diff --git a/cpp/src/CMakeLists.txt b/cpp/src/CMakeLists.txt
index 4645ffcbe60828f8ff0695ee0eb57d98e0168021..807c16f5b301dc7a86824dd5d7d474bf5973e58d 100644
--- a/cpp/src/CMakeLists.txt
+++ b/cpp/src/CMakeLists.txt
@@ -10,10 +10,18 @@ aux_source_directory(config config_files)
 aux_source_directory(server server_files)
 aux_source_directory(utils utils_files)
 aux_source_directory(db db_files)
-aux_source_directory(db/scheduler db_scheduler_files)
 aux_source_directory(wrapper wrapper_files)
 aux_source_directory(metrics metrics_files)
 
+aux_source_directory(db/scheduler scheduler_files)
+aux_source_directory(db/scheduler/context scheduler_context_files)
+aux_source_directory(db/scheduler/task scheduler_task_files)
+set(db_scheduler_files
+        ${scheduler_files}
+        ${scheduler_context_files}
+        ${scheduler_task_files}
+        )
+
 set(license_check_files
         license/LicenseLibrary.cpp
         license/LicenseCheck.cpp
diff --git a/cpp/src/db/DBImpl.cpp b/cpp/src/db/DBImpl.cpp
index 9b541b87262bd77023a4a841533cc8533f34384f..8202c8a7db510274b2d8ab9236a4f35606e3ba9e 100644
--- a/cpp/src/db/DBImpl.cpp
+++ b/cpp/src/db/DBImpl.cpp
@@ -8,7 +8,9 @@
 #include "Log.h"
 #include "EngineFactory.h"
 #include "metrics/Metrics.h"
-#include "scheduler/SearchScheduler.h"
+#include "scheduler/TaskScheduler.h"
+#include "scheduler/context/SearchContext.h"
+#include "scheduler/context/DeleteContext.h"
 #include "utils/TimeRecorder.h"
 
 #include <assert.h>
@@ -130,48 +132,52 @@ void CalcScore(uint64_t vector_count,
 DBImpl::DBImpl(const Options& options)
     : options_(options),
       shutting_down_(false),
-      pMeta_(new meta::DBMetaImpl(options_.meta)),
-      pMemMgr_(new MemManager(pMeta_, options_)),
+      meta_ptr_(new meta::DBMetaImpl(options_.meta)),
+      mem_mgr_(new MemManager(meta_ptr_, options_)),
       compact_thread_pool_(1, 1),
       index_thread_pool_(1, 1) {
     StartTimerTasks();
 }
 
 Status DBImpl::CreateTable(meta::TableSchema& table_schema) {
-    return pMeta_->CreateTable(table_schema);
+    return meta_ptr_->CreateTable(table_schema);
 }
 
 Status DBImpl::DeleteTable(const std::string& table_id, const meta::DatesT& dates) {
-    //dates empty means delete all files of the table
-    if(dates.empty()) {
-        pMemMgr_->EraseMemVector(table_id); //not allow insert
-        pMeta_->DeleteTable(table_id); //soft delete
-    }
+    //dates partly delete files of the table but currently we don't support
+
+    mem_mgr_->EraseMemVector(table_id); //not allow insert
+    meta_ptr_->DeleteTable(table_id); //soft delete table
+
+    //scheduler will determine when to delete table files
+    TaskScheduler& scheduler = TaskScheduler::GetInstance();
+    DeleteContextPtr context = std::make_shared<DeleteContext>(table_id, meta_ptr_);
+    scheduler.Schedule(context);
 
     return Status::OK();
 }
 
 Status DBImpl::DescribeTable(meta::TableSchema& table_schema) {
-    return pMeta_->DescribeTable(table_schema);
+    return meta_ptr_->DescribeTable(table_schema);
 }
 
 Status DBImpl::HasTable(const std::string& table_id, bool& has_or_not) {
-    return pMeta_->HasTable(table_id, has_or_not);
+    return meta_ptr_->HasTable(table_id, has_or_not);
 }
 
 Status DBImpl::AllTables(std::vector<meta::TableSchema>& table_schema_array) {
-    return pMeta_->AllTables(table_schema_array);
+    return meta_ptr_->AllTables(table_schema_array);
 }
 
 Status DBImpl::GetTableRowCount(const std::string& table_id, uint64_t& row_count) {
-    return pMeta_->Count(table_id, row_count);
+    return meta_ptr_->Count(table_id, row_count);
 }
 
 Status DBImpl::InsertVectors(const std::string& table_id_,
         uint64_t n, const float* vectors, IDNumbers& vector_ids_) {
 
     auto start_time = METRICS_NOW_TIME;
-    Status status = pMemMgr_->InsertVectors(table_id_, n, vectors, vector_ids_);
+    Status status = mem_mgr_->InsertVectors(table_id_, n, vectors, vector_ids_);
     auto end_time = METRICS_NOW_TIME;
     double total_time = METRICS_MICROSECONDS(start_time,end_time);
 //    std::chrono::microseconds time_span = std::chrono::duration_cast<std::chrono::microseconds>(end_time - start_time);
@@ -203,7 +209,7 @@ Status DBImpl::Query(const std::string& table_id, uint64_t k, uint64_t nq,
 
     //get all table files from table
     meta::DatePartionedTableFilesSchema files;
-    auto status = pMeta_->FilesToSearch(table_id, dates, files);
+    auto status = meta_ptr_->FilesToSearch(table_id, dates, files);
     if (!status.ok()) { return status; }
 
     meta::TableFilesSchema file_id_array;
@@ -225,7 +231,7 @@ Status DBImpl::Query(const std::string& table_id, const std::vector<std::string>
     for (auto &id : file_ids) {
         meta::TableFileSchema table_file;
         table_file.table_id_ = id;
-        auto status = pMeta_->GetTableFile(table_file);
+        auto status = meta_ptr_->GetTableFile(table_file);
         if (!status.ok()) {
             return status;
         }
@@ -238,7 +244,7 @@ Status DBImpl::Query(const std::string& table_id, const std::vector<std::string>
 Status DBImpl::QuerySync(const std::string& table_id, uint64_t k, uint64_t nq,
                  const float* vectors, const meta::DatesT& dates, QueryResults& results) {
     meta::DatePartionedTableFilesSchema files;
-    auto status = pMeta_->FilesToSearch(table_id, dates, files);
+    auto status = meta_ptr_->FilesToSearch(table_id, dates, files);
     if (!status.ok()) { return status; }
 
     ENGINE_LOG_DEBUG << "Search DateT Size = " << files.size();
@@ -387,8 +393,8 @@ Status DBImpl::QueryAsync(const std::string& table_id, const meta::TableFilesSch
     }
 
     //step 2: put search task to scheduler
-    SearchScheduler& scheduler = SearchScheduler::GetInstance();
-    scheduler.ScheduleSearchTask(context);
+    TaskScheduler& scheduler = TaskScheduler::GetInstance();
+    scheduler.Schedule(context);
 
     context->WaitResult();
 
@@ -396,7 +402,7 @@ Status DBImpl::QueryAsync(const std::string& table_id, const meta::TableFilesSch
     auto& context_result = context->GetResult();
     meta::TableSchema table_schema;
     table_schema.table_id_ = table_id;
-    pMeta_->DescribeTable(table_schema);
+    meta_ptr_->DescribeTable(table_schema);
 
     CalcScore(context->nq(), context->vectors(), table_schema.dimension_, context_result, results);
 
@@ -460,7 +466,7 @@ void DBImpl::StartCompactionTask() {
 
     //serialize memory data
     std::vector<std::string> temp_table_ids;
-    pMemMgr_->Serialize(temp_table_ids);
+    mem_mgr_->Serialize(temp_table_ids);
     for(auto& id : temp_table_ids) {
         compact_table_ids_.insert(id);
     }
@@ -486,10 +492,10 @@ Status DBImpl::MergeFiles(const std::string& table_id, const meta::DateT& date,
     meta::TableFileSchema table_file;
     table_file.table_id_ = table_id;
     table_file.date_ = date;
-    Status status = pMeta_->CreateTableFile(table_file);
+    Status status = meta_ptr_->CreateTableFile(table_file);
 
     if (!status.ok()) {
-        LOG(INFO) << status.ToString() << std::endl;
+        ENGINE_LOG_INFO << status.ToString() << std::endl;
         return status;
     }
 
@@ -510,7 +516,7 @@ Status DBImpl::MergeFiles(const std::string& table_id, const meta::DateT& date,
 
         file_schema.file_type_ = meta::TableFileSchema::TO_DELETE;
         updated.push_back(file_schema);
-        LOG(DEBUG) << "Merging file " << file_schema.file_id_;
+        ENGINE_LOG_DEBUG << "Merging file " << file_schema.file_id_;
         index_size = index->Size();
 
         if (index_size >= options_.index_trigger_size) break;
@@ -526,8 +532,8 @@ Status DBImpl::MergeFiles(const std::string& table_id, const meta::DateT& date,
     }
     table_file.size_ = index_size;
     updated.push_back(table_file);
-    status = pMeta_->UpdateTableFiles(updated);
-    LOG(DEBUG) << "New merged file " << table_file.file_id_ <<
+    status = meta_ptr_->UpdateTableFiles(updated);
+    ENGINE_LOG_DEBUG << "New merged file " << table_file.file_id_ <<
         " of size=" << index->PhysicalSize()/(1024*1024) << " M";
 
     index->Cache();
@@ -537,7 +543,7 @@ Status DBImpl::MergeFiles(const std::string& table_id, const meta::DateT& date,
 
 Status DBImpl::BackgroundMergeFiles(const std::string& table_id) {
     meta::DatePartionedTableFilesSchema raw_files;
-    auto status = pMeta_->FilesToMerge(table_id, raw_files);
+    auto status = meta_ptr_->FilesToMerge(table_id, raw_files);
     if (!status.ok()) {
         return status;
     }
@@ -569,8 +575,8 @@ void DBImpl::BackgroundCompaction(std::set<std::string> table_ids) {
         }
     }
 
-    pMeta_->Archive();
-    pMeta_->CleanUpFilesWithTTL(1);
+    meta_ptr_->Archive();
+    meta_ptr_->CleanUpFilesWithTTL(1);
 }
 
 void DBImpl::StartBuildIndexTask() {
@@ -596,27 +602,43 @@ void DBImpl::StartBuildIndexTask() {
 }
 
 Status DBImpl::BuildIndex(const meta::TableFileSchema& file) {
-    meta::TableFileSchema table_file;
-    table_file.table_id_ = file.table_id_;
-    table_file.date_ = file.date_;
-    Status status = pMeta_->CreateTableFile(table_file);
-    if (!status.ok()) {
-        return status;
-    }
-
     ExecutionEnginePtr to_index = EngineFactory::Build(file.dimension_, file.location_, (EngineType)file.engine_type_);
     if(to_index == nullptr) {
         return Status::Error("Invalid engine type");
     }
 
     try {
+        //step 1: load index
         to_index->Load();
+
+        //step 2: create table file
+        meta::TableFileSchema table_file;
+        table_file.table_id_ = file.table_id_;
+        table_file.date_ = file.date_;
+        Status status = meta_ptr_->CreateTableFile(table_file);
+        if (!status.ok()) {
+            return status;
+        }
+
+        //step 3: build index
         auto start_time = METRICS_NOW_TIME;
         auto index = to_index->BuildIndex(table_file.location_);
         auto end_time = METRICS_NOW_TIME;
         auto total_time = METRICS_MICROSECONDS(start_time, end_time);
         server::Metrics::GetInstance().BuildIndexDurationSecondsHistogramObserve(total_time);
 
+        //step 4: if table has been deleted, dont save index file
+        bool has_table = false;
+        meta_ptr_->HasTable(file.table_id_, has_table);
+        if(!has_table) {
+            meta_ptr_->DeleteTableFiles(file.table_id_);
+            return Status::OK();
+        }
+
+        //step 5: save index file
+        index->Serialize();
+
+        //step 6: update meta
         table_file.file_type_ = meta::TableFileSchema::INDEX;
         table_file.size_ = index->Size();
 
@@ -624,13 +646,13 @@ Status DBImpl::BuildIndex(const meta::TableFileSchema& file) {
         to_remove.file_type_ = meta::TableFileSchema::TO_DELETE;
 
         meta::TableFilesSchema update_files = {to_remove, table_file};
-        pMeta_->UpdateTableFiles(update_files);
+        meta_ptr_->UpdateTableFiles(update_files);
 
-        LOG(DEBUG) << "New index file " << table_file.file_id_ << " of size "
+        ENGINE_LOG_DEBUG << "New index file " << table_file.file_id_ << " of size "
                    << index->PhysicalSize()/(1024*1024) << " M"
                    << " from file " << to_remove.file_id_;
 
-        index->Cache();
+        //index->Cache();
 
     } catch (std::exception& ex) {
         return Status::Error("Build index encounter exception", ex.what());
@@ -641,10 +663,10 @@ Status DBImpl::BuildIndex(const meta::TableFileSchema& file) {
 
 void DBImpl::BackgroundBuildIndex() {
     meta::TableFilesSchema to_index_files;
-    pMeta_->FilesToIndex(to_index_files);
+    meta_ptr_->FilesToIndex(to_index_files);
     Status status;
     for (auto& file : to_index_files) {
-        /* LOG(DEBUG) << "Buiding index for " << file.location; */
+        /* ENGINE_LOG_DEBUG << "Buiding index for " << file.location; */
         status = BuildIndex(file);
         if (!status.ok()) {
             bg_error_ = status;
@@ -655,22 +677,22 @@ void DBImpl::BackgroundBuildIndex() {
             break;
         }
     }
-    /* LOG(DEBUG) << "All Buiding index Done"; */
+    /* ENGINE_LOG_DEBUG << "All Buiding index Done"; */
 }
 
 Status DBImpl::DropAll() {
-    return pMeta_->DropAll();
+    return meta_ptr_->DropAll();
 }
 
 Status DBImpl::Size(uint64_t& result) {
-    return  pMeta_->Size(result);
+    return  meta_ptr_->Size(result);
 }
 
 DBImpl::~DBImpl() {
     shutting_down_.store(true, std::memory_order_release);
     bg_timer_thread_.join();
     std::vector<std::string> ids;
-    pMemMgr_->Serialize(ids);
+    mem_mgr_->Serialize(ids);
 }
 
 } // namespace engine
diff --git a/cpp/src/db/DBImpl.h b/cpp/src/db/DBImpl.h
index 177faeb9c111e826c993c3490d3192ce70c82df0..b4d60a27a9d518cbbb7f1c3a71ae6df5c07dd1fa 100644
--- a/cpp/src/db/DBImpl.h
+++ b/cpp/src/db/DBImpl.h
@@ -93,8 +93,8 @@ private:
 
     std::thread bg_timer_thread_;
 
-    MetaPtr pMeta_;
-    MemManagerPtr pMemMgr_;
+    MetaPtr meta_ptr_;
+    MemManagerPtr mem_mgr_;
 
     server::ThreadPool compact_thread_pool_;
     std::list<std::future<void>> compact_thread_results_;
diff --git a/cpp/src/db/DBMetaImpl.cpp b/cpp/src/db/DBMetaImpl.cpp
index 3ae34c1c2e505a752b5349ae1c25ec38eed9c42c..dbbc985067f60b7929cee418c9b5d716c31e689e 100644
--- a/cpp/src/db/DBMetaImpl.cpp
+++ b/cpp/src/db/DBMetaImpl.cpp
@@ -258,6 +258,28 @@ Status DBMetaImpl::DeleteTable(const std::string& table_id) {
     return Status::OK();
 }
 
+Status DBMetaImpl::DeleteTableFiles(const std::string& table_id) {
+    try {
+        MetricCollector metric;
+
+        //soft delete table files
+        ConnectorPtr->update_all(
+                set(
+                        c(&TableFileSchema::file_type_) = (int) TableFileSchema::TO_DELETE,
+                        c(&TableFileSchema::updated_time_) = utils::GetMicroSecTimeStamp()
+                ),
+                where(
+                        c(&TableFileSchema::table_id_) == table_id and
+                        c(&TableFileSchema::file_type_) != (int) TableFileSchema::TO_DELETE
+                ));
+
+    } catch (std::exception &e) {
+        return HandleException("Encounter exception when delete table files", e);
+    }
+
+    return Status::OK();
+}
+
 Status DBMetaImpl::DescribeTable(TableSchema &table_schema) {
     try {
         MetricCollector metric;
@@ -582,74 +604,6 @@ Status DBMetaImpl::FilesToMerge(const std::string &table_id,
     return Status::OK();
 }
 
-Status DBMetaImpl::FilesToDelete(const std::string& table_id,
-        const DatesT& partition,
-        DatePartionedTableFilesSchema& files) {
-    auto now = utils::GetMicroSecTimeStamp();
-    try {
-        if(partition.empty()) {
-            //step 1: get table files by dates
-            auto selected = ConnectorPtr->select(columns(&TableFileSchema::id_,
-                                                         &TableFileSchema::table_id_,
-                                                         &TableFileSchema::file_id_,
-                                                         &TableFileSchema::size_,
-                                                         &TableFileSchema::date_),
-                                                 where(c(&TableFileSchema::table_id_) == table_id));
-
-            //step 2: erase table files from meta
-            for (auto &file : selected) {
-                TableFileSchema table_file;
-                table_file.id_ = std::get<0>(file);
-                table_file.table_id_ = std::get<1>(file);
-                table_file.file_id_ = std::get<2>(file);
-                table_file.size_ = std::get<3>(file);
-                table_file.date_ = std::get<4>(file);
-                GetTableFilePath(table_file);
-                auto dateItr = files.find(table_file.date_);
-                if (dateItr == files.end()) {
-                    files[table_file.date_] = TableFilesSchema();
-                }
-                files[table_file.date_].push_back(table_file);
-
-                ConnectorPtr->remove<TableFileSchema>(std::get<0>(file));
-            }
-
-        } else {
-            //step 1: get all table files
-            auto selected = ConnectorPtr->select(columns(&TableFileSchema::id_,
-                                                         &TableFileSchema::table_id_,
-                                                         &TableFileSchema::file_id_,
-                                                         &TableFileSchema::size_,
-                                                         &TableFileSchema::date_),
-                                                 where(in(&TableFileSchema::date_, partition)
-                                                       and c(&TableFileSchema::table_id_) == table_id));
-
-            //step 2: erase table files from meta
-            for (auto &file : selected) {
-                TableFileSchema table_file;
-                table_file.id_ = std::get<0>(file);
-                table_file.table_id_ = std::get<1>(file);
-                table_file.file_id_ = std::get<2>(file);
-                table_file.size_ = std::get<3>(file);
-                table_file.date_ = std::get<4>(file);
-                GetTableFilePath(table_file);
-                auto dateItr = files.find(table_file.date_);
-                if (dateItr == files.end()) {
-                    files[table_file.date_] = TableFilesSchema();
-                }
-                files[table_file.date_].push_back(table_file);
-
-                ConnectorPtr->remove<TableFileSchema>(std::get<0>(file));
-            }
-        }
-
-    } catch (std::exception &e) {
-        return HandleException("Encounter exception when iterate delete files", e);
-    }
-
-    return Status::OK();
-}
-
 Status DBMetaImpl::GetTableFile(TableFileSchema &file_schema) {
 
     try {
@@ -745,40 +699,51 @@ Status DBMetaImpl::DiscardFiles(long to_discard_size) {
         return Status::OK();
     }
 
-    LOG(DEBUG) << "About to discard size=" << to_discard_size;
+    ENGINE_LOG_DEBUG << "About to discard size=" << to_discard_size;
 
     try {
-        auto selected = ConnectorPtr->select(columns(&TableFileSchema::id_,
-                                                     &TableFileSchema::size_),
-                                             where(c(&TableFileSchema::file_type_)
+        MetricCollector metric;
+
+        auto commited = ConnectorPtr->transaction([&]() mutable {
+            auto selected = ConnectorPtr->select(columns(&TableFileSchema::id_,
+                                                         &TableFileSchema::size_),
+                                                 where(c(&TableFileSchema::file_type_)
                                                        != (int) TableFileSchema::TO_DELETE),
-                                             order_by(&TableFileSchema::id_),
-                                             limit(10));
+                                                 order_by(&TableFileSchema::id_),
+                                                 limit(10));
 
-        std::vector<int> ids;
-        TableFileSchema table_file;
+            std::vector<int> ids;
+            TableFileSchema table_file;
 
-        for (auto &file : selected) {
-            if (to_discard_size <= 0) break;
-            table_file.id_ = std::get<0>(file);
-            table_file.size_ = std::get<1>(file);
-            ids.push_back(table_file.id_);
-            ENGINE_LOG_DEBUG << "Discard table_file.id=" << table_file.file_id_
-                << " table_file.size=" << table_file.size_;
-            to_discard_size -= table_file.size_;
-        }
+            for (auto &file : selected) {
+                if (to_discard_size <= 0) break;
+                table_file.id_ = std::get<0>(file);
+                table_file.size_ = std::get<1>(file);
+                ids.push_back(table_file.id_);
+                ENGINE_LOG_DEBUG << "Discard table_file.id=" << table_file.file_id_
+                                 << " table_file.size=" << table_file.size_;
+                to_discard_size -= table_file.size_;
+            }
 
-        if (ids.size() == 0) {
-            return Status::OK();
-        }
+            if (ids.size() == 0) {
+                return true;
+            }
 
-        ConnectorPtr->update_all(
-            set(
-                c(&TableFileSchema::file_type_) = (int) TableFileSchema::TO_DELETE
-            ),
-            where(
-                in(&TableFileSchema::id_, ids)
-            ));
+            ConnectorPtr->update_all(
+                    set(
+                            c(&TableFileSchema::file_type_) = (int) TableFileSchema::TO_DELETE,
+                            c(&TableFileSchema::updated_time_) = utils::GetMicroSecTimeStamp()
+                    ),
+                    where(
+                            in(&TableFileSchema::id_, ids)
+                    ));
+
+            return true;
+        });
+
+        if (!commited) {
+            return Status::DBTransactionError("Update table file error");
+        }
 
     } catch (std::exception &e) {
         return HandleException("Encounter exception when discard table file", e);
@@ -792,11 +757,21 @@ Status DBMetaImpl::UpdateTableFile(TableFileSchema &file_schema) {
     try {
         MetricCollector metric;
 
+        auto tables = ConnectorPtr->select(columns(&TableSchema::state_),
+                                           where(c(&TableSchema::table_id_) == file_schema.table_id_));
+
+        //if the table has been deleted, just mark the table file as TO_DELETE
+        //clean thread will delete the file later
+        if(tables.size() < 1 || std::get<0>(tables[0]) == (int)TableSchema::TO_DELETE) {
+            file_schema.file_type_ = TableFileSchema::TO_DELETE;
+        }
+
         ConnectorPtr->update(file_schema);
 
     } catch (std::exception &e) {
-        ENGINE_LOG_DEBUG << "table_id= " << file_schema.table_id_ << " file_id=" << file_schema.file_id_;
-        return HandleException("Encounter exception when update table file", e);
+        std::string msg = "Exception update table file: table_id = " + file_schema.table_id_
+            + " file_id = " + file_schema.file_id_;
+        return HandleException(msg, e);
     }
     return Status::OK();
 }
@@ -805,16 +780,37 @@ Status DBMetaImpl::UpdateTableFiles(TableFilesSchema &files) {
     try {
         MetricCollector metric;
 
+        std::map<std::string, bool> has_tables;
+        for (auto &file : files) {
+            if(has_tables.find(file.table_id_) != has_tables.end()) {
+                continue;
+            }
+            auto tables = ConnectorPtr->select(columns(&TableSchema::id_),
+                                               where(c(&TableSchema::table_id_) == file.table_id_
+                                                     and c(&TableSchema::state_) != (int) TableSchema::TO_DELETE));
+            if(tables.size() >= 1) {
+                has_tables[file.table_id_] = true;
+            } else {
+                has_tables[file.table_id_] = false;
+            }
+        }
+
         auto commited = ConnectorPtr->transaction([&]() mutable {
             for (auto &file : files) {
+                if(!has_tables[file.table_id_]) {
+                    file.file_type_ = TableFileSchema::TO_DELETE;
+                }
+
                 file.updated_time_ = utils::GetMicroSecTimeStamp();
                 ConnectorPtr->update(file);
             }
             return true;
         });
+
         if (!commited) {
-            return Status::DBTransactionError("Update files Error");
+            return Status::DBTransactionError("Update table files error");
         }
+
     } catch (std::exception &e) {
         return HandleException("Encounter exception when update table files", e);
     }
@@ -824,35 +820,67 @@ Status DBMetaImpl::UpdateTableFiles(TableFilesSchema &files) {
 Status DBMetaImpl::CleanUpFilesWithTTL(uint16_t seconds) {
     auto now = utils::GetMicroSecTimeStamp();
     try {
-        auto selected = ConnectorPtr->select(columns(&TableFileSchema::id_,
-                                                     &TableFileSchema::table_id_,
-                                                     &TableFileSchema::file_id_,
-                                                     &TableFileSchema::file_type_,
-                                                     &TableFileSchema::size_,
-                                                     &TableFileSchema::date_),
-                                             where(
-                                                 c(&TableFileSchema::file_type_) == (int) TableFileSchema::TO_DELETE
-                                                     and
-                                                         c(&TableFileSchema::updated_time_)
-                                                             > now - seconds * US_PS));
+        MetricCollector metric;
 
-        TableFilesSchema updated;
-        TableFileSchema table_file;
+        auto files = ConnectorPtr->select(columns(&TableFileSchema::id_,
+                                                  &TableFileSchema::table_id_,
+                                                  &TableFileSchema::file_id_,
+                                                  &TableFileSchema::date_),
+                                          where(
+                                                  c(&TableFileSchema::file_type_) ==
+                                                  (int) TableFileSchema::TO_DELETE
+                                                  and
+                                                  c(&TableFileSchema::updated_time_)
+                                                  < now - seconds * US_PS));
 
-        for (auto &file : selected) {
-            table_file.id_ = std::get<0>(file);
-            table_file.table_id_ = std::get<1>(file);
-            table_file.file_id_ = std::get<2>(file);
-            table_file.file_type_ = std::get<3>(file);
-            table_file.size_ = std::get<4>(file);
-            table_file.date_ = std::get<5>(file);
-            GetTableFilePath(table_file);
-            if (table_file.file_type_ == TableFileSchema::TO_DELETE) {
+        auto commited = ConnectorPtr->transaction([&]() mutable {
+            TableFileSchema table_file;
+            for (auto &file : files) {
+                table_file.id_ = std::get<0>(file);
+                table_file.table_id_ = std::get<1>(file);
+                table_file.file_id_ = std::get<2>(file);
+                table_file.date_ = std::get<3>(file);
+                GetTableFilePath(table_file);
+
+                ENGINE_LOG_DEBUG << "Removing deleted id =" << table_file.id_ << " location = " << table_file.location_ << std::endl;
                 boost::filesystem::remove(table_file.location_);
+                ConnectorPtr->remove<TableFileSchema>(table_file.id_);
+
+            }
+            return true;
+        });
+
+        if (!commited) {
+            return Status::DBTransactionError("Clean files error");
+        }
+
+    } catch (std::exception &e) {
+        return HandleException("Encounter exception when clean table files", e);
+    }
+
+    try {
+        MetricCollector metric;
+
+        auto tables = ConnectorPtr->select(columns(&TableSchema::id_,
+                                                   &TableSchema::table_id_),
+                                           where(c(&TableSchema::state_) == (int) TableSchema::TO_DELETE));
+
+        auto commited = ConnectorPtr->transaction([&]() mutable {
+            for (auto &table : tables) {
+                auto table_path = GetTablePath(std::get<1>(table));
+
+                ENGINE_LOG_DEBUG << "Remove table folder: " << table_path;
+                boost::filesystem::remove_all(table_path);
+                ConnectorPtr->remove<TableSchema>(std::get<0>(table));
             }
-            ConnectorPtr->remove<TableFileSchema>(table_file.id_);
-            /* LOG(DEBUG) << "Removing deleted id=" << table_file.id << " location=" << table_file.location << std::endl; */
+
+            return true;
+        });
+
+        if (!commited) {
+            return Status::DBTransactionError("Clean files error");
         }
+
     } catch (std::exception &e) {
         return HandleException("Encounter exception when clean table files", e);
     }
@@ -862,35 +890,21 @@ Status DBMetaImpl::CleanUpFilesWithTTL(uint16_t seconds) {
 
 Status DBMetaImpl::CleanUp() {
     try {
-        auto selected = ConnectorPtr->select(columns(&TableFileSchema::id_,
-                                                     &TableFileSchema::table_id_,
-                                                     &TableFileSchema::file_id_,
-                                                     &TableFileSchema::file_type_,
-                                                     &TableFileSchema::size_,
-                                                     &TableFileSchema::date_),
-                                             where(
-                                                 c(&TableFileSchema::file_type_) == (int) TableFileSchema::TO_DELETE
-                                                     or
-                                                         c(&TableFileSchema::file_type_)
-                                                             == (int) TableFileSchema::NEW));
+        auto files = ConnectorPtr->select(columns(&TableFileSchema::id_),
+                                             where(c(&TableFileSchema::file_type_) == (int) TableFileSchema::NEW));
 
-        TableFilesSchema updated;
-        TableFileSchema table_file;
-
-        for (auto &file : selected) {
-            table_file.id_ = std::get<0>(file);
-            table_file.table_id_ = std::get<1>(file);
-            table_file.file_id_ = std::get<2>(file);
-            table_file.file_type_ = std::get<3>(file);
-            table_file.size_ = std::get<4>(file);
-            table_file.date_ = std::get<5>(file);
-            GetTableFilePath(table_file);
-            if (table_file.file_type_ == TableFileSchema::TO_DELETE) {
-                boost::filesystem::remove(table_file.location_);
+        auto commited = ConnectorPtr->transaction([&]() mutable {
+            for (auto &file : files) {
+                ENGINE_LOG_DEBUG << "Remove table file type as NEW";
+                ConnectorPtr->remove<TableFileSchema>(std::get<0>(file));
             }
-            ConnectorPtr->remove<TableFileSchema>(table_file.id_);
-            /* LOG(DEBUG) << "Removing id=" << table_file.id << " location=" << table_file.location << std::endl; */
+            return true;
+        });
+
+        if (!commited) {
+            return Status::DBTransactionError("Clean files error");
         }
+
     } catch (std::exception &e) {
         return HandleException("Encounter exception when clean table file", e);
     }
@@ -903,14 +917,12 @@ Status DBMetaImpl::Count(const std::string &table_id, uint64_t &result) {
     try {
         MetricCollector metric;
 
-        auto selected = ConnectorPtr->select(columns(&TableFileSchema::size_,
-                                                     &TableFileSchema::date_),
-                                             where((c(&TableFileSchema::file_type_) == (int) TableFileSchema::RAW or
-                                                 c(&TableFileSchema::file_type_) == (int) TableFileSchema::TO_INDEX
-                                                 or
-                                                     c(&TableFileSchema::file_type_) == (int) TableFileSchema::INDEX)
-                                                       and
-                                                           c(&TableFileSchema::table_id_) == table_id));
+        auto selected = ConnectorPtr->select(columns(&TableFileSchema::size_),
+                                             where((c(&TableFileSchema::file_type_) == (int) TableFileSchema::RAW
+                                                    or
+                                                    c(&TableFileSchema::file_type_) == (int) TableFileSchema::TO_INDEX
+                                                    or c(&TableFileSchema::file_type_) == (int) TableFileSchema::INDEX)
+                                                   and c(&TableFileSchema::table_id_) == table_id));
 
         TableSchema table_schema;
         table_schema.table_id_ = table_id;
diff --git a/cpp/src/db/DBMetaImpl.h b/cpp/src/db/DBMetaImpl.h
index dcac77ded837157ac8e19cd11da645108c5928c3..21ce8d1df6a96306155843cf84b73745c7e9b1a3 100644
--- a/cpp/src/db/DBMetaImpl.h
+++ b/cpp/src/db/DBMetaImpl.h
@@ -20,11 +20,13 @@ public:
     DBMetaImpl(const DBMetaOptions& options_);
 
     virtual Status CreateTable(TableSchema& table_schema) override;
-    virtual Status DeleteTable(const std::string& table_id) override;
     virtual Status DescribeTable(TableSchema& group_info_) override;
     virtual Status HasTable(const std::string& table_id, bool& has_or_not) override;
     virtual Status AllTables(std::vector<TableSchema>& table_schema_array) override;
 
+    virtual Status DeleteTable(const std::string& table_id) override;
+    virtual Status DeleteTableFiles(const std::string& table_id) override;
+
     virtual Status CreateTableFile(TableFileSchema& file_schema) override;
     virtual Status DropPartitionsByDates(const std::string& table_id,
             const DatesT& dates) override;
@@ -42,10 +44,6 @@ public:
     virtual Status FilesToMerge(const std::string& table_id,
             DatePartionedTableFilesSchema& files) override;
 
-    virtual Status FilesToDelete(const std::string& table_id,
-                                 const DatesT& partition,
-                                 DatePartionedTableFilesSchema& files) override;
-
     virtual Status FilesToIndex(TableFilesSchema&) override;
 
     virtual Status Archive() override;
diff --git a/cpp/src/db/FaissExecutionEngine.cpp b/cpp/src/db/FaissExecutionEngine.cpp
index 467ebe31e0881a19977425a4288a3291d8b09d8f..9dfdd978c35d9d2919acb17e07f0e772be2e095e 100644
--- a/cpp/src/db/FaissExecutionEngine.cpp
+++ b/cpp/src/db/FaissExecutionEngine.cpp
@@ -4,8 +4,8 @@
  * Proprietary and confidential.
  ******************************************************************************/
 #include "FaissExecutionEngine.h"
+#include "Log.h"
 
-#include <easylogging++.h>
 #include <faiss/AutoTune.h>
 #include <faiss/MetaIndexes.h>
 #include <faiss/IndexFlat.h>
@@ -74,7 +74,7 @@ Status FaissExecutionEngine::Load() {
     if (!index) {
         index = read_index(location_);
         to_cache = true;
-        LOG(DEBUG) << "Disk io from: " << location_;
+        ENGINE_LOG_DEBUG << "Disk io from: " << location_;
     }
 
     pIndex_ = index->data();
@@ -98,6 +98,8 @@ Status FaissExecutionEngine::Merge(const std::string& location) {
     if (location == location_) {
         return Status::Error("Cannot Merge Self");
     }
+    ENGINE_LOG_DEBUG << "Merge index file: " << location << " to: " << location_;
+
     auto to_merge = zilliz::milvus::cache::CpuCacheMgr::GetInstance()->GetIndex(location);
     if (!to_merge) {
         to_merge = read_index(location);
@@ -110,6 +112,8 @@ Status FaissExecutionEngine::Merge(const std::string& location) {
 
 ExecutionEnginePtr
 FaissExecutionEngine::BuildIndex(const std::string& location) {
+    ENGINE_LOG_DEBUG << "Build index file: " << location << " from: " << location_;
+
     auto opd = std::make_shared<Operand>();
     opd->d = pIndex_->d;
     opd->index_type = build_index_type_;
@@ -122,7 +126,6 @@ FaissExecutionEngine::BuildIndex(const std::string& location) {
             from_index->id_map.data());
 
     ExecutionEnginePtr new_ee(new FaissExecutionEngine(index->data(), location, build_index_type_, raw_index_type_));
-    new_ee->Serialize();
     return new_ee;
 }
 
diff --git a/cpp/src/db/Meta.h b/cpp/src/db/Meta.h
index d8242db884537faf29b5cb05c03d61408c635378..3bd60cc7feaaeba5817629df48cb02ec753d1222 100644
--- a/cpp/src/db/Meta.h
+++ b/cpp/src/db/Meta.h
@@ -24,11 +24,13 @@ public:
     using Ptr = std::shared_ptr<Meta>;
 
     virtual Status CreateTable(TableSchema& table_schema) = 0;
-    virtual Status DeleteTable(const std::string& table_id) = 0;
     virtual Status DescribeTable(TableSchema& table_schema) = 0;
     virtual Status HasTable(const std::string& table_id, bool& has_or_not) = 0;
     virtual Status AllTables(std::vector<TableSchema>& table_schema_array) = 0;
 
+    virtual Status DeleteTable(const std::string& table_id) = 0;
+    virtual Status DeleteTableFiles(const std::string& table_id) = 0;
+
     virtual Status CreateTableFile(TableFileSchema& file_schema) = 0;
     virtual Status DropPartitionsByDates(const std::string& table_id,
             const DatesT& dates) = 0;
@@ -45,10 +47,6 @@ public:
     virtual Status FilesToMerge(const std::string& table_id,
             DatePartionedTableFilesSchema& files) = 0;
 
-    virtual Status FilesToDelete(const std::string& table_id,
-                                 const DatesT& partition,
-                                 DatePartionedTableFilesSchema& files) = 0;
-
     virtual Status Size(uint64_t& result) = 0;
 
     virtual Status Archive() = 0;
diff --git a/cpp/src/db/scheduler/ScheduleStrategy.cpp b/cpp/src/db/scheduler/ScheduleStrategy.cpp
deleted file mode 100644
index f80e01a1f4cefa6868625ca54678bc64e145c1bb..0000000000000000000000000000000000000000
--- a/cpp/src/db/scheduler/ScheduleStrategy.cpp
+++ /dev/null
@@ -1,64 +0,0 @@
-/*******************************************************************************
- * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
- * Unauthorized copying of this file, via any medium is strictly prohibited.
- * Proprietary and confidential.
- ******************************************************************************/
-
-
-#include "ScheduleStrategy.h"
-#include "cache/CpuCacheMgr.h"
-#include "utils/Error.h"
-#include "utils/Log.h"
-
-namespace zilliz {
-namespace milvus {
-namespace engine {
-
-class MemScheduleStrategy : public IScheduleStrategy {
-public:
-    bool Schedule(const SearchContextPtr &search_context, IndexLoaderQueue::LoaderQueue& loader_list) override {
-        if(search_context == nullptr) {
-            return false;
-        }
-
-        SearchContext::Id2IndexMap index_files = search_context->GetIndexMap();
-        //some index loader alread exists
-        for(auto& loader : loader_list) {
-            if(index_files.find(loader->file_->id_) != index_files.end()){
-                SERVER_LOG_INFO << "Append SearchContext to exist IndexLoaderContext";
-                index_files.erase(loader->file_->id_);
-                loader->search_contexts_.push_back(search_context);
-            }
-        }
-
-        //index_files still contains some index files, create new loader
-        for(auto& pair : index_files) {
-            SERVER_LOG_INFO << "Create new IndexLoaderContext for: " << pair.second->location_;
-            IndexLoaderContextPtr new_loader = std::make_shared<IndexLoaderContext>();
-            new_loader->search_contexts_.push_back(search_context);
-            new_loader->file_ = pair.second;
-
-            auto index  = zilliz::milvus::cache::CpuCacheMgr::GetInstance()->GetIndex(pair.second->location_);
-            if(index != nullptr) {
-                //if the index file has been in memory, increase its priority
-                loader_list.push_front(new_loader);
-            } else {
-                //index file not in memory, put it to tail
-                loader_list.push_back(new_loader);
-            }
-        }
-
-        return true;
-    }
-};
-
-
-////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
-ScheduleStrategyPtr StrategyFactory::CreateMemStrategy() {
-    ScheduleStrategyPtr strategy(new MemScheduleStrategy());
-    return strategy;
-}
-
-}
-}
-}
\ No newline at end of file
diff --git a/cpp/src/db/scheduler/SearchScheduler.cpp b/cpp/src/db/scheduler/SearchScheduler.cpp
deleted file mode 100644
index fa0dee88fb45ac7110f6ed0563f7215195027904..0000000000000000000000000000000000000000
--- a/cpp/src/db/scheduler/SearchScheduler.cpp
+++ /dev/null
@@ -1,180 +0,0 @@
-/*******************************************************************************
- * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
- * Unauthorized copying of this file, via any medium is strictly prohibited.
- * Proprietary and confidential.
- ******************************************************************************/
-
-#include "SearchScheduler.h"
-#include "IndexLoaderQueue.h"
-#include "SearchTask.h"
-#include "utils/Log.h"
-#include "utils/TimeRecorder.h"
-#include "metrics/Metrics.h"
-#include "db/EngineFactory.h"
-
-namespace zilliz {
-namespace milvus {
-namespace engine {
-
-namespace {
-void CollectFileMetrics(int file_type, size_t file_size) {
-    switch(file_type) {
-        case meta::TableFileSchema::RAW:
-        case meta::TableFileSchema::TO_INDEX: {
-            server::Metrics::GetInstance().RawFileSizeHistogramObserve(file_size);
-            server::Metrics::GetInstance().RawFileSizeTotalIncrement(file_size);
-            server::Metrics::GetInstance().RawFileSizeGaugeSet(file_size);
-            break;
-        }
-        default: {
-            server::Metrics::GetInstance().IndexFileSizeHistogramObserve(file_size);
-            server::Metrics::GetInstance().IndexFileSizeTotalIncrement(file_size);
-            server::Metrics::GetInstance().IndexFileSizeGaugeSet(file_size);
-            break;
-        }
-    }
-}
-
-void CollectDurationMetrics(int index_type, double total_time) {
-    switch(index_type) {
-        case meta::TableFileSchema::RAW: {
-            server::Metrics::GetInstance().SearchRawDataDurationSecondsHistogramObserve(total_time);
-            break;
-        }
-        case meta::TableFileSchema::TO_INDEX: {
-            server::Metrics::GetInstance().SearchRawDataDurationSecondsHistogramObserve(total_time);
-            break;
-        }
-        default: {
-            server::Metrics::GetInstance().SearchIndexDataDurationSecondsHistogramObserve(total_time);
-            break;
-        }
-    }
-}
-
-}
-
-SearchScheduler::SearchScheduler()
-    : stopped_(true) {
-    Start();
-}
-
-SearchScheduler::~SearchScheduler() {
-    Stop();
-}
-
-SearchScheduler& SearchScheduler::GetInstance() {
-    static SearchScheduler s_instance;
-    return s_instance;
-}
-
-bool
-SearchScheduler::Start() {
-    if(!stopped_) {
-        return true;
-    }
-
-    stopped_ = false;
-
-    search_queue_.SetCapacity(2);
-
-    index_load_thread_ = std::make_shared<std::thread>(&SearchScheduler::IndexLoadWorker, this);
-    search_thread_  = std::make_shared<std::thread>(&SearchScheduler::SearchWorker, this);
-
-    return true;
-}
-
-bool
-SearchScheduler::Stop() {
-    if(stopped_) {
-        return true;
-    }
-
-    if(index_load_thread_) {
-        index_load_queue_.Put(nullptr);
-        index_load_thread_->join();
-        index_load_thread_ = nullptr;
-    }
-
-    if(search_thread_) {
-        search_queue_.Put(nullptr);
-        search_thread_->join();
-        search_thread_ = nullptr;
-    }
-
-    stopped_ = true;
-
-    return true;
-}
-
-bool
-SearchScheduler::ScheduleSearchTask(SearchContextPtr& search_context) {
-    index_load_queue_.Put(search_context);
-
-    return true;
-}
-
-bool
-SearchScheduler::IndexLoadWorker() {
-    while(true) {
-        IndexLoaderContextPtr context = index_load_queue_.Take();
-        if(context == nullptr) {
-            SERVER_LOG_INFO << "Stop thread for index loading";
-            break;//exit
-        }
-
-        SERVER_LOG_INFO << "Loading index(" << context->file_->id_ << ") from location: " << context->file_->location_;
-
-        server::TimeRecorder rc("Load index");
-        //step 1: load index
-        ExecutionEnginePtr index_ptr = EngineFactory::Build(context->file_->dimension_,
-                context->file_->location_,
-                (EngineType)context->file_->engine_type_);
-        index_ptr->Load();
-
-        rc.Record("load index file to memory");
-
-        size_t file_size = index_ptr->PhysicalSize();
-        LOG(DEBUG) << "Index file type " << context->file_->file_type_ << " Of Size: "
-                   << file_size/(1024*1024) << " M";
-
-        CollectFileMetrics(context->file_->file_type_, file_size);
-
-        //step 2: put search task into another queue
-        SearchTaskPtr task_ptr = std::make_shared<SearchTask>();
-        task_ptr->index_id_ = context->file_->id_;
-        task_ptr->index_type_ = context->file_->file_type_;
-        task_ptr->index_engine_ = index_ptr;
-        task_ptr->search_contexts_.swap(context->search_contexts_);
-        search_queue_.Put(task_ptr);
-    }
-
-    return true;
-}
-
-bool
-SearchScheduler::SearchWorker() {
-    while(true) {
-        SearchTaskPtr task_ptr = search_queue_.Take();
-        if(task_ptr == nullptr) {
-            SERVER_LOG_INFO << "Stop thread for searching";
-            break;//exit
-        }
-
-        SERVER_LOG_INFO << "Searching in index(" << task_ptr->index_id_<< ") with "
-            << task_ptr->search_contexts_.size() << " tasks";
-
-        //do search
-        auto start_time = METRICS_NOW_TIME;
-        task_ptr->DoSearch();
-        auto end_time = METRICS_NOW_TIME;
-        auto total_time = METRICS_MICROSECONDS(start_time, end_time);
-        CollectDurationMetrics(task_ptr->index_type_, total_time);
-    }
-
-    return true;
-}
-
-}
-}
-}
\ No newline at end of file
diff --git a/cpp/src/db/scheduler/SearchScheduler.h b/cpp/src/db/scheduler/SearchScheduler.h
deleted file mode 100644
index 673d759056d64e867b175b5fd544939b8a74f170..0000000000000000000000000000000000000000
--- a/cpp/src/db/scheduler/SearchScheduler.h
+++ /dev/null
@@ -1,48 +0,0 @@
-/*******************************************************************************
- * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
- * Unauthorized copying of this file, via any medium is strictly prohibited.
- * Proprietary and confidential.
- ******************************************************************************/
-#pragma once
-
-#include "SearchContext.h"
-#include "IndexLoaderQueue.h"
-#include "SearchTask.h"
-
-namespace zilliz {
-namespace milvus {
-namespace engine {
-
-class SearchScheduler {
-private:
-    SearchScheduler();
-    virtual ~SearchScheduler();
-
-public:
-    static SearchScheduler& GetInstance();
-
-    bool ScheduleSearchTask(SearchContextPtr& search_context);
-
-private:
-    bool Start();
-    bool Stop();
-
-    bool IndexLoadWorker();
-    bool SearchWorker();
-
-private:
-    std::shared_ptr<std::thread> index_load_thread_;
-    std::shared_ptr<std::thread> search_thread_;
-
-    IndexLoaderQueue index_load_queue_;
-
-    using SearchTaskQueue = server::BlockingQueue<SearchTaskPtr>;
-    SearchTaskQueue search_queue_;
-
-    bool stopped_ = true;
-};
-
-
-}
-}
-}
diff --git a/cpp/src/db/scheduler/IndexLoaderQueue.cpp b/cpp/src/db/scheduler/TaskDispatchQueue.cpp
similarity index 76%
rename from cpp/src/db/scheduler/IndexLoaderQueue.cpp
rename to cpp/src/db/scheduler/TaskDispatchQueue.cpp
index 2522815520ccc512f74d86118eccc54f7fe0da95..2ce0e933b46ea3e106f1d319e7254e7d905edc74 100644
--- a/cpp/src/db/scheduler/IndexLoaderQueue.cpp
+++ b/cpp/src/db/scheduler/TaskDispatchQueue.cpp
@@ -4,8 +4,8 @@
  * Proprietary and confidential.
  ******************************************************************************/
 
-#include "IndexLoaderQueue.h"
-#include "ScheduleStrategy.h"
+#include "TaskDispatchQueue.h"
+#include "TaskDispatchStrategy.h"
 #include "utils/Error.h"
 #include "utils/Log.h"
 
@@ -14,12 +14,12 @@ namespace milvus {
 namespace engine {
 
 void
-IndexLoaderQueue::Put(const SearchContextPtr &search_context) {
+TaskDispatchQueue::Put(const ScheduleContextPtr &context) {
     std::unique_lock <std::mutex> lock(mtx);
     full_.wait(lock, [this] { return (queue_.size() < capacity_); });
 
-    if(search_context == nullptr) {
-        queue_.push_back(nullptr);
+    if(context == nullptr) {
+        queue_.push_front(nullptr);
         empty_.notify_all();
         return;
     }
@@ -32,14 +32,13 @@ IndexLoaderQueue::Put(const SearchContextPtr &search_context) {
         throw server::ServerException(server::SERVER_BLOCKING_QUEUE_EMPTY, error_msg);
     }
 
-    ScheduleStrategyPtr strategy = StrategyFactory::CreateMemStrategy();
-    strategy->Schedule(search_context, queue_);
+    TaskDispatchStrategy::Schedule(context, queue_);
 
     empty_.notify_all();
 }
 
-IndexLoaderContextPtr
-IndexLoaderQueue::Take() {
+ScheduleTaskPtr
+TaskDispatchQueue::Take() {
     std::unique_lock <std::mutex> lock(mtx);
     empty_.wait(lock, [this] { return !queue_.empty(); });
 
@@ -49,20 +48,20 @@ IndexLoaderQueue::Take() {
         throw server::ServerException(server::SERVER_BLOCKING_QUEUE_EMPTY, error_msg);
     }
 
-    IndexLoaderContextPtr front(queue_.front());
+    ScheduleTaskPtr front(queue_.front());
     queue_.pop_front();
     full_.notify_all();
     return front;
 }
 
 size_t
-IndexLoaderQueue::Size() {
+TaskDispatchQueue::Size() {
     std::lock_guard <std::mutex> lock(mtx);
     return queue_.size();
 }
 
-IndexLoaderContextPtr
-IndexLoaderQueue::Front() {
+ScheduleTaskPtr
+TaskDispatchQueue::Front() {
     std::unique_lock <std::mutex> lock(mtx);
     empty_.wait(lock, [this] { return !queue_.empty(); });
     if (queue_.empty()) {
@@ -70,12 +69,12 @@ IndexLoaderQueue::Front() {
         SERVER_LOG_ERROR << error_msg;
         throw server::ServerException(server::SERVER_BLOCKING_QUEUE_EMPTY, error_msg);
     }
-    IndexLoaderContextPtr front(queue_.front());
+    ScheduleTaskPtr front(queue_.front());
     return front;
 }
 
-IndexLoaderContextPtr
-IndexLoaderQueue::Back() {
+ScheduleTaskPtr
+TaskDispatchQueue::Back() {
     std::unique_lock <std::mutex> lock(mtx);
     empty_.wait(lock, [this] { return !queue_.empty(); });
 
@@ -85,18 +84,18 @@ IndexLoaderQueue::Back() {
         throw server::ServerException(server::SERVER_BLOCKING_QUEUE_EMPTY, error_msg);
     }
 
-    IndexLoaderContextPtr back(queue_.back());
+    ScheduleTaskPtr back(queue_.back());
     return back;
 }
 
 bool
-IndexLoaderQueue::Empty() {
+TaskDispatchQueue::Empty() {
     std::unique_lock <std::mutex> lock(mtx);
     return queue_.empty();
 }
 
 void
-IndexLoaderQueue::SetCapacity(const size_t capacity) {
+TaskDispatchQueue::SetCapacity(const size_t capacity) {
     capacity_ = (capacity > 0 ? capacity : capacity_);
 }
 
diff --git a/cpp/src/db/scheduler/IndexLoaderQueue.h b/cpp/src/db/scheduler/TaskDispatchQueue.h
similarity index 53%
rename from cpp/src/db/scheduler/IndexLoaderQueue.h
rename to cpp/src/db/scheduler/TaskDispatchQueue.h
index 4f6dcfcd67c50bf4c2bdabc5de14925e5d4eb65e..435be4f5972e88fa0c312530cf6b663134768d51 100644
--- a/cpp/src/db/scheduler/IndexLoaderQueue.h
+++ b/cpp/src/db/scheduler/TaskDispatchQueue.h
@@ -5,7 +5,8 @@
  ******************************************************************************/
 #pragma once
 
-#include "SearchContext.h"
+#include "context/IScheduleContext.h"
+#include "task/IScheduleTask.h"
 
 #include <condition_variable>
 #include <iostream>
@@ -17,31 +18,23 @@ namespace zilliz {
 namespace milvus {
 namespace engine {
 
-
-class IndexLoaderContext {
-public:
-    TableFileSchemaPtr file_;
-    std::vector<SearchContextPtr> search_contexts_;
-};
-using IndexLoaderContextPtr = std::shared_ptr<IndexLoaderContext>;
-
-class IndexLoaderQueue {
+class TaskDispatchQueue {
 public:
-    IndexLoaderQueue() : mtx(), full_(), empty_() {}
+    TaskDispatchQueue() : mtx(), full_(), empty_() {}
 
-    IndexLoaderQueue(const IndexLoaderQueue &rhs) = delete;
+    TaskDispatchQueue(const TaskDispatchQueue &rhs) = delete;
 
-    IndexLoaderQueue &operator=(const IndexLoaderQueue &rhs) = delete;
+    TaskDispatchQueue &operator=(const TaskDispatchQueue &rhs) = delete;
 
-    using LoaderQueue = std::list<IndexLoaderContextPtr>;
+    using TaskList = std::list<ScheduleTaskPtr>;
 
-    void Put(const SearchContextPtr &search_context);
+    void Put(const ScheduleContextPtr &context);
 
-    IndexLoaderContextPtr Take();
+    ScheduleTaskPtr Take();
 
-    IndexLoaderContextPtr Front();
+    ScheduleTaskPtr Front();
 
-    IndexLoaderContextPtr Back();
+    ScheduleTaskPtr Back();
 
     size_t Size();
 
@@ -54,7 +47,7 @@ private:
     std::condition_variable full_;
     std::condition_variable empty_;
 
-    LoaderQueue queue_;
+    TaskList queue_;
     size_t capacity_ = 1000000;
 };
 
diff --git a/cpp/src/db/scheduler/TaskDispatchStrategy.cpp b/cpp/src/db/scheduler/TaskDispatchStrategy.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..7200f2584ff68177940240c8decbad307599d1c2
--- /dev/null
+++ b/cpp/src/db/scheduler/TaskDispatchStrategy.cpp
@@ -0,0 +1,122 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+#include "TaskDispatchStrategy.h"
+#include "context/SearchContext.h"
+#include "context/DeleteContext.h"
+#include "task/IndexLoadTask.h"
+#include "task/DeleteTask.h"
+#include "cache/CpuCacheMgr.h"
+#include "utils/Error.h"
+#include "db/Log.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+class ReuseCacheIndexStrategy {
+public:
+    bool Schedule(const SearchContextPtr &context, std::list<ScheduleTaskPtr>& task_list) {
+        if(context == nullptr) {
+            return false;
+        }
+
+        SearchContext::Id2IndexMap index_files = context->GetIndexMap();
+        //some index loader alread exists
+        for(auto& task : task_list) {
+            if(task->type() != ScheduleTaskType::kIndexLoad) {
+                continue;
+            }
+
+            IndexLoadTaskPtr loader = std::static_pointer_cast<IndexLoadTask>(task);
+            if(index_files.find(loader->file_->id_) != index_files.end()){
+                ENGINE_LOG_INFO << "Append SearchContext to exist IndexLoaderContext";
+                index_files.erase(loader->file_->id_);
+                loader->search_contexts_.push_back(context);
+            }
+        }
+
+        //index_files still contains some index files, create new loader
+        for(auto& pair : index_files) {
+            ENGINE_LOG_INFO << "Create new IndexLoaderContext for: " << pair.second->location_;
+            IndexLoadTaskPtr new_loader = std::make_shared<IndexLoadTask>();
+            new_loader->search_contexts_.push_back(context);
+            new_loader->file_ = pair.second;
+
+            auto index  = zilliz::milvus::cache::CpuCacheMgr::GetInstance()->GetIndex(pair.second->location_);
+            if(index != nullptr) {
+                //if the index file has been in memory, increase its priority
+                task_list.push_front(new_loader);
+            } else {
+                //index file not in memory, put it to tail
+                task_list.push_back(new_loader);
+            }
+        }
+
+        return true;
+    }
+};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+class DeleteTableStrategy {
+public:
+    bool Schedule(const DeleteContextPtr &context, std::list<ScheduleTaskPtr> &task_list) {
+        if (context == nullptr) {
+            return false;
+        }
+
+        DeleteTaskPtr delete_task = std::make_shared<DeleteTask>(context);
+        if(task_list.empty()) {
+            task_list.push_back(delete_task);
+            return true;
+        }
+
+        std::string table_id = context->table_id();
+        for(auto iter = task_list.begin(); iter != task_list.end(); ++iter) {
+            if((*iter)->type() != ScheduleTaskType::kIndexLoad) {
+                continue;
+            }
+
+            //put delete task to proper position
+            IndexLoadTaskPtr loader = std::static_pointer_cast<IndexLoadTask>(*iter);
+            if(loader->file_->table_id_ == table_id) {
+
+                task_list.insert(++iter, delete_task);
+                break;
+            }
+        }
+
+        return true;
+    }
+};
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+bool TaskDispatchStrategy::Schedule(const ScheduleContextPtr &context_ptr,
+                                    std::list<zilliz::milvus::engine::ScheduleTaskPtr> &task_list) {
+    if(context_ptr == nullptr) {
+        return false;
+    }
+
+    switch(context_ptr->type()) {
+        case ScheduleContextType::kSearch: {
+            SearchContextPtr search_context = std::static_pointer_cast<SearchContext>(context_ptr);
+            ReuseCacheIndexStrategy strategy;
+            return strategy.Schedule(search_context, task_list);
+        }
+        case ScheduleContextType::kDelete: {
+            DeleteContextPtr delete_context = std::static_pointer_cast<DeleteContext>(context_ptr);
+            DeleteTableStrategy strategy;
+            return strategy.Schedule(delete_context, task_list);
+        }
+        default:
+            ENGINE_LOG_ERROR << "Invalid schedule task type";
+            return false;
+    }
+}
+
+}
+}
+}
\ No newline at end of file
diff --git a/cpp/src/db/scheduler/ScheduleStrategy.h b/cpp/src/db/scheduler/TaskDispatchStrategy.h
similarity index 66%
rename from cpp/src/db/scheduler/ScheduleStrategy.h
rename to cpp/src/db/scheduler/TaskDispatchStrategy.h
index 1fc0493e415e20f7ed70a3eb5afd87a2cee55f5e..d835e3ce86277acfdca63fa6375612d28ef0ddfe 100644
--- a/cpp/src/db/scheduler/ScheduleStrategy.h
+++ b/cpp/src/db/scheduler/TaskDispatchStrategy.h
@@ -5,18 +5,18 @@
  ******************************************************************************/
 #pragma once
 
-#include "IScheduleStrategy.h"
+#include "context/IScheduleContext.h"
+#include "task/IScheduleTask.h"
+
+#include <list>
 
 namespace zilliz {
 namespace milvus {
 namespace engine {
 
-class StrategyFactory {
-private:
-    StrategyFactory() {}
-
+class TaskDispatchStrategy {
 public:
-    static ScheduleStrategyPtr CreateMemStrategy();
+    static bool Schedule(const ScheduleContextPtr &context_ptr, std::list<ScheduleTaskPtr>& task_list);
 };
 
 }
diff --git a/cpp/src/db/scheduler/TaskScheduler.cpp b/cpp/src/db/scheduler/TaskScheduler.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..04d6762aaeddc6045186b431f2781310aa3b8227
--- /dev/null
+++ b/cpp/src/db/scheduler/TaskScheduler.cpp
@@ -0,0 +1,117 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+
+#include "TaskScheduler.h"
+#include "TaskDispatchQueue.h"
+#include "utils/Log.h"
+#include "utils/TimeRecorder.h"
+#include "db/EngineFactory.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+TaskScheduler::TaskScheduler()
+    : stopped_(true) {
+    Start();
+}
+
+TaskScheduler::~TaskScheduler() {
+    Stop();
+}
+
+TaskScheduler& TaskScheduler::GetInstance() {
+    static TaskScheduler s_instance;
+    return s_instance;
+}
+
+bool
+TaskScheduler::Start() {
+    if(!stopped_) {
+        return true;
+    }
+
+    stopped_ = false;
+
+    task_queue_.SetCapacity(2);
+
+    task_dispatch_thread_ = std::make_shared<std::thread>(&TaskScheduler::TaskDispatchWorker, this);
+    task_thread_  = std::make_shared<std::thread>(&TaskScheduler::TaskWorker, this);
+
+    return true;
+}
+
+bool
+TaskScheduler::Stop() {
+    if(stopped_) {
+        return true;
+    }
+
+    if(task_dispatch_thread_) {
+        task_dispatch_queue_.Put(nullptr);
+        task_dispatch_thread_->join();
+        task_dispatch_thread_ = nullptr;
+    }
+
+    if(task_thread_) {
+        task_queue_.Put(nullptr);
+        task_thread_->join();
+        task_thread_ = nullptr;
+    }
+
+    stopped_ = true;
+
+    return true;
+}
+
+bool
+TaskScheduler::Schedule(ScheduleContextPtr context) {
+    task_dispatch_queue_.Put(context);
+
+    return true;
+}
+
+bool
+TaskScheduler::TaskDispatchWorker() {
+    while(true) {
+        ScheduleTaskPtr task_ptr = task_dispatch_queue_.Take();
+        if(task_ptr == nullptr) {
+            SERVER_LOG_INFO << "Stop db task dispatch thread";
+            break;//exit
+        }
+
+        //execute task
+        ScheduleTaskPtr next_task = task_ptr->Execute();
+        if(next_task != nullptr) {
+            task_queue_.Put(next_task);
+        }
+    }
+
+    return true;
+}
+
+bool
+TaskScheduler::TaskWorker() {
+    while(true) {
+        ScheduleTaskPtr task_ptr = task_queue_.Take();
+        if(task_ptr == nullptr) {
+            SERVER_LOG_INFO << "Stop db task thread";
+            break;//exit
+        }
+
+        //execute task
+        ScheduleTaskPtr next_task = task_ptr->Execute();
+        if(next_task != nullptr) {
+            task_queue_.Put(next_task);
+        }
+    }
+
+    return true;
+}
+
+}
+}
+}
\ No newline at end of file
diff --git a/cpp/src/db/scheduler/TaskScheduler.h b/cpp/src/db/scheduler/TaskScheduler.h
new file mode 100644
index 0000000000000000000000000000000000000000..d03fb858ac5dea26db41b03c5666945aa7f0c761
--- /dev/null
+++ b/cpp/src/db/scheduler/TaskScheduler.h
@@ -0,0 +1,49 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+#pragma once
+
+#include "context/IScheduleContext.h"
+#include "task/IScheduleTask.h"
+#include "TaskDispatchQueue.h"
+#include "utils/BlockingQueue.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+class TaskScheduler {
+private:
+    TaskScheduler();
+    virtual ~TaskScheduler();
+
+public:
+    static TaskScheduler& GetInstance();
+
+    bool Schedule(ScheduleContextPtr context);
+
+private:
+    bool Start();
+    bool Stop();
+
+    bool TaskDispatchWorker();
+    bool TaskWorker();
+
+private:
+    std::shared_ptr<std::thread> task_dispatch_thread_;
+    std::shared_ptr<std::thread> task_thread_;
+
+    TaskDispatchQueue task_dispatch_queue_;
+
+    using TaskQueue = server::BlockingQueue<ScheduleTaskPtr>;
+    TaskQueue task_queue_;
+
+    bool stopped_ = true;
+};
+
+
+}
+}
+}
diff --git a/cpp/src/db/scheduler/context/DeleteContext.cpp b/cpp/src/db/scheduler/context/DeleteContext.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..bffeb9a134051886f291ce45a97dc231740b1120
--- /dev/null
+++ b/cpp/src/db/scheduler/context/DeleteContext.cpp
@@ -0,0 +1,22 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+
+#include "DeleteContext.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+DeleteContext::DeleteContext(const std::string& table_id, meta::Meta::Ptr& meta_ptr)
+    : IScheduleContext(ScheduleContextType::kDelete),
+      table_id_(table_id),
+      meta_ptr_(meta_ptr) {
+
+}
+
+}
+}
+}
\ No newline at end of file
diff --git a/cpp/src/db/scheduler/context/DeleteContext.h b/cpp/src/db/scheduler/context/DeleteContext.h
new file mode 100644
index 0000000000000000000000000000000000000000..b909ecb69ea36ee98f0214ad822937235dee466e
--- /dev/null
+++ b/cpp/src/db/scheduler/context/DeleteContext.h
@@ -0,0 +1,31 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+#pragma once
+
+#include "IScheduleContext.h"
+#include "db/Meta.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+class DeleteContext : public IScheduleContext {
+public:
+    DeleteContext(const std::string& table_id, meta::Meta::Ptr& meta_ptr);
+
+    std::string table_id() const { return table_id_; }
+    meta::Meta::Ptr meta() const { return meta_ptr_; }
+
+private:
+    std::string table_id_;
+    meta::Meta::Ptr meta_ptr_;
+};
+
+using DeleteContextPtr = std::shared_ptr<DeleteContext>;
+
+}
+}
+}
diff --git a/cpp/src/db/scheduler/context/IScheduleContext.h b/cpp/src/db/scheduler/context/IScheduleContext.h
new file mode 100644
index 0000000000000000000000000000000000000000..6ae56e364e4b046faa05d52a99d28cb0e85baf2b
--- /dev/null
+++ b/cpp/src/db/scheduler/context/IScheduleContext.h
@@ -0,0 +1,38 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+#pragma once
+
+#include <memory>
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+enum class ScheduleContextType {
+    kUnknown = 0,
+    kSearch,
+    kDelete,
+};
+
+class IScheduleContext {
+public:
+    IScheduleContext(ScheduleContextType type)
+    : type_(type) {
+    }
+
+    virtual ~IScheduleContext() = default;
+
+    ScheduleContextType type() const { return type_; }
+
+protected:
+    ScheduleContextType type_;
+};
+
+using ScheduleContextPtr = std::shared_ptr<IScheduleContext>;
+
+}
+}
+}
diff --git a/cpp/src/db/scheduler/SearchContext.cpp b/cpp/src/db/scheduler/context/SearchContext.cpp
similarity index 95%
rename from cpp/src/db/scheduler/SearchContext.cpp
rename to cpp/src/db/scheduler/context/SearchContext.cpp
index 5bc27f06df3c7dac2879870794594aa496d03f65..493005f05a0351279540b8ba0e11342b8545ab7f 100644
--- a/cpp/src/db/scheduler/SearchContext.cpp
+++ b/cpp/src/db/scheduler/context/SearchContext.cpp
@@ -14,7 +14,8 @@ namespace milvus {
 namespace engine {
 
 SearchContext::SearchContext(uint64_t topk, uint64_t nq, const float* vectors)
-    : topk_(topk),
+    : IScheduleContext(ScheduleContextType::kSearch),
+      topk_(topk),
       nq_(nq),
       vectors_(vectors) {
     //use current time to identify this context
diff --git a/cpp/src/db/scheduler/SearchContext.h b/cpp/src/db/scheduler/context/SearchContext.h
similarity index 95%
rename from cpp/src/db/scheduler/SearchContext.h
rename to cpp/src/db/scheduler/context/SearchContext.h
index 72cbfa4f99d5c71f03a36eb3d17d0d3d19fbca92..1997b807640fa454d2589df8a6cce2eae63509f0 100644
--- a/cpp/src/db/scheduler/SearchContext.h
+++ b/cpp/src/db/scheduler/context/SearchContext.h
@@ -5,6 +5,7 @@
  ******************************************************************************/
 #pragma once
 
+#include "IScheduleContext.h"
 #include "db/MetaTypes.h"
 
 #include <unordered_map>
@@ -18,7 +19,7 @@ namespace engine {
 
 using TableFileSchemaPtr = std::shared_ptr<meta::TableFileSchema>;
 
-class SearchContext {
+class SearchContext : public IScheduleContext {
 public:
     SearchContext(uint64_t topk, uint64_t nq, const float* vectors);
 
diff --git a/cpp/src/db/scheduler/task/DeleteTask.cpp b/cpp/src/db/scheduler/task/DeleteTask.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..a4660fc15756f38ef9f1ac3a158793dac4854d5f
--- /dev/null
+++ b/cpp/src/db/scheduler/task/DeleteTask.cpp
@@ -0,0 +1,30 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+
+#include "DeleteTask.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+DeleteTask::DeleteTask(const DeleteContextPtr& context)
+    : IScheduleTask(ScheduleTaskType::kDelete),
+      context_(context) {
+
+}
+
+std::shared_ptr<IScheduleTask> DeleteTask::Execute() {
+
+    if(context_ != nullptr && context_->meta() != nullptr) {
+        context_->meta()->DeleteTableFiles(context_->table_id());
+    }
+
+    return nullptr;
+}
+
+}
+}
+}
\ No newline at end of file
diff --git a/cpp/src/db/scheduler/IScheduleStrategy.h b/cpp/src/db/scheduler/task/DeleteTask.h
similarity index 57%
rename from cpp/src/db/scheduler/IScheduleStrategy.h
rename to cpp/src/db/scheduler/task/DeleteTask.h
index a619c2a45ea48c8af411af7c8887dd3c4719f129..4617a943bb4545a31a7daadfc46cd20ad89f2519 100644
--- a/cpp/src/db/scheduler/IScheduleStrategy.h
+++ b/cpp/src/db/scheduler/task/DeleteTask.h
@@ -5,22 +5,25 @@
  ******************************************************************************/
 #pragma once
 
-#include "IndexLoaderQueue.h"
-#include "SearchContext.h"
+#include "IScheduleTask.h"
+#include "db/scheduler/context/DeleteContext.h"
 
 namespace zilliz {
 namespace milvus {
 namespace engine {
 
-class IScheduleStrategy {
+class DeleteTask : public IScheduleTask {
 public:
-    virtual ~IScheduleStrategy() {}
+    DeleteTask(const DeleteContextPtr& context);
 
-    virtual bool Schedule(const SearchContextPtr &search_context, IndexLoaderQueue::LoaderQueue& loader_list) = 0;
+    virtual std::shared_ptr<IScheduleTask> Execute() override;
+
+private:
+    DeleteContextPtr context_;
 };
 
-using ScheduleStrategyPtr = std::shared_ptr<IScheduleStrategy>;
+using DeleteTaskPtr = std::shared_ptr<DeleteTask>;
 
 }
 }
-}
\ No newline at end of file
+}
diff --git a/cpp/src/db/scheduler/task/IScheduleTask.h b/cpp/src/db/scheduler/task/IScheduleTask.h
new file mode 100644
index 0000000000000000000000000000000000000000..652a1739fe1294bb8369d898e1ad367cf3385dd3
--- /dev/null
+++ b/cpp/src/db/scheduler/task/IScheduleTask.h
@@ -0,0 +1,41 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+#pragma once
+
+#include <memory>
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+enum class ScheduleTaskType {
+    kUnknown = 0,
+    kIndexLoad,
+    kSearch,
+    kDelete,
+};
+
+class IScheduleTask {
+public:
+    IScheduleTask(ScheduleTaskType type)
+    : type_(type) {
+    }
+
+    virtual ~IScheduleTask() = default;
+
+    ScheduleTaskType type() const { return type_; }
+
+    virtual std::shared_ptr<IScheduleTask> Execute() = 0;
+
+protected:
+    ScheduleTaskType type_;
+};
+
+using ScheduleTaskPtr = std::shared_ptr<IScheduleTask>;
+
+}
+}
+}
diff --git a/cpp/src/db/scheduler/task/IndexLoadTask.cpp b/cpp/src/db/scheduler/task/IndexLoadTask.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..91f0e26577b4f468345c63aca06fc770e8bd4731
--- /dev/null
+++ b/cpp/src/db/scheduler/task/IndexLoadTask.cpp
@@ -0,0 +1,72 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+
+#include "IndexLoadTask.h"
+#include "SearchTask.h"
+#include "db/Log.h"
+#include "db/EngineFactory.h"
+#include "utils/TimeRecorder.h"
+#include "metrics/Metrics.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+namespace {
+void CollectFileMetrics(int file_type, size_t file_size) {
+    switch(file_type) {
+        case meta::TableFileSchema::RAW:
+        case meta::TableFileSchema::TO_INDEX: {
+            server::Metrics::GetInstance().RawFileSizeHistogramObserve(file_size);
+            server::Metrics::GetInstance().RawFileSizeTotalIncrement(file_size);
+            server::Metrics::GetInstance().RawFileSizeGaugeSet(file_size);
+            break;
+        }
+        default: {
+            server::Metrics::GetInstance().IndexFileSizeHistogramObserve(file_size);
+            server::Metrics::GetInstance().IndexFileSizeTotalIncrement(file_size);
+            server::Metrics::GetInstance().IndexFileSizeGaugeSet(file_size);
+            break;
+        }
+    }
+}
+}
+
+IndexLoadTask::IndexLoadTask()
+    : IScheduleTask(ScheduleTaskType::kIndexLoad) {
+
+}
+
+std::shared_ptr<IScheduleTask> IndexLoadTask::Execute() {
+    ENGINE_LOG_INFO << "Loading index(" << file_->id_ << ") from location: " << file_->location_;
+
+    server::TimeRecorder rc("Load index");
+    //step 1: load index
+    ExecutionEnginePtr index_ptr = EngineFactory::Build(file_->dimension_,
+                                                        file_->location_,
+                                                        (EngineType)file_->engine_type_);
+    index_ptr->Load();
+
+    rc.Record("load index file to memory");
+
+    size_t file_size = index_ptr->PhysicalSize();
+    LOG(DEBUG) << "Index file type " << file_->file_type_ << " Of Size: "
+               << file_size/(1024*1024) << " M";
+
+    CollectFileMetrics(file_->file_type_, file_size);
+
+    //step 2: return search task for later execution
+    SearchTaskPtr task_ptr = std::make_shared<SearchTask>();
+    task_ptr->index_id_ = file_->id_;
+    task_ptr->index_type_ = file_->file_type_;
+    task_ptr->index_engine_ = index_ptr;
+    task_ptr->search_contexts_.swap(search_contexts_);
+    return std::static_pointer_cast<IScheduleTask>(task_ptr);
+}
+
+}
+}
+}
\ No newline at end of file
diff --git a/cpp/src/db/scheduler/task/IndexLoadTask.h b/cpp/src/db/scheduler/task/IndexLoadTask.h
new file mode 100644
index 0000000000000000000000000000000000000000..c3548d7311bc8b0ce7b36717c8951c841a1dfa05
--- /dev/null
+++ b/cpp/src/db/scheduler/task/IndexLoadTask.h
@@ -0,0 +1,30 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+#pragma once
+
+#include "IScheduleTask.h"
+#include "db/scheduler/context/SearchContext.h"
+
+namespace zilliz {
+namespace milvus {
+namespace engine {
+
+class IndexLoadTask : public IScheduleTask {
+public:
+    IndexLoadTask();
+
+    virtual std::shared_ptr<IScheduleTask> Execute() override;
+
+public:
+    TableFileSchemaPtr file_;
+    std::vector<SearchContextPtr> search_contexts_;
+};
+
+using IndexLoadTaskPtr = std::shared_ptr<IndexLoadTask>;
+
+}
+}
+}
diff --git a/cpp/src/db/scheduler/SearchTask.cpp b/cpp/src/db/scheduler/task/SearchTask.cpp
similarity index 82%
rename from cpp/src/db/scheduler/SearchTask.cpp
rename to cpp/src/db/scheduler/task/SearchTask.cpp
index 45503490d137ff5367987066c9ad81eb25fbc37b..d8c372699bfe70474005a4c58047d7496ea34490 100644
--- a/cpp/src/db/scheduler/SearchTask.cpp
+++ b/cpp/src/db/scheduler/task/SearchTask.cpp
@@ -4,6 +4,7 @@
  * Proprietary and confidential.
  ******************************************************************************/
 #include "SearchTask.h"
+#include "metrics/Metrics.h"
 #include "utils/Log.h"
 #include "utils/TimeRecorder.h"
 
@@ -110,15 +111,42 @@ void TopkResult(SearchContext::ResultSet &result_src,
     }
 }
 
+void CollectDurationMetrics(int index_type, double total_time) {
+    switch(index_type) {
+        case meta::TableFileSchema::RAW: {
+            server::Metrics::GetInstance().SearchRawDataDurationSecondsHistogramObserve(total_time);
+            break;
+        }
+        case meta::TableFileSchema::TO_INDEX: {
+            server::Metrics::GetInstance().SearchRawDataDurationSecondsHistogramObserve(total_time);
+            break;
+        }
+        default: {
+            server::Metrics::GetInstance().SearchIndexDataDurationSecondsHistogramObserve(total_time);
+            break;
+        }
+    }
 }
 
-bool SearchTask::DoSearch() {
+}
+
+SearchTask::SearchTask()
+: IScheduleTask(ScheduleTaskType::kSearch) {
+
+}
+
+std::shared_ptr<IScheduleTask> SearchTask::Execute() {
     if(index_engine_ == nullptr) {
-        return false;
+        return nullptr;
     }
 
+    SERVER_LOG_INFO << "Searching in index(" << index_id_<< ") with "
+                    << search_contexts_.size() << " tasks";
+
     server::TimeRecorder rc("DoSearch index(" + std::to_string(index_id_) + ")");
 
+    auto start_time = METRICS_NOW_TIME;
+
     std::vector<long> output_ids;
     std::vector<float> output_distence;
     for(auto& context : search_contexts_) {
@@ -153,9 +181,13 @@ bool SearchTask::DoSearch() {
         context->IndexSearchDone(index_id_);
     }
 
+    auto end_time = METRICS_NOW_TIME;
+    auto total_time = METRICS_MICROSECONDS(start_time, end_time);
+    CollectDurationMetrics(index_type_, total_time);
+
     rc.Elapse("totally cost");
 
-    return true;
+    return nullptr;
 }
 
 }
diff --git a/cpp/src/db/scheduler/SearchTask.h b/cpp/src/db/scheduler/task/SearchTask.h
similarity index 77%
rename from cpp/src/db/scheduler/SearchTask.h
rename to cpp/src/db/scheduler/task/SearchTask.h
index 3513c15a3e9a8eebfcc8979302d35ff0fad623e5..0b3a236ce47c1497ab3b10b626987184bfb90ca5 100644
--- a/cpp/src/db/scheduler/SearchTask.h
+++ b/cpp/src/db/scheduler/task/SearchTask.h
@@ -5,19 +5,19 @@
  ******************************************************************************/
 #pragma once
 
-#include "SearchContext.h"
-#include "utils/BlockingQueue.h"
+#include "IScheduleTask.h"
+#include "db/scheduler/context/SearchContext.h"
 #include "db/ExecutionEngine.h"
 
-#include <memory>
-
 namespace zilliz {
 namespace milvus {
 namespace engine {
 
-class SearchTask {
+class SearchTask : public IScheduleTask {
 public:
-    bool DoSearch();
+    SearchTask();
+
+    virtual std::shared_ptr<IScheduleTask> Execute() override;
 
 public:
     size_t index_id_ = 0;
diff --git a/cpp/src/sdk/examples/simple/src/ClientTest.cpp b/cpp/src/sdk/examples/simple/src/ClientTest.cpp
index b2ed9f3b25ff05a7fac33c5227ea044c9fa1ede5..3aad4e0789105eaba3c2e40b55c110008ddb06f6 100644
--- a/cpp/src/sdk/examples/simple/src/ClientTest.cpp
+++ b/cpp/src/sdk/examples/simple/src/ClientTest.cpp
@@ -20,7 +20,7 @@ namespace {
     static constexpr int64_t TOTAL_ROW_COUNT = 100000;
     static constexpr int64_t TOP_K = 10;
     static constexpr int64_t SEARCH_TARGET = 5000; //change this value, result is different
-    static constexpr int64_t ADD_VECTOR_LOOP = 2;
+    static constexpr int64_t ADD_VECTOR_LOOP = 10;
 
 #define BLOCK_SPLITER std::cout << "===========================================" << std::endl;
 
@@ -195,10 +195,10 @@ ClientTest::Test(const std::string& address, const std::string& port) {
         PrintSearchResult(topk_query_result_array);
     }
 
-//    {//delete table
-//        Status stat = conn->DeleteTable(TABLE_NAME);
-//        std::cout << "DeleteTable function call status: " << stat.ToString() << std::endl;
-//    }
+    {//delete table
+        Status stat = conn->DeleteTable(TABLE_NAME);
+        std::cout << "DeleteTable function call status: " << stat.ToString() << std::endl;
+    }
 
     {//server status
         std::string status = conn->ServerStatus();
diff --git a/cpp/src/server/DBWrapper.cpp b/cpp/src/server/DBWrapper.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..4cae31ea6b51b26066498b149b65a81ff18f3505
--- /dev/null
+++ b/cpp/src/server/DBWrapper.cpp
@@ -0,0 +1,42 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+
+#include "DBWrapper.h"
+#include "ServerConfig.h"
+#include "utils/CommonUtil.h"
+#include "utils/Log.h"
+
+namespace zilliz {
+namespace milvus {
+namespace server {
+
+DBWrapper::DBWrapper() {
+    zilliz::milvus::engine::Options opt;
+    ConfigNode& config = ServerConfig::GetInstance().GetConfig(CONFIG_DB);
+    opt.meta.backend_uri = config.GetValue(CONFIG_DB_URL);
+    std::string db_path = config.GetValue(CONFIG_DB_PATH);
+    opt.meta.path = db_path + "/db";
+    int64_t index_size = config.GetInt64Value(CONFIG_DB_INDEX_TRIGGER_SIZE);
+    if(index_size > 0) {//ensure larger than zero, unit is MB
+        opt.index_trigger_size = (size_t)index_size * engine::ONE_MB;
+    }
+
+    CommonUtil::CreateDirectory(opt.meta.path);
+
+    zilliz::milvus::engine::DB::Open(opt, &db_);
+    if(db_ == nullptr) {
+        SERVER_LOG_ERROR << "Failed to open db";
+        throw ServerException(SERVER_NULL_POINTER, "Failed to open db");
+    }
+}
+
+DBWrapper::~DBWrapper() {
+    delete db_;
+}
+
+}
+}
+}
\ No newline at end of file
diff --git a/cpp/src/server/DBWrapper.h b/cpp/src/server/DBWrapper.h
new file mode 100644
index 0000000000000000000000000000000000000000..5bd09bd0f4e32b5dcdb4798fc63c46948db7e11a
--- /dev/null
+++ b/cpp/src/server/DBWrapper.h
@@ -0,0 +1,34 @@
+/*******************************************************************************
+ * Copyright 上海赜睿信息科技有限公司(Zilliz) - All Rights Reserved
+ * Unauthorized copying of this file, via any medium is strictly prohibited.
+ * Proprietary and confidential.
+ ******************************************************************************/
+#pragma once
+
+#include "db/DB.h"
+#include "db/Meta.h"
+
+namespace zilliz {
+namespace milvus {
+namespace server {
+
+class DBWrapper {
+private:
+    DBWrapper();
+    ~DBWrapper();
+
+public:
+    static zilliz::milvus::engine::DB* DB() {
+        static DBWrapper db_wrapper;
+        return db_wrapper.db();
+    }
+
+    zilliz::milvus::engine::DB* db() { return db_; }
+
+private:
+    zilliz::milvus::engine::DB* db_ = nullptr;
+};
+
+}
+}
+}
diff --git a/cpp/src/server/MilvusServer.cpp b/cpp/src/server/MilvusServer.cpp
index 2b46627ad0092e5770a289dd8e770a9a961e71a6..f738c46711e010e9b2c389354747b97c29ec00b8 100644
--- a/cpp/src/server/MilvusServer.cpp
+++ b/cpp/src/server/MilvusServer.cpp
@@ -7,6 +7,7 @@
 #include "RequestHandler.h"
 #include "ServerConfig.h"
 #include "ThreadPoolServer.h"
+#include "DBWrapper.h"
 
 #include "milvus_types.h"
 #include "milvus_constants.h"
@@ -51,6 +52,8 @@ MilvusServer::StartService() {
     std::string mode = server_config.GetValue(CONFIG_SERVER_MODE, "thread_pool");
 
     try {
+        DBWrapper::DB();//initialize db
+
         stdcxx::shared_ptr<RequestHandler> handler(new RequestHandler());
         stdcxx::shared_ptr<TProcessor> processor(new MilvusServiceProcessor(handler));
         stdcxx::shared_ptr<TServerTransport> server_transport(new TServerSocket(address, port));
diff --git a/cpp/src/server/RequestTask.cpp b/cpp/src/server/RequestTask.cpp
index 3133e1cd80c4157a32a822a2ff1219243dfeee67..dbe4e6a7406ebd0b512608fe3b2b6123344fd442 100644
--- a/cpp/src/server/RequestTask.cpp
+++ b/cpp/src/server/RequestTask.cpp
@@ -8,8 +8,7 @@
 #include "utils/CommonUtil.h"
 #include "utils/Log.h"
 #include "utils/TimeRecorder.h"
-#include "db/DB.h"
-#include "db/Meta.h"
+#include "DBWrapper.h"
 #include "version.h"
 
 namespace zilliz {
@@ -26,43 +25,6 @@ using DB_META = zilliz::milvus::engine::meta::Meta;
 using DB_DATE = zilliz::milvus::engine::meta::DateT;
 
 namespace {
-    class DBWrapper {
-    public:
-        DBWrapper() {
-            zilliz::milvus::engine::Options opt;
-            ConfigNode& config = ServerConfig::GetInstance().GetConfig(CONFIG_DB);
-            opt.meta.backend_uri = config.GetValue(CONFIG_DB_URL);
-            std::string db_path = config.GetValue(CONFIG_DB_PATH);
-            opt.meta.path = db_path + "/db";
-            int64_t index_size = config.GetInt64Value(CONFIG_DB_INDEX_TRIGGER_SIZE);
-            if(index_size > 0) {//ensure larger than zero, unit is MB
-                opt.index_trigger_size = (size_t)index_size * engine::ONE_MB;
-            }
-
-            CommonUtil::CreateDirectory(opt.meta.path);
-
-            zilliz::milvus::engine::DB::Open(opt, &db_);
-            if(db_ == nullptr) {
-                SERVER_LOG_ERROR << "Failed to open db";
-                throw ServerException(SERVER_NULL_POINTER, "Failed to open db");
-            }
-        }
-
-        ~DBWrapper() {
-            delete db_;
-        }
-
-        zilliz::milvus::engine::DB* DB() { return db_; }
-
-    private:
-        zilliz::milvus::engine::DB* db_ = nullptr;
-    };
-
-    zilliz::milvus::engine::DB* DB() {
-        static DBWrapper db_wrapper;
-        return db_wrapper.DB();
-    }
-
     engine::EngineType EngineType(int type) {
         static std::map<int, engine::EngineType> map_type = {
                 {0, engine::EngineType::INVALID},
@@ -199,7 +161,7 @@ ServerError CreateTableTask::OnExecute() {
         table_info.store_raw_data_ = schema_.store_raw_vector;
 
         //step 3: create table
-        engine::Status stat = DB()->CreateTable(table_info);
+        engine::Status stat = DBWrapper::DB()->CreateTable(table_info);
         if(!stat.ok()) {//table could exist
             error_code_ = SERVER_UNEXPECTED_ERROR;
             error_msg_ = "Engine failed: " + stat.ToString();
@@ -246,7 +208,7 @@ ServerError DescribeTableTask::OnExecute() {
         //step 2: get table info
         engine::meta::TableSchema table_info;
         table_info.table_id_ = table_name_;
-        engine::Status stat = DB()->DescribeTable(table_info);
+        engine::Status stat = DBWrapper::DB()->DescribeTable(table_info);
         if(!stat.ok()) {
             error_code_ = SERVER_TABLE_NOT_EXIST;
             error_msg_ = "Engine failed: " + stat.ToString();
@@ -297,7 +259,7 @@ ServerError DeleteTableTask::OnExecute() {
         //step 2: check table existence
         engine::meta::TableSchema table_info;
         table_info.table_id_ = table_name_;
-        engine::Status stat = DB()->DescribeTable(table_info);
+        engine::Status stat = DBWrapper::DB()->DescribeTable(table_info);
         if(!stat.ok()) {
             error_code_ = SERVER_TABLE_NOT_EXIST;
             error_msg_ = "Engine failed: " + stat.ToString();
@@ -309,7 +271,7 @@ ServerError DeleteTableTask::OnExecute() {
 
         //step 3: delete table
         std::vector<DB_DATE> dates;
-        stat = DB()->DeleteTable(table_name_, dates);
+        stat = DBWrapper::DB()->DeleteTable(table_name_, dates);
         if(!stat.ok()) {
             SERVER_LOG_ERROR << "Engine failed: " << stat.ToString();
             return SERVER_UNEXPECTED_ERROR;
@@ -340,7 +302,7 @@ BaseTaskPtr ShowTablesTask::Create(std::vector<std::string>& tables) {
 
 ServerError ShowTablesTask::OnExecute() {
     std::vector<engine::meta::TableSchema> schema_array;
-    engine::Status stat = DB()->AllTables(schema_array);
+    engine::Status stat = DBWrapper::DB()->AllTables(schema_array);
     if(!stat.ok()) {
         error_code_ = SERVER_UNEXPECTED_ERROR;
         error_msg_ = "Engine failed: " + stat.ToString();
@@ -395,7 +357,7 @@ ServerError AddVectorTask::OnExecute() {
         //step 2: check table existence
         engine::meta::TableSchema table_info;
         table_info.table_id_ = table_name_;
-        engine::Status stat = DB()->DescribeTable(table_info);
+        engine::Status stat = DBWrapper::DB()->DescribeTable(table_info);
         if(!stat.ok()) {
             error_code_ = SERVER_TABLE_NOT_EXIST;
             error_msg_ = "Engine failed: " + stat.ToString();
@@ -417,7 +379,7 @@ ServerError AddVectorTask::OnExecute() {
 
         //step 4: insert vectors
         uint64_t vec_count = (uint64_t)record_array_.size();
-        stat = DB()->InsertVectors(table_name_, vec_count, vec_f.data(), record_ids_);
+        stat = DBWrapper::DB()->InsertVectors(table_name_, vec_count, vec_f.data(), record_ids_);
         rc.Record("add vectors to engine");
         if(!stat.ok()) {
             error_code_ = SERVER_UNEXPECTED_ERROR;
@@ -493,7 +455,7 @@ ServerError SearchVectorTask::OnExecute() {
         //step 2: check table existence
         engine::meta::TableSchema table_info;
         table_info.table_id_ = table_name_;
-        engine::Status stat = DB()->DescribeTable(table_info);
+        engine::Status stat = DBWrapper::DB()->DescribeTable(table_info);
         if(!stat.ok()) {
             error_code_ = SERVER_TABLE_NOT_EXIST;
             error_msg_ = "Engine failed: " + stat.ToString();
@@ -526,9 +488,9 @@ ServerError SearchVectorTask::OnExecute() {
         uint64_t record_count = (uint64_t)record_array_.size();
 
         if(file_id_array_.empty()) {
-            stat = DB()->Query(table_name_, (size_t) top_k_, record_count, vec_f.data(), dates, results);
+            stat = DBWrapper::DB()->Query(table_name_, (size_t) top_k_, record_count, vec_f.data(), dates, results);
         } else {
-            stat = DB()->Query(table_name_, file_id_array_, (size_t) top_k_, record_count, vec_f.data(), dates, results);
+            stat = DBWrapper::DB()->Query(table_name_, file_id_array_, (size_t) top_k_, record_count, vec_f.data(), dates, results);
         }
 
         rc.Record("search vectors from engine");
@@ -599,7 +561,7 @@ ServerError GetTableRowCountTask::OnExecute() {
 
         //step 2: get row count
         uint64_t row_count = 0;
-        engine::Status stat = DB()->GetTableRowCount(table_name_, row_count);
+        engine::Status stat = DBWrapper::DB()->GetTableRowCount(table_name_, row_count);
         if (!stat.ok()) {
             error_code_ = SERVER_UNEXPECTED_ERROR;
             error_msg_ = "Engine failed: " + stat.ToString();
diff --git a/cpp/unittest/db/CMakeLists.txt b/cpp/unittest/db/CMakeLists.txt
index 67ef5fccec0bc1cf6739d98a23db22e286e21c36..df47f14c659426d003c13588a3549acd67757eb9 100644
--- a/cpp/unittest/db/CMakeLists.txt
+++ b/cpp/unittest/db/CMakeLists.txt
@@ -4,11 +4,19 @@
 # Proprietary and confidential.
 #-------------------------------------------------------------------------------
 aux_source_directory(${MILVUS_ENGINE_SRC}/db db_srcs)
-aux_source_directory(${MILVUS_ENGINE_SRC}/db/scheduler db_scheduler_srcs)
 aux_source_directory(${MILVUS_ENGINE_SRC}/config config_files)
 aux_source_directory(${MILVUS_ENGINE_SRC}/cache cache_srcs)
 aux_source_directory(${MILVUS_ENGINE_SRC}/wrapper wrapper_src)
 
+aux_source_directory(${MILVUS_ENGINE_SRC}/db/scheduler scheduler_files)
+aux_source_directory(${MILVUS_ENGINE_SRC}/db/scheduler/context scheduler_context_files)
+aux_source_directory(${MILVUS_ENGINE_SRC}/db/scheduler/task scheduler_task_files)
+set(db_scheduler_srcs
+        ${scheduler_files}
+        ${scheduler_context_files}
+        ${scheduler_task_files}
+        )
+
 include_directories(/usr/local/cuda/include)
 link_directories("/usr/local/cuda/lib64")
 
diff --git a/cpp/unittest/metrics/CMakeLists.txt b/cpp/unittest/metrics/CMakeLists.txt
index 2f07cbed242a90e26c5f8e114c31d82f36de9cfb..9ae711ce252f424d12b47c66123f7071b58ea38a 100644
--- a/cpp/unittest/metrics/CMakeLists.txt
+++ b/cpp/unittest/metrics/CMakeLists.txt
@@ -13,12 +13,19 @@ include_directories(../../src)
 
 
 aux_source_directory(../../src/db db_srcs)
-aux_source_directory(../../src/db/scheduler db_scheduler_srcs)
 aux_source_directory(../../src/config config_files)
 aux_source_directory(../../src/cache cache_srcs)
 aux_source_directory(../../src/wrapper wrapper_src)
 aux_source_directory(../../src/metrics metrics_src)
 
+aux_source_directory(${MILVUS_ENGINE_SRC}/db/scheduler scheduler_files)
+aux_source_directory(${MILVUS_ENGINE_SRC}/db/scheduler/context scheduler_context_files)
+aux_source_directory(${MILVUS_ENGINE_SRC}/db/scheduler/task scheduler_task_files)
+set(db_scheduler_srcs
+        ${scheduler_files}
+        ${scheduler_context_files}
+        ${scheduler_task_files}
+        )
 
 include_directories(/usr/include)
 include_directories(../../third_party/build/include)