, index int64)
+	DeleteRange(key, end []byte) (n, rev int64)
 
 	// TnxBegin begins a tnx. Only Tnx prefixed operation can be executed, others will be blocked
 	// until tnx ends. Only one on-going tnx is allowed.
 	// TnxBegin returns an int64 tnx ID.
-	// All tnx prefixed operations with same tnx ID will be done with the same index.
+	// All tnx prefixed operations with same tnx ID will be done with the same rev.
 	TnxBegin() int64
 	// TnxEnd ends the on-going tnx with tnx ID. If the on-going tnx ID is not matched, error is returned.
 	TnxEnd(tnxID int64) error
-	TnxRange(tnxID int64, key, end []byte, limit, rangeIndex int64) (kvs []storagepb.KeyValue, index int64, err error)
-	TnxPut(tnxID int64, key, value []byte) (index int64, err error)
-	TnxDeleteRange(tnxID int64, key, end []byte) (n, index int64, err error)
+	TnxRange(tnxID int64, key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error)
+	TnxPut(tnxID int64, key, value []byte) (rev int64, err error)
+	TnxDeleteRange(tnxID int64, key, end []byte) (n, rev int64, err error)
 }

storage/kvstore.go

@@ -1,7 +1,6 @@
 package storage
 
 import (
-	"bytes"
 	"encoding/binary"
 	"errors"
 	"log"
@@ -27,8 +26,7 @@ type store struct {
 	b       backend.Backend
 	kvindex index
 
-	currentIndex uint64
-	subIndex     uint32 // tracks next subIndex to put into backend
+	currentRev reversion
 
 	tmu   sync.Mutex // protect the tnxID field
 	tnxID int64      // tracks the current tnxID to verify tnx operations
@@ -36,9 +34,9 @@ type store struct {
 
 func newStore(path string) KV {
 	s := &store{
-		b:            backend.New(path, batchInterval, batchLimit),
-		kvindex:      newTreeIndex(),
-		currentIndex: 0,
+		b:          backend.New(path, batchInterval, batchLimit),
+		kvindex:    newTreeIndex(),
+		currentRev: reversion{},
 	}
 
 	tx := s.b.BatchTx()
@@ -52,31 +50,31 @@ func newStore(path string) KV {
 
 func (s *store) Put(key, value []byte) int64 {
 	id := s.TnxBegin()
-	s.put(key, value, s.currentIndex+1)
+	s.put(key, value, s.currentRev.main+1)
 	s.TnxEnd(id)
 
-	return int64(s.currentIndex)
+	return int64(s.currentRev.main)
 }
 
-func (s *store) Range(key, end []byte, limit, rangeIndex int64) (kvs []storagepb.KeyValue, index int64) {
+func (s *store) Range(key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64) {
 	id := s.TnxBegin()
-	kvs, index = s.rangeKeys(key, end, limit, rangeIndex)
+	kvs, rev = s.rangeKeys(key, end, limit, rangeRev)
 	s.TnxEnd(id)
 
-	return kvs, index
+	return kvs, rev
 }
 
-func (s *store) DeleteRange(key, end []byte) (n, index int64) {
+func (s *store) DeleteRange(key, end []byte) (n, rev int64) {
 	id := s.TnxBegin()
-	n = s.deleteRange(key, end, s.currentIndex+1)
+	n = s.deleteRange(key, end, s.currentRev.main+1)
 	s.TnxEnd(id)
 
-	return n, int64(s.currentIndex)
+	return n, int64(s.currentRev.main)
 }
 
 func (s *store) TnxBegin() int64 {
 	s.mu.Lock()
-	s.subIndex = 0
+	s.currentRev.sub = 0
 
 	s.tmu.Lock()
 	defer s.tmu.Unlock()
@@ -91,111 +89,94 @@ func (s *store) TnxEnd(tnxID int64) error {
 		return ErrTnxIDMismatch
 	}
 
-	if s.subIndex != 0 {
-		s.currentIndex += 1
+	if s.currentRev.sub != 0 {
+		s.currentRev.main += 1
 	}
-	s.subIndex = 0
+	s.currentRev.sub = 0
 	s.mu.Unlock()
 	return nil
 }
 
-func (s *store) TnxRange(tnxID int64, key, end []byte, limit, rangeIndex int64) (kvs []storagepb.KeyValue, index int64, err error) {
+func (s *store) TnxRange(tnxID int64, key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error) {
 	s.tmu.Lock()
 	defer s.tmu.Unlock()
 	if tnxID != s.tnxID {
 		return nil, 0, ErrTnxIDMismatch
 	}
-	kvs, index = s.rangeKeys(key, end, limit, rangeIndex)
-	return kvs, index, nil
+	kvs, rev = s.rangeKeys(key, end, limit, rangeRev)
+	return kvs, rev, nil
 }
 
-func (s *store) TnxPut(tnxID int64, key, value []byte) (index int64, err error) {
+func (s *store) TnxPut(tnxID int64, key, value []byte) (rev int64, err error) {
 	s.tmu.Lock()
 	defer s.tmu.Unlock()
 	if tnxID != s.tnxID {
 		return 0, ErrTnxIDMismatch
 	}
 
-	s.put(key, value, s.currentIndex+1)
-	return int64(s.currentIndex + 1), nil
+	s.put(key, value, s.currentRev.main+1)
+	return int64(s.currentRev.main + 1), nil
 }
 
-func (s *store) TnxDeleteRange(tnxID int64, key, end []byte) (n, index int64, err error) {
+func (s *store) TnxDeleteRange(tnxID int64, key, end []byte) (n, rev int64, err error) {
 	s.tmu.Lock()
 	defer s.tmu.Unlock()
 	if tnxID != s.tnxID {
 		return 0, 0, ErrTnxIDMismatch
 	}
 
-	n = s.deleteRange(key, end, s.currentIndex+1)
-	if n != 0 || s.subIndex != 0 {
-		index = int64(s.currentIndex + 1)
+	n = s.deleteRange(key, end, s.currentRev.main+1)
+	if n != 0 || s.currentRev.sub != 0 {
+		rev = int64(s.currentRev.main + 1)
 	}
-	return n, index, nil
+	return n, rev, nil
 }
 
 // range is a keyword in Go, add Keys suffix.
-func (s *store) rangeKeys(key, end []byte, limit, rangeIndex int64) (kvs []storagepb.KeyValue, index int64) {
-	if rangeIndex <= 0 {
-		index = int64(s.currentIndex)
-		if s.subIndex > 0 {
-			index += 1
+func (s *store) rangeKeys(key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64) {
+	if rangeRev <= 0 {
+		rev = int64(s.currentRev.main)
+		if s.currentRev.sub > 0 {
+			rev += 1
 		}
 	} else {
-		index = rangeIndex
+		rev = rangeRev
 	}
 
-	pairs := s.kvindex.Range(key, end, uint64(index))
-	if len(pairs) == 0 {
-		return nil, index
+	_, revs := s.kvindex.Range(key, end, int64(rev))
+	if len(revs) == 0 {
+		return nil, rev
 	}
-	if limit > 0 && len(pairs) > int(limit) {
-		pairs = pairs[:limit]
+	if limit > 0 && len(revs) > int(limit) {
+		revs = revs[:limit]
 	}
 
 	tx := s.b.BatchTx()
 	tx.Lock()
 	defer tx.Unlock()
+	for _, rev := range revs {
+		revbytes := make([]byte, 8+1+8)
+		revToBytes(rev.main, rev.sub, revbytes)
 
-	for _, pair := range pairs {
-		ibytes := make([]byte, 8)
-		endbytes := make([]byte, 8)
-		binary.BigEndian.PutUint64(ibytes, pair.index)
-		binary.BigEndian.PutUint64(endbytes, pair.index+1)
-
-		found := false
-		var kv *storagepb.KeyValue
-
-		vs := tx.UnsafeRange(keyBucketName, ibytes, endbytes, 0)
-		for _, v := range vs {
-			var e storagepb.Event
-			err := e.Unmarshal(v)
-			if err != nil {
-				log.Fatalf("storage: range cannot unmarshal event: %v", err)
-			}
-			if bytes.Equal(e.Kv.Key, pair.key) {
-				if e.Type == storagepb.PUT {
-					kv = &e.Kv
-				} else {
-					kv = nil
-				}
-				found = true
-			}
+		vs := tx.UnsafeRange(keyBucketName, revbytes, nil, 0)
+		if len(vs) != 1 {
+			log.Fatalf("storage: range cannot find rev (%d,%d)", rev.main, rev.sub)
 		}
 
-		if !found {
-			log.Fatalf("storage: range cannot find key %s at index %d", string(pair.key), pair.index)
+		e := &storagepb.Event{}
+		if err := e.Unmarshal(vs[0]); err != nil {
+			log.Fatalf("storage: cannot unmarshal event: %v", err)
 		}
-		if kv != nil {
-			kvs = append(kvs, *kv)
+		if e.Type == storagepb.PUT {
+			kvs = append(kvs, e.Kv)
 		}
 	}
-	return kvs, index
+	return kvs, rev
 }
 
-func (s *store) put(key, value []byte, index uint64) {
-	ibytes := make([]byte, 8+1+4)
-	indexToBytes(index, s.subIndex, ibytes)
+func (s *store) put(key, value []byte, rev int64) {
+	ibytes := make([]byte, 8+1+8)
+	revToBytes(rev, s.currentRev.sub, ibytes)
 
 	event := storagepb.Event{
 		Type: storagepb.PUT,
@@ -214,24 +195,24 @@ func (s *store) put(key, value []byte, index uint64) {
 	tx.Lock()
 	defer tx.Unlock()
 	tx.UnsafePut(keyBucketName, ibytes, d)
-	s.kvindex.Put(key, index)
-	s.subIndex += 1
+	s.kvindex.Put(key, reversion{main: rev, sub: s.currentRev.sub})
+	s.currentRev.sub += 1
 }
 
-func (s *store) deleteRange(key, end []byte, index uint64) int64 {
+func (s *store) deleteRange(key, end []byte, rev int64) int64 {
 	var n int64
-	rindex := index
-	if s.subIndex > 0 {
-		rindex += 1
+	rrev := rev
+	if s.currentRev.sub > 0 {
+		rrev += 1
 	}
-	pairs := s.kvindex.Range(key, end, rindex)
+	keys, _ := s.kvindex.Range(key, end, rrev)
 
-	if len(pairs) == 0 {
+	if len(keys) == 0 {
 		return 0
 	}
 
-	for _, pair := range pairs {
-		ok := s.delete(pair.key, index)
+	for _, key := range keys {
+		ok := s.delete(key, rev)
 		if ok {
 			n++
 		}
@@ -239,19 +220,39 @@ func (s *store) deleteRange(key, end []byte, index uint64) int64 {
 	return n
 }
 
-func (s *store) delete(key []byte, index uint64) bool {
-	gindex := index
-	if s.subIndex > 0 {
-		gindex += 1
+func (s *store) delete(key []byte, mainrev int64) bool {
+	grev := mainrev
+	if s.currentRev.sub > 0 {
+		grev += 1
 	}
-	_, err := s.kvindex.Get(key, gindex)
+	rev, err := s.kvindex.Get(key, grev)
 	if err != nil {
 		// key not exist
 		return false
 	}
 
-	ibytes := make([]byte, 8+1+4)
-	indexToBytes(index, s.subIndex, ibytes)
+	tx := s.b.BatchTx()
+	tx.Lock()
+	defer tx.Unlock()
+
+	revbytes := make([]byte, 8+1+8)
+	revToBytes(rev.main, rev.sub, revbytes)
+
+	vs := tx.UnsafeRange(keyBucketName, revbytes, nil, 0)
+	if len(vs) != 1 {
+		log.Fatalf("storage: delete cannot find rev (%d,%d)", rev.main, rev.sub)
+	}
+
+	e := &storagepb.Event{}
+	if err := e.Unmarshal(vs[0]); err != nil {
+		log.Fatalf("storage: cannot unmarshal event: %v", err)
+	}
+	if e.Type == storagepb.DELETE {
+		return false
+	}
+
+	ibytes := make([]byte, 8+1+8)
+	revToBytes(mainrev, s.currentRev.sub, ibytes)
 
 	event := storagepb.Event{
 		Type: storagepb.DELETE,
@@ -265,20 +266,17 @@ func (s *store) delete(key []byte, index uint64) bool {
 		log.Fatalf("storage: cannot marshal event: %v", err)
 	}
 
-	tx := s.b.BatchTx()
-	tx.Lock()
-	defer tx.Unlock()
 	tx.UnsafePut(keyBucketName, ibytes, d)
-	err = s.kvindex.Tombstone(key, index)
+	err = s.kvindex.Tombstone(key, reversion{main: mainrev, sub: s.currentRev.sub})
 	if err != nil {
 		log.Fatalf("storage: cannot tombstone an existing key (%s): %v", string(key), err)
 	}
-	s.subIndex += 1
+	s.currentRev.sub += 1
 	return true
 }
 
-func indexToBytes(index uint64, subindex uint32, bytes []byte) {
-	binary.BigEndian.PutUint64(bytes, index)
+func revToBytes(main int64, sub int64, bytes []byte) {
+	binary.BigEndian.PutUint64(bytes, uint64(main))
 	bytes[8] = '_'
-	binary.BigEndian.PutUint32(bytes[9:], subindex)
+	binary.BigEndian.PutUint64(bytes[9:], uint64(sub))
 }

storage/kvstore_test.go

@@ -16,9 +16,9 @@ func TestRange(t *testing.T) {
 
 	tests := []struct {
 		key, end []byte
-		index    int64
+		rev      int64
 
-		windex int64
+		wrev int64
 		// TODO: change this to the actual kv
 		wN int64
 	}{
@@ -41,12 +41,12 @@ func TestRange(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		kvs, index := s.Range(tt.key, tt.end, 0, tt.index)
+		kvs, rev := s.Range(tt.key, tt.end, 0, tt.rev)
 		if len(kvs) != int(tt.wN) {
 			t.Errorf("#%d: len(kvs) = %d, want %d", i, len(kvs), tt.wN)
 		}
-		if index != tt.windex {
-			t.Errorf("#%d: index = %d, wang %d", i, tt.index, tt.windex)
+		if rev != tt.wrev {
+			t.Errorf("#%d: rev = %d, want %d", i, tt.rev, tt.wrev)
 		}
 	}
 }
@@ -55,8 +55,8 @@ func TestSimpleDeleteRange(t *testing.T) {
 	tests := []struct {
 		key, end []byte
 
-		windex int64
-		wN     int64
+		wrev int64
+		wN   int64
 	}{
 		{
 			[]byte("foo"), []byte("foo1"),
@@ -83,12 +83,12 @@ func TestSimpleDeleteRange(t *testing.T) {
 		s.Put([]byte("foo1"), []byte("bar1"))
 		s.Put([]byte("foo2"), []byte("bar2"))
 
-		n, index := s.DeleteRange(tt.key, tt.end)
+		n, rev := s.DeleteRange(tt.key, tt.end)
 		if n != tt.wN {
 			t.Errorf("#%d: n = %d, want %d", i, n, tt.wN)
 		}
-		if index != tt.windex {
-			t.Errorf("#%d: index = %d, wang %d", i, index, tt.windex)
+		if rev != tt.wrev {
+			t.Errorf("#%d: rev = %d, wang %d", i, rev, tt.wrev)
 		}
 
 		os.Remove("test")
@@ -104,49 +104,49 @@ func TestRangeInSequence(t *testing.T) {
 	s.Put([]byte("foo2"), []byte("bar2"))
 
 	// remove foo
-	n, index := s.DeleteRange([]byte("foo"), nil)
-	if n != 1 || index != 4 {
-		t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 1, 4)
+	n, rev := s.DeleteRange([]byte("foo"), nil)
+	if n != 1 || rev != 4 {
+		t.Fatalf("n = %d, index = %d, want (%d, %d)", n, rev, 1, 4)
 	}
 
 	// before removal foo
-	kvs, index := s.Range([]byte("foo"), []byte("foo3"), 0, 3)
+	kvs, rev := s.Range([]byte("foo"), []byte("foo3"), 0, 3)
 	if len(kvs) != 3 {
 		t.Fatalf("len(kvs) = %d, want %d", len(kvs), 3)
 	}
 
 	// after removal foo
-	kvs, index = s.Range([]byte("foo"), []byte("foo3"), 0, 4)
+	kvs, rev = s.Range([]byte("foo"), []byte("foo3"), 0, 4)
 	if len(kvs) != 2 {
 		t.Fatalf("len(kvs) = %d, want %d", len(kvs), 2)
 	}
 
 	// remove again -> expect nothing
-	n, index = s.DeleteRange([]byte("foo"), nil)
-	if n != 0 || index != 4 {
-		t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 0, 4)
+	n, rev = s.DeleteRange([]byte("foo"), nil)
+	if n != 0 || rev != 4 {
+		t.Fatalf("n = %d, rev = %d, want (%d, %d)", n, rev, 0, 4)
 	}
 
 	// remove foo1
-	n, index = s.DeleteRange([]byte("foo"), []byte("foo2"))
-	if n != 1 || index != 5 {
-		t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 1, 5)
+	n, rev = s.DeleteRange([]byte("foo"), []byte("foo2"))
+	if n != 1 || rev != 5 {
+		t.Fatalf("n = %d, rev = %d, want (%d, %d)", n, rev, 1, 5)
 	}
 
 	// after removal foo1
-	kvs, index = s.Range([]byte("foo"), []byte("foo3"), 0, 5)
+	kvs, rev = s.Range([]byte("foo"), []byte("foo3"), 0, 5)
 	if len(kvs) != 1 {
 		t.Fatalf("len(kvs) = %d, want %d", len(kvs), 1)
 	}
 
 	// remove foo2
-	n, index = s.DeleteRange([]byte("foo2"), []byte("foo3"))
-	if n != 1 || index != 6 {
-		t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 1, 6)
+	n, rev = s.DeleteRange([]byte("foo2"), []byte("foo3"))
+	if n != 1 || rev != 6 {
+		t.Fatalf("n = %d, rev = %d, want (%d, %d)", n, rev, 1, 6)
 	}
 
 	// after removal foo2
-	kvs, index = s.Range([]byte("foo"), []byte("foo3"), 0, 6)
+	kvs, rev = s.Range([]byte("foo"), []byte("foo3"), 0, 6)
 	if len(kvs) != 0 {
 		t.Fatalf("len(kvs) = %d, want %d", len(kvs), 0)
 	}
@@ -163,15 +163,15 @@ func TestOneTnx(t *testing.T) {
 		s.TnxPut(id, []byte("foo2"), []byte("bar2"))
 
 		// remove foo
-		n, index, err := s.TnxDeleteRange(id, []byte("foo"), nil)
+		n, rev, err := s.TnxDeleteRange(id, []byte("foo"), nil)
 		if err != nil {
 			t.Fatal(err)
 		}
-		if n != 1 || index != 1 {
-			t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 1, 1)
+		if n != 1 || rev != 1 {
+			t.Fatalf("n = %d, rev = %d, want (%d, %d)", n, rev, 1, 1)
 		}
 
-		kvs, index, err := s.TnxRange(id, []byte("foo"), []byte("foo3"), 0, 0)
+		kvs, rev, err := s.TnxRange(id, []byte("foo"), []byte("foo3"), 0, 0)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -180,25 +180,25 @@ func TestOneTnx(t *testing.T) {
 		}
 
 		// remove again -> expect nothing
-		n, index, err = s.TnxDeleteRange(id, []byte("foo"), nil)
+		n, rev, err = s.TnxDeleteRange(id, []byte("foo"), nil)
 		if err != nil {
 			t.Fatal(err)
 		}
-		if n != 0 || index != 1 {
-			t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 0, 1)
+		if n != 0 || rev != 1 {
+			t.Fatalf("n = %d, rev = %d, want (%d, %d)", n, rev, 0, 1)
 		}
 
 		// remove foo1
-		n, index, err = s.TnxDeleteRange(id, []byte("foo"), []byte("foo2"))
+		n, rev, err = s.TnxDeleteRange(id, []byte("foo"), []byte("foo2"))
 		if err != nil {
 			t.Fatal(err)
 		}
-		if n != 1 || index != 1 {
-			t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 1, 1)
+		if n != 1 || rev != 1 {
+			t.Fatalf("n = %d, rev = %d, want (%d, %d)", n, rev, 1, 1)
 		}
 
 		// after removal foo1
-		kvs, index, err = s.TnxRange(id, []byte("foo"), []byte("foo3"), 0, 0)
+		kvs, rev, err = s.TnxRange(id, []byte("foo"), []byte("foo3"), 0, 0)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -207,16 +207,16 @@ func TestOneTnx(t *testing.T) {
 		}
 
 		// remove foo2
-		n, index, err = s.TnxDeleteRange(id, []byte("foo2"), []byte("foo3"))
+		n, rev, err = s.TnxDeleteRange(id, []byte("foo2"), []byte("foo3"))
 		if err != nil {
 			t.Fatal(err)
 		}
-		if n != 1 || index != 1 {
-			t.Fatalf("n = %d, index = %d, want (%d, %d)", n, index, 1, 1)
+		if n != 1 || rev != 1 {
+			t.Fatalf("n = %d, rev = %d, want (%d, %d)", n, rev, 1, 1)
 		}
 
 		// after removal foo2
-		kvs, index, err = s.TnxRange(id, []byte("foo"), []byte("foo3"), 0, 0)
+		kvs, rev, err = s.TnxRange(id, []byte("foo"), []byte("foo3"), 0, 0)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -230,12 +230,12 @@ func TestOneTnx(t *testing.T) {
 	}
 
 	// After tnx
-	kvs, index := s.Range([]byte("foo"), []byte("foo3"), 0, 1)
+	kvs, rev := s.Range([]byte("foo"), []byte("foo3"), 0, 1)
 	if len(kvs) != 0 {
 		t.Fatalf("len(kvs) = %d, want %d", len(kvs), 0)
 	}
-	if index != 1 {
-		t.Fatalf("index = %d, want %d", index, 1)
+	if rev != 1 {
+		t.Fatalf("rev = %d, want %d", rev, 1)
 	}
 }