core: store statesync-related storage items under temp prefix

State jump should be an atomic operation, we can't modify contract
storage items state on-the-fly. Thus, store fresh items under temp
prefix and replase the outdated ones after state sync is completed.
Related
https://github.com/nspcc-dev/neo-go/pull/2019#discussion_r693350460.

pkg/core/blockchain.go

@@ -35,6 +35,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger"
 	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/util/slice"
 	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
 	"go.uber.org/zap"
@@ -43,7 +44,7 @@ import (
 // Tuning parameters.
 const (
 	headerBatchCount = 2000
-	version          = "0.1.2"
+	version          = "0.1.3"
 
 	defaultInitialGAS                      = 52000000_00000000
 	defaultMemPoolSize                     = 50000
@@ -451,6 +452,27 @@ func (bc *Blockchain) JumpToState(module blockchainer.StateSync) error {
 		return fmt.Errorf("can't perform MPT jump to height %d: %w", p, err)
 	}
 
+	b := bc.dao.Store.Batch()
+	bc.dao.Store.Seek([]byte{byte(storage.STStorage)}, func(k, _ []byte) {
+		// Must copy here, #1468.
+		key := slice.Copy(k)
+		b.Delete(key)
+	})
+	bc.dao.Store.Seek([]byte{byte(storage.STTempStorage)}, func(k, v []byte) {
+		// Must copy here, #1468.
+		oldKey := slice.Copy(k)
+		b.Delete(oldKey)
+		key := make([]byte, len(k))
+		key[0] = byte(storage.STStorage)
+		copy(key[1:], k[1:])
+		value := slice.Copy(v)
+		b.Put(key, value)
+	})
+	err = bc.dao.Store.PutBatch(b)
+	if err != nil {
+		return fmt.Errorf("failed to replace outdated contract storage items with the fresh ones: %w", err)
+	}
+
 	err = bc.contracts.NEO.InitializeCache(bc, bc.dao)
 	if err != nil {
 		return fmt.Errorf("can't init cache for NEO native contract: %w", err)

pkg/core/mpt/billet.go

@@ -62,9 +62,9 @@ func (b *Billet) RestoreHashNode(path []byte, node Node) error {
 	}
 	b.root = r
 
-	// If it's a leaf, then put into contract storage.
+	// If it's a leaf, then put into temporary contract storage.
 	if leaf, ok := node.(*LeafNode); ok {
-		k := append([]byte{byte(storage.STStorage)}, fromNibbles(path)...)
+		k := append([]byte{byte(storage.STTempStorage)}, fromNibbles(path)...)
 		_ = b.Store.Put(k, leaf.value)
 	}
 	return nil

pkg/core/storage/store.go

@@ -8,13 +8,18 @@ import (
 
 // KeyPrefix constants.
 const (
-	DataBlock                      KeyPrefix = 0x01
-	DataTransaction                KeyPrefix = 0x02
-	DataMPT                        KeyPrefix = 0x03
-	STAccount                      KeyPrefix = 0x40
-	STNotification                 KeyPrefix = 0x4d
-	STContractID                   KeyPrefix = 0x51
-	STStorage                      KeyPrefix = 0x70
+	DataBlock       KeyPrefix = 0x01
+	DataTransaction KeyPrefix = 0x02
+	DataMPT         KeyPrefix = 0x03
+	STAccount       KeyPrefix = 0x40
+	STNotification  KeyPrefix = 0x4d
+	STContractID    KeyPrefix = 0x51
+	STStorage       KeyPrefix = 0x70
+	// STTempStorage is used to store contract storage items during state sync process
+	// in order not to mess up the previous state which has its own items stored by
+	// STStorage prefix. Once state exchange process is completed, all items with
+	// STStorage prefix will be replaced with STTempStorage-prefixed ones.
+	STTempStorage                  KeyPrefix = 0x71
 	STNEP17Transfers               KeyPrefix = 0x72
 	STNEP17TransferInfo            KeyPrefix = 0x73
 	IXHeaderHashList               KeyPrefix = 0x80