fix review comments

server/migrate_store.go

@@ -66,7 +66,7 @@ the new application db will use plain DB store types.
 			if err != nil {
 				return err
 			}
-			fmt.Printf("Multi root store is dumped at version %d \n", version)
+			fmt.Printf("Multi root store is captured at version %d \n", version)
 
 			_ = db.Close()
 			_ = newDb.Close()
@@ -80,10 +80,10 @@ the new application db will use plain DB store types.
 			if err = os.Rename(applicationMigratePath, applicationPath); err != nil {
 				return err
 			}
-			fmt.Printf("Database is replaced and the old one is backup %s\n", applicationBackupPath)
+			fmt.Printf("Application db is replaced and the old one is backup %s\n", applicationBackupPath)
 
 			_ = os.Remove(applicationMigratePath)
-			fmt.Printf("Migrate database done, please update app.toml and config.toml to use fastnode feature")
+			fmt.Printf("Migrate application db done, please update app.toml and config.toml to use fastnode feature")
 
 			return nil
 		},

store/rootmulti/store.go

@@ -142,17 +142,14 @@ func (rs *Store) MigrateStores(targetType types.StoreType, newDb dbm.DB) error {
 		return errors.New("only StoreTypeDB is supported")
 	}
 
-	batch := newDb.NewBatch()
-	defer batch.Close()
-
 	for key, store := range rs.stores {
 		switch store.GetStoreType() {
 		case types.StoreTypeIAVL:
 			rs.logger.Info("Migrating IAVL store", "store name", key.Name())
 			iterator := store.Iterator(nil, nil)
 			for ; iterator.Valid(); iterator.Next() {
 				prefixKey := append([]byte("s/k:"+key.Name()+"/"), iterator.Key()...)
-				if err := batch.Set(prefixKey, iterator.Value()); err != nil {
+				if err := newDb.SetSync(prefixKey, iterator.Value()); err != nil {
 					return err
 				}
 			}
@@ -161,9 +158,6 @@ func (rs *Store) MigrateStores(targetType types.StoreType, newDb dbm.DB) error {
 
 		}
 	}
-	if err := batch.WriteSync(); err != nil {
-		return err
-	}
 	return nil
 }