diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74a1951142..bcb3f5b70f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,8 @@ Please mark all change in change log and use the ticket from JIRA.
 - \#92 - Speed up CMake build process
 
 ## Feature
+- \#115 - Using new structure for tasktable
+
 ## Task
 
 # Milvus 0.5.0 (2019-10-21)
diff --git a/core/src/scheduler/BuildMgr.h b/core/src/scheduler/BuildMgr.h
index ee7ab38e25..805c01aafd 100644
--- a/core/src/scheduler/BuildMgr.h
+++ b/core/src/scheduler/BuildMgr.h
@@ -34,27 +34,30 @@ namespace scheduler {
 
 class BuildMgr {
  public:
-    explicit BuildMgr(int64_t numoftasks) : numoftasks_(numoftasks) {
+    explicit BuildMgr(int64_t concurrent_limit) : available_(concurrent_limit) {
     }
 
  public:
     void
     Put() {
-        ++numoftasks_;
+        std::lock_guard<std::mutex> lock(mutex_);
+        ++available_;
     }
 
-    void
-    take() {
-        --numoftasks_;
-    }
-
-    int64_t
-    numoftasks() {
-        return (int64_t)numoftasks_;
+    bool
+    Take() {
+        std::lock_guard<std::mutex> lock(mutex_);
+        if (available_ < 1) {
+            return false;
+        } else {
+            --available_;
+            return true;
+        }
     }
 
  private:
-    std::atomic_long numoftasks_;
+    std::int64_t available_;
+    std::mutex mutex_;
 };
 
 using BuildMgrPtr = std::shared_ptr<BuildMgr>;
diff --git a/core/src/scheduler/CircleQueue.h b/core/src/scheduler/CircleQueue.h
new file mode 100644
index 0000000000..5da9338ba5
--- /dev/null
+++ b/core/src/scheduler/CircleQueue.h
@@ -0,0 +1,119 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+#pragma once
+
+#include <atomic>
+#include <condition_variable>
+#include <deque>
+#include <list>
+#include <memory>
+#include <mutex>
+#include <queue>
+#include <string>
+#include <thread>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+namespace milvus {
+namespace scheduler {
+
+template <typename T>
+class CircleQueue {
+    using value_type = T;
+    using atomic_size_type = std::atomic_ullong;
+    using size_type = uint64_t;
+    using const_reference = const value_type&;
+#define MEMORY_ORDER (std::memory_order::memory_order_seq_cst)
+
+ public:
+    explicit CircleQueue(size_type cap) : data_(cap, nullptr), capacity_(cap), front_() {
+        front_.store(cap - 1, MEMORY_ORDER);
+    }
+
+    CircleQueue() = delete;
+    CircleQueue(const CircleQueue& q) = delete;
+    CircleQueue(CircleQueue&& q) = delete;
+
+ public:
+    const_reference operator[](size_type n) {
+        return data_[n % capacity_];
+    }
+
+    size_type
+    front() {
+        return front_.load(MEMORY_ORDER);
+    }
+
+    size_type
+    rear() {
+        return rear_;
+    }
+
+    size_type
+    size() {
+        return size_;
+    }
+
+    size_type
+    capacity() {
+        return capacity_;
+    }
+
+    void
+    set_front(uint64_t last_finish) {
+        if (last_finish == rear_) {
+            throw;
+        }
+        front_.store(last_finish % capacity_, MEMORY_ORDER);
+    }
+
+    void
+    put(const value_type& x) {
+        if ((rear_) % capacity_ == front_.load(MEMORY_ORDER)) {
+            throw;
+        }
+        data_[rear_] = x;
+        rear_ = ++rear_ % capacity_;
+        if (size_ < capacity_) {
+            ++size_;
+        }
+    }
+
+    void
+    put(value_type&& x) {
+        if ((rear_) % capacity_ == front_.load(MEMORY_ORDER)) {
+            throw;
+        }
+        data_[rear_] = std::move(x);
+        rear_ = ++rear_ % capacity_;
+        if (size_ < capacity_) {
+            ++size_;
+        }
+    }
+
+ private:
+    std::vector<value_type> data_;
+    size_type capacity_;
+    atomic_size_type front_;
+    size_type rear_ = 0;
+    size_type size_ = 0;
+#undef MEMORY_ORDER
+};
+
+}  // namespace scheduler
+}  // namespace milvus
diff --git a/core/src/scheduler/TaskTable.cpp b/core/src/scheduler/TaskTable.cpp
index d0e6c1c38b..e35c7cd255 100644
--- a/core/src/scheduler/TaskTable.cpp
+++ b/core/src/scheduler/TaskTable.cpp
@@ -20,6 +20,7 @@
 #include "event/TaskTableUpdatedEvent.h"
 #include "scheduler/SchedInst.h"
 #include "utils/Log.h"
+#include "utils/TimeRecorder.h"
 
 #include <ctime>
 #include <sstream>
@@ -153,7 +154,42 @@ TaskTableItem::Dump() const {
 
 std::vector<uint64_t>
 TaskTable::PickToLoad(uint64_t limit) {
-    std::lock_guard<std::mutex> lock(mutex_);
+#if 1
+    TimeRecorder rc("");
+    std::vector<uint64_t> indexes;
+    bool cross = false;
+
+    uint64_t available_begin = table_.front() + 1;
+    for (uint64_t i = 0, loaded_count = 0, pick_count = 0; i < table_.size() && pick_count < limit; ++i) {
+        auto index = available_begin + i;
+        if (not table_[index])
+            break;
+        if (index % table_.capacity() == table_.rear())
+            break;
+        if (not cross && table_[index]->IsFinish()) {
+            table_.set_front(index);
+        } else if (table_[index]->state == TaskTableItemState::LOADED) {
+            cross = true;
+            ++loaded_count;
+            if (loaded_count > 2)
+                return std::vector<uint64_t>();
+        } else if (table_[index]->state == TaskTableItemState::START) {
+            auto task = table_[index]->task;
+
+            // if task is a build index task, limit it
+            if (task->Type() == TaskType::BuildIndexTask && task->path().Current() == "cpu") {
+                if (not BuildMgrInst::GetInstance()->Take()) {
+                    continue;
+                }
+            }
+            cross = true;
+            indexes.push_back(index);
+            ++pick_count;
+        }
+    }
+    rc.ElapseFromBegin("PickToLoad ");
+    return indexes;
+#else
     size_t count = 0;
     for (uint64_t j = last_finish_ + 1; j < table_.size(); ++j) {
         if (not table_[j]) {
@@ -197,34 +233,44 @@ TaskTable::PickToLoad(uint64_t limit) {
         }
     }
     return indexes;
+#endif
 }
 
 std::vector<uint64_t>
 TaskTable::PickToExecute(uint64_t limit) {
-    std::lock_guard<std::mutex> lock(mutex_);
+    TimeRecorder rc("");
     std::vector<uint64_t> indexes;
     bool cross = false;
-    for (uint64_t i = last_finish_ + 1, count = 0; i < table_.size() && count < limit; ++i) {
-        if (not cross && table_[i]->IsFinish()) {
-            last_finish_ = i;
-        } else if (table_[i]->state == TaskTableItemState::LOADED) {
+    uint64_t available_begin = table_.front() + 1;
+    for (uint64_t i = 0, pick_count = 0; i < table_.size() && pick_count < limit; ++i) {
+        uint64_t index = available_begin + i;
+        if (not table_[index]) {
+            break;
+        }
+        if (index % table_.capacity() == table_.rear()) {
+            break;
+        }
+
+        if (not cross && table_[index]->IsFinish()) {
+            table_.set_front(index);
+        } else if (table_[index]->state == TaskTableItemState::LOADED) {
             cross = true;
-            indexes.push_back(i);
-            ++count;
+            indexes.push_back(index);
+            ++pick_count;
         }
     }
+    rc.ElapseFromBegin("PickToExecute ");
     return indexes;
 }
 
 void
 TaskTable::Put(TaskPtr task) {
-    std::lock_guard<std::mutex> lock(mutex_);
     auto item = std::make_shared<TaskTableItem>();
     item->id = id_++;
     item->task = std::move(task);
     item->state = TaskTableItemState::START;
     item->timestamp.start = get_current_timestamp();
-    table_.push_back(item);
+    table_.put(std::move(item));
     if (subscriber_) {
         subscriber_();
     }
@@ -232,14 +278,13 @@ TaskTable::Put(TaskPtr task) {
 
 void
 TaskTable::Put(std::vector<TaskPtr>& tasks) {
-    std::lock_guard<std::mutex> lock(mutex_);
     for (auto& task : tasks) {
         auto item = std::make_shared<TaskTableItem>();
         item->id = id_++;
         item->task = std::move(task);
         item->state = TaskTableItemState::START;
         item->timestamp.start = get_current_timestamp();
-        table_.push_back(item);
+        table_.put(std::move(item));
     }
     if (subscriber_) {
         subscriber_();
@@ -248,26 +293,25 @@ TaskTable::Put(std::vector<TaskPtr>& tasks) {
 
 TaskTableItemPtr
 TaskTable::Get(uint64_t index) {
-    std::lock_guard<std::mutex> lock(mutex_);
     return table_[index];
 }
 
-// void
-// TaskTable::Clear() {
-//// find first task is NOT (done or moved), erase from begin to it;
-////        auto iterator = table_.begin();
-////        while (iterator->state == TaskTableItemState::EXECUTED or
-////            iterator->state == TaskTableItemState::MOVED)
-////            iterator++;
-////        table_.erase(table_.begin(), iterator);
-//}
+size_t
+TaskTable::TaskToExecute() {
+    size_t count = 0;
+    auto begin = table_.front() + 1;
+    for (size_t i = 0; i < table_.size(); ++i) {
+        auto index = begin + i;
+        if (table_[index]->state == TaskTableItemState::LOADED) {
+            ++count;
+        }
+    }
+    return count;
+}
 
 json
 TaskTable::Dump() const {
-    json ret;
-    for (auto& item : table_) {
-        ret.push_back(item->Dump());
-    }
+    json ret{{"error.message", "not support yet."}};
     return ret;
 }
 
diff --git a/core/src/scheduler/TaskTable.h b/core/src/scheduler/TaskTable.h
index a9d00043c2..052be66890 100644
--- a/core/src/scheduler/TaskTable.h
+++ b/core/src/scheduler/TaskTable.h
@@ -25,6 +25,7 @@
 #include <utility>
 #include <vector>
 
+#include "CircleQueue.h"
 #include "event/Event.h"
 #include "interface/interfaces.h"
 #include "task/SearchTask.h"
@@ -99,7 +100,8 @@ using TaskTableItemPtr = std::shared_ptr<TaskTableItem>;
 
 class TaskTable : public interface::dumpable {
  public:
-    TaskTable() = default;
+    TaskTable() : table_(1ULL << 16ULL) {
+    }
 
     TaskTable(const TaskTable&) = delete;
     TaskTable(TaskTable&&) = delete;
@@ -128,20 +130,9 @@ class TaskTable : public interface::dumpable {
     TaskTableItemPtr
     Get(uint64_t index);
 
-    /*
-     * TODO(wxyu): BIG GC
-     * Remove sequence task which is DONE or MOVED from front;
-     * Called by ?
-     */
-    //    void
-    //    Clear();
-
-    /*
-     * Return true if task table empty, otherwise false;
-     */
-    inline bool
-    Empty() {
-        return table_.empty();
+    inline size_t
+    Capacity() {
+        return table_.capacity();
     }
 
     /*
@@ -152,22 +143,14 @@ class TaskTable : public interface::dumpable {
         return table_.size();
     }
 
+    size_t
+    TaskToExecute();
+
  public:
-    TaskTableItemPtr& operator[](uint64_t index) {
-        std::lock_guard<std::mutex> lock(mutex_);
+    const TaskTableItemPtr& operator[](uint64_t index) {
         return table_[index];
     }
 
-    std::deque<TaskTableItemPtr>::iterator
-    begin() {
-        return table_.begin();
-    }
-
-    std::deque<TaskTableItemPtr>::iterator
-    end() {
-        return table_.end();
-    }
-
  public:
     std::vector<uint64_t>
     PickToLoad(uint64_t limit);
@@ -249,8 +232,7 @@ class TaskTable : public interface::dumpable {
 
  private:
     std::uint64_t id_ = 0;
-    mutable std::mutex mutex_;
-    std::deque<TaskTableItemPtr> table_;
+    CircleQueue<TaskTableItemPtr> table_;
     std::function<void(void)> subscriber_ = nullptr;
 
     // cache last finish avoid Pick task from begin always
diff --git a/core/src/scheduler/resource/Resource.cpp b/core/src/scheduler/resource/Resource.cpp
index 1cd4cde609..2577617dab 100644
--- a/core/src/scheduler/resource/Resource.cpp
+++ b/core/src/scheduler/resource/Resource.cpp
@@ -123,12 +123,7 @@ Resource::Dump() const {
 
 uint64_t
 Resource::NumOfTaskToExec() {
-    uint64_t count = 0;
-    for (auto& task : task_table_) {
-        if (task->state == TaskTableItemState::LOADED)
-            ++count;
-    }
-    return count;
+    return task_table_.TaskToExecute();
 }
 
 TaskTableItemPtr
diff --git a/core/unittest/scheduler/test_tasktable.cpp b/core/unittest/scheduler/test_tasktable.cpp
index e717e40285..97aa1dce66 100644
--- a/core/unittest/scheduler/test_tasktable.cpp
+++ b/core/unittest/scheduler/test_tasktable.cpp
@@ -15,11 +15,10 @@
 // specific language governing permissions and limitations
 // under the License.
 
-
+#include <gtest/gtest.h>
 #include "scheduler/TaskTable.h"
 #include "scheduler/task/TestTask.h"
 #include "scheduler/tasklabel/DefaultLabel.h"
-#include <gtest/gtest.h>
 
 /************ TaskTableBaseTest ************/
 
@@ -28,15 +27,11 @@ class TaskTableItemTest : public ::testing::Test {
     void
     SetUp() override {
         std::vector<milvus::scheduler::TaskTableItemState> states{
-            milvus::scheduler::TaskTableItemState::INVALID,
-            milvus::scheduler::TaskTableItemState::START,
-            milvus::scheduler::TaskTableItemState::LOADING,
-            milvus::scheduler::TaskTableItemState::LOADED,
-            milvus::scheduler::TaskTableItemState::EXECUTING,
-            milvus::scheduler::TaskTableItemState::EXECUTED,
-            milvus::scheduler::TaskTableItemState::MOVING,
-            milvus::scheduler::TaskTableItemState::MOVED};
-        for (auto &state : states) {
+            milvus::scheduler::TaskTableItemState::INVALID,   milvus::scheduler::TaskTableItemState::START,
+            milvus::scheduler::TaskTableItemState::LOADING,   milvus::scheduler::TaskTableItemState::LOADED,
+            milvus::scheduler::TaskTableItemState::EXECUTING, milvus::scheduler::TaskTableItemState::EXECUTED,
+            milvus::scheduler::TaskTableItemState::MOVING,    milvus::scheduler::TaskTableItemState::MOVED};
+        for (auto& state : states) {
             auto item = std::make_shared<milvus::scheduler::TaskTableItem>();
             item->state = state;
             items_.emplace_back(item);
@@ -59,9 +54,9 @@ TEST_F(TaskTableItemTest, DESTRUCT) {
 }
 
 TEST_F(TaskTableItemTest, IS_FINISH) {
-    for (auto &item : items_) {
-        if (item->state == milvus::scheduler::TaskTableItemState::EXECUTED
-            || item->state == milvus::scheduler::TaskTableItemState::MOVED) {
+    for (auto& item : items_) {
+        if (item->state == milvus::scheduler::TaskTableItemState::EXECUTED ||
+            item->state == milvus::scheduler::TaskTableItemState::MOVED) {
             ASSERT_TRUE(item->IsFinish());
         } else {
             ASSERT_FALSE(item->IsFinish());
@@ -70,13 +65,13 @@ TEST_F(TaskTableItemTest, IS_FINISH) {
 }
 
 TEST_F(TaskTableItemTest, DUMP) {
-    for (auto &item : items_) {
+    for (auto& item : items_) {
         ASSERT_FALSE(item->Dump().empty());
     }
 }
 
 TEST_F(TaskTableItemTest, LOAD) {
-    for (auto &item : items_) {
+    for (auto& item : items_) {
         auto before_state = item->state;
         auto ret = item->Load();
         if (before_state == milvus::scheduler::TaskTableItemState::START) {
@@ -90,7 +85,7 @@ TEST_F(TaskTableItemTest, LOAD) {
 }
 
 TEST_F(TaskTableItemTest, LOADED) {
-    for (auto &item : items_) {
+    for (auto& item : items_) {
         auto before_state = item->state;
         auto ret = item->Loaded();
         if (before_state == milvus::scheduler::TaskTableItemState::LOADING) {
@@ -104,7 +99,7 @@ TEST_F(TaskTableItemTest, LOADED) {
 }
 
 TEST_F(TaskTableItemTest, EXECUTE) {
-    for (auto &item : items_) {
+    for (auto& item : items_) {
         auto before_state = item->state;
         auto ret = item->Execute();
         if (before_state == milvus::scheduler::TaskTableItemState::LOADED) {
@@ -118,7 +113,7 @@ TEST_F(TaskTableItemTest, EXECUTE) {
 }
 
 TEST_F(TaskTableItemTest, EXECUTED) {
-    for (auto &item : items_) {
+    for (auto& item : items_) {
         auto before_state = item->state;
         auto ret = item->Executed();
         if (before_state == milvus::scheduler::TaskTableItemState::EXECUTING) {
@@ -132,7 +127,7 @@ TEST_F(TaskTableItemTest, EXECUTED) {
 }
 
 TEST_F(TaskTableItemTest, MOVE) {
-    for (auto &item : items_) {
+    for (auto& item : items_) {
         auto before_state = item->state;
         auto ret = item->Move();
         if (before_state == milvus::scheduler::TaskTableItemState::LOADED) {
@@ -146,7 +141,7 @@ TEST_F(TaskTableItemTest, MOVE) {
 }
 
 TEST_F(TaskTableItemTest, MOVED) {
-    for (auto &item : items_) {
+    for (auto& item : items_) {
         auto before_state = item->state;
         auto ret = item->Moved();
         if (before_state == milvus::scheduler::TaskTableItemState::MOVING) {
@@ -180,9 +175,7 @@ class TaskTableBaseTest : public ::testing::Test {
 
 TEST_F(TaskTableBaseTest, SUBSCRIBER) {
     bool flag = false;
-    auto callback = [&]() {
-        flag = true;
-    };
+    auto callback = [&]() { flag = true; };
     empty_table_.RegisterSubscriber(callback);
     empty_table_.Put(task1_);
     ASSERT_TRUE(flag);
@@ -210,12 +203,6 @@ TEST_F(TaskTableBaseTest, PUT_EMPTY_BATCH) {
     empty_table_.Put(tasks);
 }
 
-TEST_F(TaskTableBaseTest, EMPTY) {
-    ASSERT_TRUE(empty_table_.Empty());
-    empty_table_.Put(task1_);
-    ASSERT_FALSE(empty_table_.Empty());
-}
-
 TEST_F(TaskTableBaseTest, SIZE) {
     ASSERT_EQ(empty_table_.Size(), 0);
     empty_table_.Put(task1_);
@@ -237,7 +224,7 @@ TEST_F(TaskTableBaseTest, PICK_TO_LOAD) {
 
     auto indexes = empty_table_.PickToLoad(1);
     ASSERT_EQ(indexes.size(), 1);
-    ASSERT_EQ(indexes[0], 2);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
 }
 
 TEST_F(TaskTableBaseTest, PICK_TO_LOAD_LIMIT) {
@@ -250,9 +237,9 @@ TEST_F(TaskTableBaseTest, PICK_TO_LOAD_LIMIT) {
 
     auto indexes = empty_table_.PickToLoad(3);
     ASSERT_EQ(indexes.size(), 3);
-    ASSERT_EQ(indexes[0], 2);
-    ASSERT_EQ(indexes[1], 3);
-    ASSERT_EQ(indexes[2], 4);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
+    ASSERT_EQ(indexes[1]% empty_table_.Capacity(), 3);
+    ASSERT_EQ(indexes[2]% empty_table_.Capacity(), 4);
 }
 
 TEST_F(TaskTableBaseTest, PICK_TO_LOAD_CACHE) {
@@ -266,14 +253,14 @@ TEST_F(TaskTableBaseTest, PICK_TO_LOAD_CACHE) {
     // first pick, non-cache
     auto indexes = empty_table_.PickToLoad(1);
     ASSERT_EQ(indexes.size(), 1);
-    ASSERT_EQ(indexes[0], 2);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
 
     // second pick, iterate from 2
     // invalid state change
     empty_table_[1]->state = milvus::scheduler::TaskTableItemState::START;
     indexes = empty_table_.PickToLoad(1);
     ASSERT_EQ(indexes.size(), 1);
-    ASSERT_EQ(indexes[0], 2);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
 }
 
 TEST_F(TaskTableBaseTest, PICK_TO_EXECUTE) {
@@ -287,7 +274,7 @@ TEST_F(TaskTableBaseTest, PICK_TO_EXECUTE) {
 
     auto indexes = empty_table_.PickToExecute(1);
     ASSERT_EQ(indexes.size(), 1);
-    ASSERT_EQ(indexes[0], 2);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
 }
 
 TEST_F(TaskTableBaseTest, PICK_TO_EXECUTE_LIMIT) {
@@ -302,8 +289,8 @@ TEST_F(TaskTableBaseTest, PICK_TO_EXECUTE_LIMIT) {
 
     auto indexes = empty_table_.PickToExecute(3);
     ASSERT_EQ(indexes.size(), 2);
-    ASSERT_EQ(indexes[0], 2);
-    ASSERT_EQ(indexes[1], 3);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
+    ASSERT_EQ(indexes[1] % empty_table_.Capacity(), 3);
 }
 
 TEST_F(TaskTableBaseTest, PICK_TO_EXECUTE_CACHE) {
@@ -318,14 +305,14 @@ TEST_F(TaskTableBaseTest, PICK_TO_EXECUTE_CACHE) {
     // first pick, non-cache
     auto indexes = empty_table_.PickToExecute(1);
     ASSERT_EQ(indexes.size(), 1);
-    ASSERT_EQ(indexes[0], 2);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
 
     // second pick, iterate from 2
     // invalid state change
     empty_table_[1]->state = milvus::scheduler::TaskTableItemState::START;
     indexes = empty_table_.PickToExecute(1);
     ASSERT_EQ(indexes.size(), 1);
-    ASSERT_EQ(indexes[0], 2);
+    ASSERT_EQ(indexes[0] % empty_table_.Capacity(), 2);
 }
 
 /************ TaskTableAdvanceTest ************/
@@ -356,8 +343,8 @@ class TaskTableAdvanceTest : public ::testing::Test {
 
 TEST_F(TaskTableAdvanceTest, LOAD) {
     std::vector<milvus::scheduler::TaskTableItemState> before_state;
-    for (auto &task : table1_) {
-        before_state.push_back(task->state);
+    for (size_t i = 0; i < table1_.Size(); ++i) {
+        before_state.push_back(table1_[i]->state);
     }
 
     for (size_t i = 0; i < table1_.Size(); ++i) {
@@ -375,8 +362,8 @@ TEST_F(TaskTableAdvanceTest, LOAD) {
 
 TEST_F(TaskTableAdvanceTest, LOADED) {
     std::vector<milvus::scheduler::TaskTableItemState> before_state;
-    for (auto &task : table1_) {
-        before_state.push_back(task->state);
+    for (size_t i = 0; i < table1_.Size(); ++i) {
+        before_state.push_back(table1_[i]->state);
     }
 
     for (size_t i = 0; i < table1_.Size(); ++i) {
@@ -394,8 +381,8 @@ TEST_F(TaskTableAdvanceTest, LOADED) {
 
 TEST_F(TaskTableAdvanceTest, EXECUTE) {
     std::vector<milvus::scheduler::TaskTableItemState> before_state;
-    for (auto &task : table1_) {
-        before_state.push_back(task->state);
+    for (size_t i = 0; i < table1_.Size(); ++i) {
+        before_state.push_back(table1_[i]->state);
     }
 
     for (size_t i = 0; i < table1_.Size(); ++i) {
@@ -413,8 +400,8 @@ TEST_F(TaskTableAdvanceTest, EXECUTE) {
 
 TEST_F(TaskTableAdvanceTest, EXECUTED) {
     std::vector<milvus::scheduler::TaskTableItemState> before_state;
-    for (auto &task : table1_) {
-        before_state.push_back(task->state);
+    for (size_t i = 0; i < table1_.Size(); ++i) {
+        before_state.push_back(table1_[i]->state);
     }
 
     for (size_t i = 0; i < table1_.Size(); ++i) {
@@ -432,8 +419,8 @@ TEST_F(TaskTableAdvanceTest, EXECUTED) {
 
 TEST_F(TaskTableAdvanceTest, MOVE) {
     std::vector<milvus::scheduler::TaskTableItemState> before_state;
-    for (auto &task : table1_) {
-        before_state.push_back(task->state);
+    for (size_t i = 0; i < table1_.Size(); ++i) {
+        before_state.push_back(table1_[i]->state);
     }
 
     for (size_t i = 0; i < table1_.Size(); ++i) {
@@ -451,8 +438,8 @@ TEST_F(TaskTableAdvanceTest, MOVE) {
 
 TEST_F(TaskTableAdvanceTest, MOVED) {
     std::vector<milvus::scheduler::TaskTableItemState> before_state;
-    for (auto &task : table1_) {
-        before_state.push_back(task->state);
+    for (size_t i = 0; i < table1_.Size(); ++i) {
+        before_state.push_back(table1_[i]->state);
     }
 
     for (size_t i = 0; i < table1_.Size(); ++i) {
@@ -467,4 +454,3 @@ TEST_F(TaskTableAdvanceTest, MOVED) {
         }
     }
 }
-