diff --git a/cpp/CHANGELOG.md b/cpp/CHANGELOG.md
index 99d55ea524f4a29e1df9702a22c805c254cd579f..879094b8d1bdffef30b8b9a1f7fb33096e9e5269 100644
--- a/cpp/CHANGELOG.md
+++ b/cpp/CHANGELOG.md
@@ -10,6 +10,10 @@ Please mark all change in change log and use the ticket from JIRA.
 - MS-416 - ExecutionEngineImpl::GpuCache has not return value cause crash
 - MS-417 - YAML sequence load disable cause scheduler startup failed
 - MS-413 - Create index failed and server exited
+- MS-427 - Describe index error after drop index
+- MS-432 - Search vectors params nprobe need to check max number
+- MS-431 - Search vectors params nprobe: 0/-1, expected result: raise exception
+- MS-331 - Crate Table : when table exists, error code is META_FAILED(code=15) rather than ILLEGAL TABLE NAME(code=9))
 
 ## Improvement
 - MS-327 - Clean code for milvus
diff --git a/cpp/src/db/DB.h b/cpp/src/db/DB.h
index f42154174166e4741c32bc2c0e57bf20e23a3f5c..908714a08a61a8a7e50a379b49bbf8f413f09b12 100644
--- a/cpp/src/db/DB.h
+++ b/cpp/src/db/DB.h
@@ -46,7 +46,6 @@ public:
 
     virtual Status Size(uint64_t& result) = 0;
 
-    virtual Status BuildIndex(const std::string& table_id) = 0;
     virtual Status CreateIndex(const std::string& table_id, const TableIndex& index) = 0;
     virtual Status DescribeIndex(const std::string& table_id, TableIndex& index) = 0;
     virtual Status DropIndex(const std::string& table_id) = 0;
diff --git a/cpp/src/db/DBImpl.cpp b/cpp/src/db/DBImpl.cpp
index a9386ff1eb8e865ccfd3579be2c6e930621c3fb7..168522e21d0287a35d636af06f197881d2c5fd31 100644
--- a/cpp/src/db/DBImpl.cpp
+++ b/cpp/src/db/DBImpl.cpp
@@ -424,7 +424,14 @@ Status DBImpl::MergeFiles(const std::string& table_id, const meta::DateT& date,
     }
 
     //step 4: update table files state
-    table_file.file_type_ = meta::TableFileSchema::RAW;
+    //if index type isn't IDMAP, set file type to TO_INDEX if file size execeed index_file_size
+    //else set file type to RAW, no need to build index
+    if (table_file.engine_type_ != (int)EngineType::FAISS_IDMAP) {
+        table_file.file_type_ = (index->PhysicalSize() >= table_file.index_file_size_) ?
+                                meta::TableFileSchema::TO_INDEX : meta::TableFileSchema::RAW;
+    } else {
+        table_file.file_type_ = meta::TableFileSchema::RAW;
+    }
     table_file.file_size_ = index->PhysicalSize();
     table_file.row_count_ = index->Count();
     updated.push_back(table_file);
@@ -516,22 +523,6 @@ void DBImpl::StartBuildIndexTask(bool force) {
     }
 }
 
-Status DBImpl::BuildIndex(const std::string& table_id) {
-    bool has = false;
-    meta_ptr_->HasNonIndexFiles(table_id, has);
-    int times = 1;
-
-    while (has) {
-        ENGINE_LOG_DEBUG << "Non index files detected in " << table_id << "! Will build index " << times;
-        meta_ptr_->UpdateTableFilesToIndex(table_id);
-        /* StartBuildIndexTask(true); */
-        std::this_thread::sleep_for(std::chrono::milliseconds(std::min(10*1000, times*100)));
-        meta_ptr_->HasNonIndexFiles(table_id, has);
-        times++;
-    }
-    return Status::OK();
-}
-
 Status DBImpl::CreateIndex(const std::string& table_id, const TableIndex& index) {
     {
         std::unique_lock<std::mutex> lock(build_index_mutex_);
@@ -552,18 +543,17 @@ Status DBImpl::CreateIndex(const std::string& table_id, const TableIndex& index)
         //step 2: drop old index files
         DropIndex(table_id);
 
-        if(index.engine_type_ == (int)EngineType::FAISS_IDMAP) {
-            ENGINE_LOG_DEBUG << "index type = IDMAP, no need to build index";
-            return Status::OK();
-        }
-
         //step 3: update index info
-
         status = meta_ptr_->UpdateTableIndexParam(table_id, index);
         if (!status.ok()) {
             ENGINE_LOG_ERROR << "Failed to update table index info";
             return status;
         }
+
+        if(index.engine_type_ == (int)EngineType::FAISS_IDMAP) {
+            ENGINE_LOG_DEBUG << "index type = IDMAP, no need to build index";
+            return Status::OK();
+        }
     }
 
     bool has = false;
diff --git a/cpp/src/db/DBImpl.h b/cpp/src/db/DBImpl.h
index 65ac489c49ac3e6f9e9e658575b2e8692f04e16d..a6e52bd3c3bce3aa0cb8398662f0ac65e78e2830 100644
--- a/cpp/src/db/DBImpl.h
+++ b/cpp/src/db/DBImpl.h
@@ -82,8 +82,6 @@ class DBImpl : public DB {
 
     Status Size(uint64_t &result) override;
 
-    Status BuildIndex(const std::string& table_id) override;
-
     Status CreateIndex(const std::string& table_id, const TableIndex& index) override;
 
     Status DescribeIndex(const std::string& table_id, TableIndex& index) override;
diff --git a/cpp/src/db/Status.cpp b/cpp/src/db/Status.cpp
index 76c72fac62e9326fe05f7e68e9b456ee5a01ab76..65524c62a96878fd6837a2473768274acf42795c 100644
--- a/cpp/src/db/Status.cpp
+++ b/cpp/src/db/Status.cpp
@@ -48,6 +48,21 @@ std::string Status::ToString() const {
         case kNotFound:
             type = "NotFound: ";
             break;
+        case kError:
+            type = "Error: ";
+            break;
+        case kInvalidDBPath:
+            type = "InvalidDBPath: ";
+            break;
+        case kGroupError:
+            type = "GroupError: ";
+            break;
+        case kDBTransactionError:
+            type = "DBTransactionError: ";
+            break;
+        case kAlreadyExist:
+            type = "AlreadyExist: ";
+            break;
         default:
             snprintf(tmp, sizeof(tmp), "Unkown code(%d): ",
                     static_cast<int>(code()));
diff --git a/cpp/src/db/insert/MemTableFile.cpp b/cpp/src/db/insert/MemTableFile.cpp
index 48e52d0d9b333639bff0e61d2109849cf174e77d..2054a5047e30cba72166583f860b0d1430736d5e 100644
--- a/cpp/src/db/insert/MemTableFile.cpp
+++ b/cpp/src/db/insert/MemTableFile.cpp
@@ -87,8 +87,14 @@ Status MemTableFile::Serialize() {
     table_file_schema_.file_size_ = execution_engine_->PhysicalSize();
     table_file_schema_.row_count_ = execution_engine_->Count();
 
-    table_file_schema_.file_type_ = (size >= table_file_schema_.index_file_size_) ?
-                                    meta::TableFileSchema::TO_INDEX : meta::TableFileSchema::RAW;
+    //if index type isn't IDMAP, set file type to TO_INDEX if file size execeed index_file_size
+    //else set file type to RAW, no need to build index
+    if (table_file_schema_.engine_type_ != (int)EngineType::FAISS_IDMAP) {
+        table_file_schema_.file_type_ = (size >= table_file_schema_.index_file_size_) ?
+                                        meta::TableFileSchema::TO_INDEX : meta::TableFileSchema::RAW;
+    } else {
+        table_file_schema_.file_type_ = meta::TableFileSchema::RAW;
+    }
 
     auto status = meta_->UpdateTableFile(table_file_schema_);
 
diff --git a/cpp/src/db/meta/MetaTypes.h b/cpp/src/db/meta/MetaTypes.h
index 0727528fe935f5401c2acce79a71ad9736869e8a..a75bcc07dc7652ce244e55e0e4c99dbebb9e0981 100644
--- a/cpp/src/db/meta/MetaTypes.h
+++ b/cpp/src/db/meta/MetaTypes.h
@@ -19,8 +19,8 @@ namespace meta {
 
 constexpr int32_t DEFAULT_ENGINE_TYPE = (int)EngineType::FAISS_IDMAP;
 constexpr int32_t DEFAULT_NLIST = 16384;
-constexpr int32_t DEFAULT_INDEX_FILE_SIZE = ONE_GB;
 constexpr int32_t DEFAULT_METRIC_TYPE = (int)MetricType::L2;
+constexpr int32_t DEFAULT_INDEX_FILE_SIZE = ONE_GB;
 
 constexpr int64_t FLAG_MASK_USERID = 1;
 
diff --git a/cpp/src/db/meta/MySQLMetaImpl.cpp b/cpp/src/db/meta/MySQLMetaImpl.cpp
index 92af8e2a677d9697c7dd9a03302e0908c25d17e4..cb1ec199cf08a8914bce88f46279179d5f2c75f7 100644
--- a/cpp/src/db/meta/MySQLMetaImpl.cpp
+++ b/cpp/src/db/meta/MySQLMetaImpl.cpp
@@ -536,6 +536,7 @@ Status MySQLMetaImpl::DropTableIndex(const std::string &table_id) {
 
             Query dropTableIndexQuery = connectionPtr->query();
 
+            //soft delete index files
             dropTableIndexQuery << "UPDATE TableFiles " <<
                                 "SET file_type = " << std::to_string(TableFileSchema::TO_DELETE) << "," <<
                                 "updated_time = " << utils::GetMicroSecTimeStamp() << " " <<
@@ -550,6 +551,7 @@ Status MySQLMetaImpl::DropTableIndex(const std::string &table_id) {
                                                   dropTableIndexQuery.error());
             }
 
+            //set all backup file to raw
             dropTableIndexQuery << "UPDATE TableFiles " <<
                                 "SET file_type = " << std::to_string(TableFileSchema::RAW) << "," <<
                                 "updated_time = " << utils::GetMicroSecTimeStamp() << " " <<
@@ -564,6 +566,21 @@ Status MySQLMetaImpl::DropTableIndex(const std::string &table_id) {
                                                   dropTableIndexQuery.error());
             }
 
+            //set table index type to raw
+            dropTableIndexQuery << "UPDATE Tables " <<
+                                "SET engine_type = " << std::to_string(DEFAULT_ENGINE_TYPE) << "," <<
+                                "nlist = " << std::to_string(DEFAULT_NLIST) << " " <<
+                                "metric_type = " << std::to_string(DEFAULT_METRIC_TYPE) << " " <<
+                                "WHERE table_id = " << quote << table_id << ";";
+
+            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DropTableIndex: " << dropTableIndexQuery.str();
+
+            if (!dropTableIndexQuery.exec()) {
+                ENGINE_LOG_ERROR << "QUERY ERROR WHEN DROP TABLE INDEX";
+                return Status::DBTransactionError("QUERY ERROR WHEN DROP TABLE INDEX",
+                                                  dropTableIndexQuery.error());
+            }
+
         } //Scoped Connection
 
     } catch (const BadQuery &er) {
diff --git a/cpp/src/db/meta/SqliteMetaImpl.cpp b/cpp/src/db/meta/SqliteMetaImpl.cpp
index a06c391ca5f2c68003313d7fb63413a540e8553c..3f427130ae80e4c0c0140c4833597581d7668a5a 100644
--- a/cpp/src/db/meta/SqliteMetaImpl.cpp
+++ b/cpp/src/db/meta/SqliteMetaImpl.cpp
@@ -461,6 +461,17 @@ Status SqliteMetaImpl::DropTableIndex(const std::string &table_id) {
                         c(&TableFileSchema::file_type_) == (int) TableFileSchema::BACKUP
                 ));
 
+        //set table index type to raw
+        ConnectorPtr->update_all(
+                set(
+                        c(&TableSchema::engine_type_) = DEFAULT_ENGINE_TYPE,
+                        c(&TableSchema::nlist_) = DEFAULT_NLIST,
+                        c(&TableSchema::metric_type_) = DEFAULT_METRIC_TYPE
+                ),
+                where(
+                        c(&TableSchema::table_id_) == table_id
+                ));
+
     } catch (std::exception &e) {
         return HandleException("Encounter exception when delete table index files", e);
     }
@@ -798,11 +809,15 @@ Status SqliteMetaImpl::FilesToSearch(const std::string &table_id,
             }
             files[table_file.date_].push_back(table_file);
         }
-
+        if(files.empty()) {
+            std::cout << "ERROR" << std::endl;
+        }
     } catch (std::exception &e) {
         return HandleException("Encounter exception when iterate index files", e);
     }
 
+
+
     return Status::OK();
 }
 
diff --git a/cpp/src/server/grpc_impl/GrpcRequestScheduler.cpp b/cpp/src/server/grpc_impl/GrpcRequestScheduler.cpp
index ef60aba8a3b16e8c0672a56a689aa5ce228e3bbd..637b4c3b34154fd9c7307c2cf5653ad188f97be2 100644
--- a/cpp/src/server/grpc_impl/GrpcRequestScheduler.cpp
+++ b/cpp/src/server/grpc_impl/GrpcRequestScheduler.cpp
@@ -39,6 +39,9 @@ namespace {
                 {SERVER_INVALID_ROWRECORD,        ::milvus::grpc::ErrorCode::ILLEGAL_ROWRECORD},
                 {SERVER_INVALID_ROWRECORD_ARRAY,  ::milvus::grpc::ErrorCode::ILLEGAL_ROWRECORD},
                 {SERVER_INVALID_TOPK,             ::milvus::grpc::ErrorCode::ILLEGAL_TOPK},
+                {SERVER_INVALID_NPROBE,           ::milvus::grpc::ErrorCode::ILLEGAL_ARGUMENT},
+                {SERVER_INVALID_INDEX_NLIST,      ::milvus::grpc::ErrorCode::ILLEGAL_ARGUMENT},
+                {SERVER_INVALID_INDEX_METRIC_TYPE,::milvus::grpc::ErrorCode::ILLEGAL_ARGUMENT},
                 {SERVER_ILLEGAL_VECTOR_ID,        ::milvus::grpc::ErrorCode::ILLEGAL_VECTOR_ID},
                 {SERVER_ILLEGAL_SEARCH_RESULT,    ::milvus::grpc::ErrorCode::ILLEGAL_SEARCH_RESULT},
                 {SERVER_CACHE_ERROR,              ::milvus::grpc::ErrorCode::CACHE_FAILED},
diff --git a/cpp/src/server/grpc_impl/GrpcRequestTask.cpp b/cpp/src/server/grpc_impl/GrpcRequestTask.cpp
index a4b8d68c296e4066f263ecf41f148e18845e67bc..5489089033e789f05282ebf01e82f7f7d9221a80 100644
--- a/cpp/src/server/grpc_impl/GrpcRequestTask.cpp
+++ b/cpp/src/server/grpc_impl/GrpcRequestTask.cpp
@@ -153,7 +153,10 @@ CreateTableTask::OnExecute() {
         engine::Status stat = DBWrapper::DB()->CreateTable(table_info);
         if (!stat.ok()) {
             //table could exist
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            if(stat.IsAlreadyExist()) {
+                return SetError(SERVER_INVALID_TABLE_NAME, stat.ToString());
+            }
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
     } catch (std::exception &ex) {
@@ -193,7 +196,7 @@ DescribeTableTask::OnExecute() {
         table_info.table_id_ = table_name_;
         engine::Status stat = DBWrapper::DB()->DescribeTable(table_info);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         schema_->mutable_table_name()->set_table_name(table_info.table_id_);
@@ -238,7 +241,7 @@ CreateIndexTask::OnExecute() {
         bool has_table = false;
         engine::Status stat = DBWrapper::DB()->HasTable(table_name_, has_table);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         if (!has_table) {
@@ -268,7 +271,7 @@ CreateIndexTask::OnExecute() {
         index.metric_type_ = grpc_index.metric_type();
         stat = DBWrapper::DB()->CreateIndex(table_name_, index);
         if (!stat.ok()) {
-            return SetError(SERVER_BUILD_INDEX_ERROR, "Engine failed: " + stat.ToString());
+            return SetError(SERVER_BUILD_INDEX_ERROR, stat.ToString());
         }
 
         rc.ElapseFromBegin("totally cost");
@@ -306,7 +309,7 @@ HasTableTask::OnExecute() {
         //step 2: check table existence
         engine::Status stat = DBWrapper::DB()->HasTable(table_name_, has_table_);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         rc.ElapseFromBegin("totally cost");
@@ -348,7 +351,7 @@ DropTableTask::OnExecute() {
             if (stat.IsNotFound()) {
                 return SetError(SERVER_TABLE_NOT_EXIST, "Table " + table_name_ + " not exists");
             } else {
-                return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+                return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
             }
         }
 
@@ -358,7 +361,7 @@ DropTableTask::OnExecute() {
         std::vector<DB_DATE> dates;
         stat = DBWrapper::DB()->DeleteTable(table_name_, dates);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         rc.ElapseFromBegin("total cost");
@@ -386,7 +389,7 @@ ShowTablesTask::OnExecute() {
     std::vector<engine::meta::TableSchema> schema_array;
     engine::Status stat = DBWrapper::DB()->AllTables(schema_array);
     if (!stat.ok()) {
-        return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+        return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
     }
 
     for (auto &schema : schema_array) {
@@ -448,7 +451,7 @@ InsertTask::OnExecute() {
                 return SetError(SERVER_TABLE_NOT_EXIST,
                                 "Table " + insert_param_->table_name() + " not exists");
             } else {
-                return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+                return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
             }
         }
 
@@ -573,28 +576,13 @@ SearchTask::OnExecute() {
     try {
         TimeRecorder rc("SearchTask");
 
-        //step 1: check arguments
+        //step 1: check table name
         std::string table_name_ = search_param_->table_name();
         ServerError res = ValidationUtil::ValidateTableName(table_name_);
         if (res != SERVER_SUCCESS) {
             return SetError(res, "Invalid table name: " + table_name_);
         }
 
-        int64_t top_k_ = search_param_->topk();
-
-        if (top_k_ <= 0 || top_k_ > 1024) {
-            return SetError(SERVER_INVALID_TOPK, "Invalid topk: " + std::to_string(top_k_));
-        }
-
-        int64_t nprobe = search_param_->nprobe();
-        if (nprobe <= 0) {
-            return SetError(SERVER_INVALID_NPROBE, "Invalid nprobe: " + std::to_string(nprobe));
-        }
-
-        if (search_param_->query_record_array().empty()) {
-            return SetError(SERVER_INVALID_ROWRECORD_ARRAY, "Row record array is empty");
-        }
-
         //step 2: check table existence
         engine::meta::TableSchema table_info;
         table_info.table_id_ = table_name_;
@@ -603,11 +591,28 @@ SearchTask::OnExecute() {
             if (stat.IsNotFound()) {
                 return SetError(SERVER_TABLE_NOT_EXIST, "Table " + table_name_ + " not exists");
             } else {
-                return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+                return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
             }
         }
 
-        //step 3: check date range, and convert to db dates
+        //step 3: check search parameter
+        int64_t top_k = search_param_->topk();
+        res = ValidationUtil::ValidateSearchTopk(top_k, table_info);
+        if (res != SERVER_SUCCESS) {
+            return SetError(res, "Invalid topk: " + std::to_string(top_k));
+        }
+
+        int64_t nprobe = search_param_->nprobe();
+        res = ValidationUtil::ValidateSearchNprobe(nprobe, table_info);
+        if (res != SERVER_SUCCESS) {
+            return SetError(res, "Invalid nprobe: " + std::to_string(nprobe));
+        }
+
+        if (search_param_->query_record_array().empty()) {
+            return SetError(SERVER_INVALID_ROWRECORD_ARRAY, "Row record array is empty");
+        }
+
+        //step 4: check date range, and convert to db dates
         std::vector<DB_DATE> dates;
         ServerError error_code = SERVER_SUCCESS;
         std::string error_msg;
@@ -630,7 +635,7 @@ SearchTask::OnExecute() {
         ProfilerStart(fname.c_str());
 #endif
 
-        //step 3: prepare float data
+        //step 5: prepare float data
         auto record_array_size = search_param_->query_record_array_size();
         std::vector<float> vec_f(record_array_size * table_info.dimension_, 0);
         for (size_t i = 0; i < record_array_size; i++) {
@@ -651,21 +656,21 @@ SearchTask::OnExecute() {
         }
         rc.ElapseFromBegin("prepare vector data");
 
-        //step 4: search vectors
+        //step 6: search vectors
         engine::QueryResults results;
         auto record_count = (uint64_t) search_param_->query_record_array().size();
 
         if (file_id_array_.empty()) {
-            stat = DBWrapper::DB()->Query(table_name_, (size_t) top_k_, record_count, nprobe, vec_f.data(),
+            stat = DBWrapper::DB()->Query(table_name_, (size_t) top_k, record_count, nprobe, vec_f.data(),
                                           dates, results);
         } else {
-            stat = DBWrapper::DB()->Query(table_name_, file_id_array_, (size_t) top_k_,
+            stat = DBWrapper::DB()->Query(table_name_, file_id_array_, (size_t) top_k,
                                           record_count, nprobe, vec_f.data(), dates, results);
         }
 
         rc.ElapseFromBegin("search vectors from engine");
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         if (results.empty()) {
@@ -680,7 +685,7 @@ SearchTask::OnExecute() {
 
         rc.ElapseFromBegin("do search");
 
-        //step 5: construct result array
+        //step 7: construct result array
         for (uint64_t i = 0; i < record_count; i++) {
             auto &result = results[i];
             const auto &record = search_param_->query_record_array(i);
@@ -699,10 +704,10 @@ SearchTask::OnExecute() {
         ProfilerStop();
 #endif
 
+        //step 8: print time cost percent
         double span_result = rc.RecordSection("construct result");
         rc.ElapseFromBegin("totally cost");
 
-        //step 6: print time cost percent
 
     } catch (std::exception &ex) {
         return SetError(SERVER_UNEXPECTED_ERROR, ex.what());
@@ -740,7 +745,7 @@ CountTableTask::OnExecute() {
         uint64_t row_count = 0;
         engine::Status stat = DBWrapper::DB()->GetTableRowCount(table_name_, row_count);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         row_count_ = (int64_t) row_count;
@@ -816,7 +821,7 @@ DeleteByRangeTask::OnExecute() {
             if (stat.IsNotFound()) {
                 return SetError(SERVER_TABLE_NOT_EXIST, "Table " + table_name + " not exists");
             } else {
-                return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+                return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
             }
         }
 
@@ -842,7 +847,7 @@ DeleteByRangeTask::OnExecute() {
 #endif
         engine::Status status = DBWrapper::DB()->DeleteTable(table_name, dates);
         if (!status.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
     } catch (std::exception &ex) {
@@ -878,7 +883,7 @@ PreloadTableTask::OnExecute() {
         //step 2: check table existence
         engine::Status stat = DBWrapper::DB()->PreloadTable(table_name_);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         rc.ElapseFromBegin("totally cost");
@@ -919,7 +924,7 @@ DescribeIndexTask::OnExecute() {
         engine::TableIndex index;
         engine::Status stat = DBWrapper::DB()->DescribeIndex(table_name_, index);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         index_param_->mutable_table_name()->set_table_name(table_name_);
@@ -961,7 +966,7 @@ DropIndexTask::OnExecute() {
         //step 2: check table existence
         engine::Status stat = DBWrapper::DB()->DropIndex(table_name_);
         if (!stat.ok()) {
-            return SetError(DB_META_TRANSACTION_FAILED, "Engine failed: " + stat.ToString());
+            return SetError(DB_META_TRANSACTION_FAILED, stat.ToString());
         }
 
         rc.ElapseFromBegin("totally cost");
diff --git a/cpp/src/utils/ValidationUtil.cpp b/cpp/src/utils/ValidationUtil.cpp
index 0e2e1c2b4f0dfffeb88cb94ac7704930b14859ac..2245496903aca085b8d28bfc10afe93c902c7506 100644
--- a/cpp/src/utils/ValidationUtil.cpp
+++ b/cpp/src/utils/ValidationUtil.cpp
@@ -92,6 +92,24 @@ ValidationUtil::ValidateTableIndexMetricType(int32_t metric_type) {
     return SERVER_SUCCESS;
 }
 
+ServerError
+ValidationUtil::ValidateSearchTopk(int64_t top_k, const engine::meta::TableSchema& table_schema) {
+    if (top_k <= 0 || top_k > 1024) {
+        return SERVER_INVALID_TOPK;
+    }
+
+    return SERVER_SUCCESS;
+}
+
+ServerError
+ValidationUtil::ValidateSearchNprobe(int64_t nprobe, const engine::meta::TableSchema& table_schema) {
+    if (nprobe <= 0 || nprobe > table_schema.nlist_) {
+        return SERVER_INVALID_NPROBE;
+    }
+
+    return SERVER_SUCCESS;
+}
+
 ServerError
 ValidationUtil::ValidateGpuIndex(uint32_t gpu_index) {
     int num_devices = 0;
diff --git a/cpp/src/utils/ValidationUtil.h b/cpp/src/utils/ValidationUtil.h
index 4792500f6719089e49b447f65b1b84f95f1d4a6a..d1d84f710465a6111d093c8953dd95cb8c08256a 100644
--- a/cpp/src/utils/ValidationUtil.h
+++ b/cpp/src/utils/ValidationUtil.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "db/meta/MetaTypes.h"
 #include "Error.h"
 
 namespace zilliz {
@@ -26,6 +27,12 @@ public:
     static ServerError
     ValidateTableIndexMetricType(int32_t metric_type);
 
+    static ServerError
+    ValidateSearchTopk(int64_t top_k, const engine::meta::TableSchema& table_schema);
+
+    static ServerError
+    ValidateSearchNprobe(int64_t nprobe, const engine::meta::TableSchema& table_schema);
+
     static ServerError
     ValidateGpuIndex(uint32_t gpu_index);
 
diff --git a/cpp/unittest/db/db_tests.cpp b/cpp/unittest/db/db_tests.cpp
index 668f5b512ae0fafcc762a973d8db7080eba4064d..be8748ce5cffc8465dfd3b882c772fc94942bf5d 100644
--- a/cpp/unittest/db/db_tests.cpp
+++ b/cpp/unittest/db/db_tests.cpp
@@ -34,7 +34,6 @@ namespace {
         engine::meta::TableSchema table_info;
         table_info.dimension_ = TABLE_DIM;
         table_info.table_id_ = TABLE_NAME;
-        table_info.engine_type_ = (int)engine::EngineType::FAISS_IDMAP;
         return table_info;
     }
 
@@ -263,7 +262,9 @@ TEST_F(DBTest, SEARCH_TEST) {
         ASSERT_STATS(stat);
     }
 
-    db_->BuildIndex(TABLE_NAME); // wait until build index finish
+    engine::TableIndex index;
+    index.engine_type_ = (int)engine::EngineType::FAISS_IDMAP;
+    db_->CreateIndex(TABLE_NAME, index); // wait until build index finish
 
     {
         engine::QueryResults results;
@@ -273,7 +274,7 @@ TEST_F(DBTest, SEARCH_TEST) {
 
     {//search by specify index file
         engine::meta::DatesT dates;
-        std::vector<std::string> file_ids = {"4", "5", "6"};
+        std::vector<std::string> file_ids = {"1", "2", "3", "4", "5", "6"};
         engine::QueryResults results;
         stat = db_->Query(TABLE_NAME, file_ids, k, nq, 10, xq.data(), dates, results);
         ASSERT_STATS(stat);
@@ -305,7 +306,12 @@ TEST_F(DBTest, PRELOADTABLE_TEST) {
         db_->InsertVectors(TABLE_NAME, nb, xb.data(), target_ids);
         ASSERT_EQ(target_ids.size(), nb);
     }
-    db_->BuildIndex(TABLE_NAME);
+
+    sleep(2);
+
+    engine::TableIndex index;
+    index.engine_type_ = (int)engine::EngineType::FAISS_IDMAP;
+    db_->CreateIndex(TABLE_NAME, index); // wait until build index finish
 
     int64_t prev_cache_usage = cache::CpuCacheMgr::GetInstance()->CacheUsage();
     stat = db_->PreloadTable(TABLE_NAME);
diff --git a/cpp/unittest/server/util_test.cpp b/cpp/unittest/server/util_test.cpp
index c0b1c83cf8a505db9d62d4c11b6519e49e86ada3..290655f565547a53077ffdbae5b9483101ed4c09 100644
--- a/cpp/unittest/server/util_test.cpp
+++ b/cpp/unittest/server/util_test.cpp
@@ -217,6 +217,21 @@ TEST(UtilTest, VALIDATE_INDEX_TEST) {
     ASSERT_EQ(server::ValidationUtil::ValidateTableIndexMetricType(2), server::SERVER_SUCCESS);
 }
 
+TEST(ValidationUtilTest, ValidateTopkTest) {
+    engine::meta::TableSchema schema;
+    ASSERT_EQ(server::ValidationUtil::ValidateSearchTopk(10, schema), server::SERVER_SUCCESS);
+    ASSERT_NE(server::ValidationUtil::ValidateSearchTopk(65536, schema), server::SERVER_SUCCESS);
+    ASSERT_NE(server::ValidationUtil::ValidateSearchTopk(0, schema), server::SERVER_SUCCESS);
+}
+
+TEST(ValidationUtilTest, ValidateNprobeTest) {
+    engine::meta::TableSchema schema;
+    schema.nlist_ = 100;
+    ASSERT_EQ(server::ValidationUtil::ValidateSearchNprobe(10, schema), server::SERVER_SUCCESS);
+    ASSERT_NE(server::ValidationUtil::ValidateSearchNprobe(0, schema), server::SERVER_SUCCESS);
+    ASSERT_NE(server::ValidationUtil::ValidateSearchNprobe(101, schema), server::SERVER_SUCCESS);
+}
+
 TEST(ValidationUtilTest, ValidateGpuTest) {
     ASSERT_EQ(server::ValidationUtil::ValidateGpuIndex(0), server::SERVER_SUCCESS);
     ASSERT_NE(server::ValidationUtil::ValidateGpuIndex(100), server::SERVER_SUCCESS);