dao: do not look up new NEP17 batch

It will fail anyway.

pkg/core/blockchain.go

@@ -946,11 +946,12 @@ func (bc *Blockchain) processNEP17Transfer(cache *dao.Cached, h util.Uint256, b
 		bs.LastUpdatedBlock = b.Index
 		balances.Trackers[id] = bs
 		transfer.Amount = *new(big.Int).Sub(&transfer.Amount, amount)
-		isBig, err := cache.AppendNEP17Transfer(fromAddr, balances.NextTransferBatch, transfer)
+		balances.NewBatch, err = cache.AppendNEP17Transfer(fromAddr,
+			balances.NextTransferBatch, balances.NewBatch, transfer)
 		if err != nil {
 			return
 		}
-		if isBig {
+		if balances.NewBatch {
 			balances.NextTransferBatch++
 		}
 		if err := cache.PutNEP17Balances(fromAddr, balances); err != nil {
@@ -968,11 +969,12 @@ func (bc *Blockchain) processNEP17Transfer(cache *dao.Cached, h util.Uint256, b
 		balances.Trackers[id] = bs
 
 		transfer.Amount = *amount
-		isBig, err := cache.AppendNEP17Transfer(toAddr, balances.NextTransferBatch, transfer)
+		balances.NewBatch, err = cache.AppendNEP17Transfer(toAddr,
+			balances.NextTransferBatch, balances.NewBatch, transfer)
 		if err != nil {
 			return
 		}
-		if isBig {
+		if balances.NewBatch {
 			balances.NextTransferBatch++
 		}
 		if err := cache.PutNEP17Balances(toAddr, balances); err != nil {

pkg/core/dao/cacheddao.go

@@ -61,10 +61,16 @@ func (cd *Cached) PutNEP17TransferLog(acc util.Uint160, index uint32, bs *state.
 }
 
 // AppendNEP17Transfer appends new transfer to a transfer event log.
-func (cd *Cached) AppendNEP17Transfer(acc util.Uint160, index uint32, tr *state.NEP17Transfer) (bool, error) {
+func (cd *Cached) AppendNEP17Transfer(acc util.Uint160, index uint32, isNew bool, tr *state.NEP17Transfer) (bool, error) {
-	lg, err := cd.GetNEP17TransferLog(acc, index)
+	var lg *state.NEP17TransferLog
-	if err != nil {
+	if isNew {
-		return false, err
+		lg = new(state.NEP17TransferLog)
+	} else {
+		var err error
+		lg, err = cd.GetNEP17TransferLog(acc, index)
+		if err != nil {
+			return false, err
+		}
 	}
 	if err := lg.Append(tr); err != nil {
 		return false, err

pkg/core/dao/dao.go

@@ -31,7 +31,7 @@ var (
 // DAO is a data access object.
 type DAO interface {
 	AppendAppExecResult(aer *state.AppExecResult, buf *io.BufBinWriter) error
-	AppendNEP17Transfer(acc util.Uint160, index uint32, tr *state.NEP17Transfer) (bool, error)
+	AppendNEP17Transfer(acc util.Uint160, index uint32, isNew bool, tr *state.NEP17Transfer) (bool, error)
 	DeleteBlock(h util.Uint256, buf *io.BufBinWriter) error
 	DeleteContractID(id int32) error
 	DeleteStorageItem(id int32, key []byte) error
@@ -205,13 +205,16 @@ func (dao *Simple) PutNEP17TransferLog(acc util.Uint160, index uint32, lg *state
 
 // AppendNEP17Transfer appends a single NEP17 transfer to a log.
 // First return value signalizes that log size has exceeded batch size.
-func (dao *Simple) AppendNEP17Transfer(acc util.Uint160, index uint32, tr *state.NEP17Transfer) (bool, error) {
+func (dao *Simple) AppendNEP17Transfer(acc util.Uint160, index uint32, isNew bool, tr *state.NEP17Transfer) (bool, error) {
-	lg, err := dao.GetNEP17TransferLog(acc, index)
+	var lg *state.NEP17TransferLog
-	if err != nil {
+	if isNew {
-		if err != storage.ErrKeyNotFound {
+		lg = new(state.NEP17TransferLog)
+	} else {
+		var err error
+		lg, err = dao.GetNEP17TransferLog(acc, index)
+		if err != nil {
 			return false, err
 		}
-		lg = new(state.NEP17TransferLog)
 	}
 	if err := lg.Append(tr); err != nil {
 		return false, err

pkg/core/state/nep17.go

@@ -50,6 +50,8 @@ type NEP17Balances struct {
 	Trackers map[int32]NEP17Tracker
 	// NextTransferBatch stores an index of the next transfer batch.
 	NextTransferBatch uint32
+	// NewBatch is true if batch with the `NextTransferBatch` index should be created.
+	NewBatch bool
 }
 
 // NewNEP17Balances returns new NEP17Balances.
@@ -62,6 +64,7 @@ func NewNEP17Balances() *NEP17Balances {
 // DecodeBinary implements io.Serializable interface.
 func (bs *NEP17Balances) DecodeBinary(r *io.BinReader) {
 	bs.NextTransferBatch = r.ReadU32LE()
+	bs.NewBatch = r.ReadBool()
 	lenBalances := r.ReadVarUint()
 	m := make(map[int32]NEP17Tracker, lenBalances)
 	for i := 0; i < int(lenBalances); i++ {
@@ -76,6 +79,7 @@ func (bs *NEP17Balances) DecodeBinary(r *io.BinReader) {
 // EncodeBinary implements io.Serializable interface.
 func (bs *NEP17Balances) EncodeBinary(w *io.BinWriter) {
 	w.WriteU32LE(bs.NextTransferBatch)
+	w.WriteBool(bs.NewBatch)
 	w.WriteVarUint(uint64(len(bs.Trackers)))
 	for k, v := range bs.Trackers {
 		w.WriteU32LE(uint32(k))