bool IndexScanExecutor::ExecPrimaryIndexLookup() {
  PL_ASSERT(!done_);

  std::vector<ItemPointer *> tuple_location_ptrs;

  PL_ASSERT(index_->GetIndexType() == INDEX_CONSTRAINT_TYPE_PRIMARY_KEY);

  if (0 == key_column_ids_.size()) {
    index_->ScanAllKeys(tuple_location_ptrs);
  } else {
    index_->Scan(values_, key_column_ids_, expr_types_,
                 SCAN_DIRECTION_TYPE_FORWARD, tuple_location_ptrs);
  }


  if (tuple_location_ptrs.size() == 0) return false;

  auto &transaction_manager =
      concurrency::TransactionManagerFactory::GetInstance();

  std::map<oid_t, std::vector<oid_t>> visible_tuples;
  std::vector<ItemPointer> garbage_tuples;
  // for every tuple that is found in the index.
  for (auto tuple_location_ptr : tuple_location_ptrs) {
    
    ItemPointer tuple_location = *tuple_location_ptr;
    
    auto &manager = catalog::Manager::GetInstance();
    auto tile_group = manager.GetTileGroup(tuple_location.block);
    auto tile_group_header = tile_group.get()->GetHeader();

    size_t chain_length = 0;
    while (true) {

      ++chain_length;

      // if the tuple is visible.
      if (transaction_manager.IsVisible(tile_group_header,
                                        tuple_location.offset)) {

        LOG_TRACE("traverse chain length : %lu", chain_length);
        LOG_TRACE("perform read: %u, %u", tuple_location.block,
                 tuple_location.offset);

        // perform predicate evaluation.
        if (predicate_ == nullptr) {
          visible_tuples[tuple_location.block].push_back(tuple_location.offset);

          auto res = transaction_manager.PerformRead(tuple_location);
          if (!res) {
            transaction_manager.SetTransactionResult(RESULT_FAILURE);
            return res;
          }
        } else {
          expression::ContainerTuple<storage::TileGroup> tuple(
              tile_group.get(), tuple_location.offset);
          auto eval =
              predicate_->Evaluate(&tuple, nullptr, executor_context_).IsTrue();
          if (eval == true) {
            visible_tuples[tuple_location.block]
                .push_back(tuple_location.offset);

            auto res = transaction_manager.PerformRead(tuple_location);
            if (!res) {
              transaction_manager.SetTransactionResult(RESULT_FAILURE);
              return res;
            }
          }
        }
        break;
      }
      // if the tuple is not visible.
      else {
        ItemPointer old_item = tuple_location;
        cid_t old_end_cid = tile_group_header->GetEndCommitId(old_item.offset);

        tuple_location = tile_group_header->GetNextItemPointer(old_item.offset);
        // there must exist a visible version.

        // FIXME: currently, only speculative read transaction manager **may** see a null version
        // it's a potential bug
        if(tuple_location.IsNull()) {
          transaction_manager.SetTransactionResult(RESULT_FAILURE);
          // FIXME: this cause unnecessary abort when we have delete operations
          return false;
        }

        // FIXME: Is this always true? what if we have a deleted tuple? --jiexi
        PL_ASSERT(tuple_location.IsNull() == false);

        cid_t max_committed_cid = transaction_manager.GetMaxCommittedCid();

        // check whether older version is garbage.

        if (old_end_cid <= max_committed_cid) {
          PL_ASSERT(tile_group_header->GetTransactionId(old_item.offset) == INITIAL_TXN_ID ||
                      tile_group_header->GetTransactionId(old_item.offset) == INVALID_TXN_ID);

          if (tile_group_header->SetAtomicTransactionId(old_item.offset, INVALID_TXN_ID) == true) {

            // atomically swap item pointer held in the index bucket.
            AtomicUpdateItemPointer(tuple_location_ptr, tuple_location);

            // currently, let's assume only primary index exists.
            // gc::GCManagerFactory::GetInstance().RecycleTupleSlot(
            //     table_->GetOid(), old_item.block, old_item.offset,
            //     transaction_manager.GetNextCommitId());
            garbage_tuples.push_back(old_item);

            tile_group = manager.GetTileGroup(tuple_location.block);
            tile_group_header = tile_group.get()->GetHeader();
            tile_group_header->SetPrevItemPointer(tuple_location.offset, INVALID_ITEMPOINTER);

          } else {

            tile_group = manager.GetTileGroup(tuple_location.block);
            tile_group_header = tile_group.get()->GetHeader();
          }

        } else {
        tile_group = manager.GetTileGroup(tuple_location.block);
        tile_group_header = tile_group.get()->GetHeader();

        }


      }
    }
  }

  // Add all garbage tuples to GC manager
  if(garbage_tuples.size() != 0) {
    cid_t garbage_timestamp = transaction_manager.GetNextCommitId();
    for (auto garbage : garbage_tuples) {
      gc::GCManagerFactory::GetInstance().RecycleTupleSlot(
        table_->GetOid(), garbage.block, garbage.offset, garbage_timestamp);
    }
  }

  // Construct a logical tile for each block
  for (auto tuples : visible_tuples) {
    auto &manager = catalog::Manager::GetInstance();
    auto tile_group = manager.GetTileGroup(tuples.first);

    std::unique_ptr<LogicalTile> logical_tile(LogicalTileFactory::GetTile());
    // Add relevant columns to logical tile
    logical_tile->AddColumns(tile_group, full_column_ids_);
    logical_tile->AddPositionList(std::move(tuples.second));
    if (column_ids_.size() != 0) {
      logical_tile->ProjectColumns(full_column_ids_, column_ids_);
    }

    result_.push_back(logical_tile.release());
  }

  done_ = true;

  LOG_TRACE("Result tiles : %lu", result_.size());

  return true;
}
bool HybridScanExecutor::ExecPrimaryIndexLookup() {
  assert(!index_done_);

  std::vector<ItemPointer *> tuple_location_ptrs;

  assert(index_->GetIndexType() == INDEX_CONSTRAINT_TYPE_PRIMARY_KEY);

  if (0 == key_column_ids_.size()) {
    index_->ScanAllKeys(tuple_location_ptrs);
  } else {
    index_->Scan(values_, key_column_ids_, expr_types_,
                 SCAN_DIRECTION_TYPE_FORWARD, tuple_location_ptrs);
  }

  LOG_INFO("Tuple_locations.size(): %lu", tuple_location_ptrs.size());

  auto &transaction_manager =
    concurrency::TransactionManagerFactory::GetInstance();

   if (tuple_location_ptrs.size() == 0) {
    index_done_ = true;
    return false;
  }

  //std::set<oid_t> oid_ts;

  std::map<oid_t, std::vector<oid_t>> visible_tuples;
  // for every tuple that is found in the index.
  for (auto tuple_location_ptr : tuple_location_ptrs) {
    ItemPointer tuple_location = *tuple_location_ptr;

    if (type_ == planner::HYBRID &&
      tuple_location.block >= (block_threshold)) {
        item_pointers_.insert(tuple_location);
    //  oid_ts.insert(tuple_location.block);
    }

    auto &manager = catalog::Manager::GetInstance();
    auto tile_group = manager.GetTileGroup(tuple_location.block);
    auto tile_group_header = tile_group.get()->GetHeader();

    // perform transaction read
    size_t chain_length = 0;
    while (true) {

      ++chain_length;

      if (transaction_manager.IsVisible(tile_group_header,
                                        tuple_location.offset)) {
        visible_tuples[tuple_location.block].push_back(tuple_location.offset);
        auto res = transaction_manager.PerformRead(tuple_location);
        if (!res) {
          transaction_manager.SetTransactionResult(RESULT_FAILURE);
          return res;
        }
        break;
      } else {
        ItemPointer old_item = tuple_location;
        cid_t old_end_cid = tile_group_header->GetEndCommitId(old_item.offset);

        tuple_location = tile_group_header->GetNextItemPointer(old_item.offset);
        // there must exist a visible version.
        assert(tuple_location.IsNull() == false);

        cid_t max_committed_cid = transaction_manager.GetMaxCommittedCid();

        // check whether older version is garbage.
        if (old_end_cid < max_committed_cid) {
          assert(tile_group_header->GetTransactionId(old_item.offset) == INITIAL_TXN_ID ||
                 tile_group_header->GetTransactionId(old_item.offset) == INVALID_TXN_ID);

          if (tile_group_header->SetAtomicTransactionId(old_item.offset, INVALID_TXN_ID) == true) {


            // atomically swap item pointer held in the index bucket.
            AtomicUpdateItemPointer(tuple_location_ptr, tuple_location);

            // currently, let's assume only primary index exists.
            //gc::GCManagerFactory::GetInstance().RecycleTupleSlot(
            //  table_->GetOid(), old_item.block, old_item.offset,
            //  max_committed_cid);
          }
        }

        tile_group = manager.GetTileGroup(tuple_location.block);
        tile_group_header = tile_group.get()->GetHeader();
      }
    }
  }

  // Construct a logical tile for each block
  for (auto tuples : visible_tuples) {
    auto &manager = catalog::Manager::GetInstance();
    auto tile_group = manager.GetTileGroup(tuples.first);

    std::unique_ptr<LogicalTile> logical_tile(LogicalTileFactory::GetTile());
    // Add relevant columns to logical tile
    logical_tile->AddColumns(tile_group, full_column_ids_);
    logical_tile->AddPositionList(std::move(tuples.second));
    if (column_ids_.size() != 0) {
      logical_tile->ProjectColumns(full_column_ids_, column_ids_);
    }

    result_.push_back(logical_tile.release());
  }

  index_done_ = true;

  LOG_TRACE("Result tiles : %lu", result_.size());

  return true;
}
void TimestampOrderingTransactionManager::PerformUpdate(
    TransactionContext *const current_txn, const ItemPointer &location,
    const ItemPointer &new_location) {
  PL_ASSERT(current_txn->GetIsolationLevel() != IsolationLevelType::READ_ONLY);

  ItemPointer old_location = location;

  LOG_TRACE("Performing Update old tuple %u %u", old_location.block,
            old_location.offset);
  LOG_TRACE("Performing Update new tuple %u %u", new_location.block,
            new_location.offset);

  auto &manager = catalog::Manager::GetInstance();

  auto tile_group_header =
      manager.GetTileGroup(old_location.block)->GetHeader();
  auto new_tile_group_header =
      manager.GetTileGroup(new_location.block)->GetHeader();

  auto transaction_id = current_txn->GetTransactionId();
  // if we can perform update, then we must have already locked the older
  // version.
  PL_ASSERT(tile_group_header->GetTransactionId(old_location.offset) ==
            transaction_id);
  PL_ASSERT(tile_group_header->GetPrevItemPointer(old_location.offset)
                .IsNull() == true);

  // check whether the new version is empty.
  PL_ASSERT(new_tile_group_header->GetTransactionId(new_location.offset) ==
            INVALID_TXN_ID);
  PL_ASSERT(new_tile_group_header->GetBeginCommitId(new_location.offset) ==
            MAX_CID);
  PL_ASSERT(new_tile_group_header->GetEndCommitId(new_location.offset) ==
            MAX_CID);

  // if the executor doesn't call PerformUpdate after AcquireOwnership,
  // no one will possibly release the write lock acquired by this txn.

  // Set double linked list
  tile_group_header->SetPrevItemPointer(old_location.offset, new_location);

  new_tile_group_header->SetNextItemPointer(new_location.offset, old_location);

  new_tile_group_header->SetTransactionId(new_location.offset, transaction_id);

  // we should guarantee that the newer version is all set before linking the
  // newer version to older version.
  COMPILER_MEMORY_FENCE;

  InitTupleReserved(new_tile_group_header, new_location.offset);

  // we must be updating the latest version.
  // Set the header information for the new version
  ItemPointer *index_entry_ptr =
      tile_group_header->GetIndirection(old_location.offset);

  // if there's no primary index on a table, then index_entry_ptr == nullptr.
  if (index_entry_ptr != nullptr) {
    new_tile_group_header->SetIndirection(new_location.offset, index_entry_ptr);

    // Set the index header in an atomic way.
    // We do it atomically because we don't want any one to see a half-done
    // pointer.
    // In case of contention, no one can update this pointer when we are
    // updating it
    // because we are holding the write lock. This update should success in
    // its first trial.
    UNUSED_ATTRIBUTE auto res =
        AtomicUpdateItemPointer(index_entry_ptr, new_location);
    PL_ASSERT(res == true);
  }

  // Add the old tuple into the update set
  current_txn->RecordUpdate(old_location);

  // Increment table update op stats
  if (static_cast<StatsType>(settings::SettingsManager::GetInt(settings::SettingId::stats_mode)) !=
      StatsType::INVALID) {
    stats::BackendStatsContext::GetInstance()->IncrementTableUpdates(
        new_location.block);
  }
}
bool HybridScanExecutor::ExecPrimaryIndexLookup() {
  PL_ASSERT(index_done_ == false);

  const planner::HybridScanPlan &node = GetPlanNode<planner::HybridScanPlan>();
  bool acquire_owner = GetPlanNode<planner::AbstractScan>().IsForUpdate();

  auto key_column_ids_ = node.GetKeyColumnIds();
  auto expr_type_ = node.GetExprTypes();

  std::vector<ItemPointer *> tuple_location_ptrs;

  PL_ASSERT(index_->GetIndexType() == INDEX_CONSTRAINT_TYPE_PRIMARY_KEY);

  if (0 == key_column_ids_.size()) {
    LOG_TRACE("Scan all keys");
    index_->ScanAllKeys(tuple_location_ptrs);
  } else {
    LOG_TRACE("Scan");
    index_->Scan(values_,
                 key_column_ids_,
                 expr_type_,
                 SCAN_DIRECTION_TYPE_FORWARD,
                 tuple_location_ptrs,
                 &node.GetIndexPredicate().GetConjunctionList()[0]);
  }

  LOG_TRACE("Result tuple count: %lu", tuple_location_ptrs.size());

  auto &transaction_manager =
      concurrency::TransactionManagerFactory::GetInstance();

  auto current_txn = executor_context_->GetTransaction();

  if (tuple_location_ptrs.size() == 0) {
    index_done_ = true;
    return false;
  }

  std::map<oid_t, std::vector<oid_t>> visible_tuples;

  // for every tuple that is found in the index.
  for (auto tuple_location_ptr : tuple_location_ptrs) {
    ItemPointer tuple_location = *tuple_location_ptr;

    if (type_ == HYBRID_SCAN_TYPE_HYBRID &&
        tuple_location.block >= (block_threshold)) {
      item_pointers_.insert(tuple_location);
    }

    auto &manager = catalog::Manager::GetInstance();
    auto tile_group = manager.GetTileGroup(tuple_location.block);
    auto tile_group_header = tile_group.get()->GetHeader();

    // perform transaction read
    size_t chain_length = 0;
    while (true) {
      ++chain_length;

      auto visibility = transaction_manager.IsVisible(current_txn, tile_group_header, tuple_location.offset);

      if (visibility == VISIBILITY_OK) {

        visible_tuples[tuple_location.block].push_back(tuple_location.offset);
        auto res = transaction_manager.PerformRead(current_txn, tuple_location, acquire_owner);
        if (!res) {
          transaction_manager.SetTransactionResult(current_txn, RESULT_FAILURE);
          return res;
        }
        break;
      } else {
        ItemPointer old_item = tuple_location;
        cid_t old_end_cid = tile_group_header->GetEndCommitId(old_item.offset);

        tuple_location = tile_group_header->GetNextItemPointer(old_item.offset);
        // there must exist a visible version.
        assert(tuple_location.IsNull() == false);

        cid_t max_committed_cid = transaction_manager.GetMaxCommittedCid();

        // check whether older version is garbage.
        if (old_end_cid < max_committed_cid) {
          assert(tile_group_header->GetTransactionId(old_item.offset) ==
              INITIAL_TXN_ID ||
              tile_group_header->GetTransactionId(old_item.offset) ==
                  INVALID_TXN_ID);

          if (tile_group_header->SetAtomicTransactionId(
              old_item.offset, INVALID_TXN_ID) == true) {
            // atomically swap item pointer held in the index bucket.
            AtomicUpdateItemPointer(tuple_location_ptr, tuple_location);
          }
        }

        tile_group = manager.GetTileGroup(tuple_location.block);
        tile_group_header = tile_group.get()->GetHeader();
      }
    }
  }

  // Construct a logical tile for each block
  for (auto tuples : visible_tuples) {
    auto &manager = catalog::Manager::GetInstance();
    auto tile_group = manager.GetTileGroup(tuples.first);

    std::unique_ptr<LogicalTile> logical_tile(LogicalTileFactory::GetTile());

    // Add relevant columns to logical tile
    logical_tile->AddColumns(tile_group, full_column_ids_);
    logical_tile->AddPositionList(std::move(tuples.second));

    if (column_ids_.size() != 0) {
      logical_tile->ProjectColumns(full_column_ids_, column_ids_);
    }

    result_.push_back(logical_tile.release());
  }

  index_done_ = true;

  LOG_TRACE("Result tiles : %lu", result_.size());

  return true;
}