void feedInputBlocks(const relation_id rel_id, std::vector<block_id> *partially_filled_blocks) override {
   for (std::vector<block_id>::const_iterator it = partially_filled_blocks->begin();
        it != partially_filled_blocks->end();
        ++it) {
     feedInputBlock(*it, rel_id);
   }
 }
void NestedLoopsJoinOperator::feedInputBlocks(const relation_id rel_id,
                                              std::vector<block_id> *partially_filled_blocks) {
  for (std::vector<block_id>::const_iterator it = partially_filled_blocks->begin();
       it != partially_filled_blocks->end();
       ++it) {
    feedInputBlock(*it, rel_id);
  }
}