TransactionMap(Transaction transaction, String name, DataType keyType, DataType valueType) {
   this.transaction = transaction;
   ArrayType arrayType =
       new ArrayType(new DataType[] {new ObjectDataType(), new ObjectDataType(), valueType});
   MVMap.Builder<K, Object[]> builder =
       new MVMap.Builder<K, Object[]>().keyType(keyType).valueType(arrayType);
   map = transaction.store.store.openMap(name, builder);
   mapId = map.getId();
 }