storage: add Exists flag to KeyValue in batch

Set Exists flag if an item with the specified key was already
present in storage before persisting.

cli/server/dump.go

@@ -68,9 +68,14 @@ func batchToMap(index uint32, batch *storage.MemBatch) map[string]interface{} {
 			continue
 		}
 
+		op := "Added"
+		if batch.Put[i].Exists {
+			op = "Changed"
+		}
+
 		key = toNeoStorageKey(key[1:])
 		ops = append(ops, storageOp{
-			State: "Added",
+			State: op,
 			Key:   hex.EncodeToString(key),
 			Value: "00" + hex.EncodeToString(batch.Put[i].Value),
 		})
@@ -78,7 +83,7 @@ func batchToMap(index uint32, batch *storage.MemBatch) map[string]interface{} {
 
 	for i := range batch.Deleted {
 		key := batch.Deleted[i].Key
-		if len(key) == 0 || key[0] != byte(storage.STStorage) {
+		if len(key) == 0 || key[0] != byte(storage.STStorage) || !batch.Deleted[i].Exists {
 			continue
 		}
 

pkg/core/storage/memcached_store.go

@@ -14,6 +14,8 @@ type (
 	KeyValue struct {
 		Key   []byte
 		Value []byte
+
+		Exists bool
 	}
 
 	// MemBatch represents a changeset to be persisted.
@@ -54,12 +56,16 @@ func (s *MemCachedStore) GetBatch() *MemBatch {
 
 	b.Put = make([]KeyValue, 0, len(s.mem))
 	for k, v := range s.mem {
-		b.Put = append(b.Put, KeyValue{Key: []byte(k), Value: v})
+		key := []byte(k)
+		_, err := s.ps.Get(key)
+		b.Put = append(b.Put, KeyValue{Key: key, Value: v, Exists: err == nil})
 	}
 
 	b.Deleted = make([]KeyValue, 0, len(s.del))
 	for k := range s.del {
-		b.Deleted = append(b.Deleted, KeyValue{Key: []byte(k)})
+		key := []byte(k)
+		_, err := s.ps.Get(key)
+		b.Deleted = append(b.Deleted, KeyValue{Key: key, Exists: err == nil})
 	}
 
 	return &b

pkg/core/storage/memcached_store_test.go

@@ -18,7 +18,7 @@ func TestMemCachedStorePersist(t *testing.T) {
 	assert.Equal(t, 0, c)
 	// persisting one key should result in one key in ps and nothing in ts
 	assert.NoError(t, ts.Put([]byte("key"), []byte("value")))
-	checkBatch(t, ts, []KeyValue{{[]byte("key"), []byte("value")}}, nil)
+	checkBatch(t, ts, []KeyValue{{Key: []byte("key"), Value: []byte("value")}}, nil)
 	c, err = ts.Persist()
 	checkBatch(t, ts, nil, nil)
 	assert.Equal(t, nil, err)
@@ -38,8 +38,8 @@ func TestMemCachedStorePersist(t *testing.T) {
 	assert.Equal(t, ErrKeyNotFound, err)
 	assert.Equal(t, []byte(nil), v)
 	checkBatch(t, ts, []KeyValue{
-		{[]byte("key"), []byte("newvalue")},
-		{[]byte("key2"), []byte("value2")},
+		{Key: []byte("key"), Value: []byte("newvalue"), Exists: true},
+		{Key: []byte("key2"), Value: []byte("value2")},
 	}, nil)
 	// two keys should be persisted (one overwritten and one new) and
 	// available in the ps
@@ -67,7 +67,7 @@ func TestMemCachedStorePersist(t *testing.T) {
 	// test persisting deletions
 	err = ts.Delete([]byte("key"))
 	assert.Equal(t, nil, err)
-	checkBatch(t, ts, nil, []KeyValue{{Key: []byte("key")}})
+	checkBatch(t, ts, nil, []KeyValue{{Key: []byte("key"), Exists: true}})
 	c, err = ts.Persist()
 	checkBatch(t, ts, nil, nil)
 	assert.Equal(t, nil, err)