MySQLMetaImpl.cpp

/*******************************************************************************
 * 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 "MySQLMetaImpl.h"
#include "db/IDGenerator.h"
#include "db/Utils.h"
#include "db/Log.h"
#include "MetaConsts.h"
#include "db/Factories.h"
#include "metrics/Metrics.h"

#include <unistd.h>
#include <sstream>
#include <iostream>
#include <boost/filesystem.hpp>
#include <chrono>
#include <fstream>
#include <regex>
#include <string>
#include <mutex>
#include <thread>

#include "mysql++/mysql++.h"


namespace zilliz {
namespace milvus {
namespace engine {
namespace meta {

using namespace mysqlpp;

namespace {

Status HandleException(const std::string &desc, std::exception &e) {
    ENGINE_LOG_ERROR << desc << ": " << e.what();
    return Status::DBTransactionError(desc, e.what());
}

}

Status MySQLMetaImpl::NextTableId(std::string &table_id) {
    std::stringstream ss;
    SimpleIDGenerator g;
    ss << g.GetNextIDNumber();
    table_id = ss.str();
    return Status::OK();
}

Status MySQLMetaImpl::NextFileId(std::string &file_id) {
    std::stringstream ss;
    SimpleIDGenerator g;
    ss << g.GetNextIDNumber();
    file_id = ss.str();
    return Status::OK();
}

MySQLMetaImpl::MySQLMetaImpl(const DBMetaOptions &options_, const int &mode)
    : options_(options_),
      mode_(mode) {
    Initialize();
}

Status MySQLMetaImpl::Initialize() {
    if (!boost::filesystem::is_directory(options_.path)) {
        auto ret = boost::filesystem::create_directory(options_.path);
        if (!ret) {
            ENGINE_LOG_ERROR << "Failed to create db directory " << options_.path;
            return Status::DBTransactionError("Failed to create db directory", options_.path);
        }
    }

    std::string uri = options_.backend_uri;

    std::string dialectRegex = "(.*)";
    std::string usernameRegex = "(.*)";
    std::string passwordRegex = "(.*)";
    std::string hostRegex = "(.*)";
    std::string portRegex = "(.*)";
    std::string dbNameRegex = "(.*)";
    std::string uriRegexStr = dialectRegex + "\\:\\/\\/" +
        usernameRegex + "\\:" +
        passwordRegex + "\\@" +
        hostRegex + "\\:" +
        portRegex + "\\/" +
        dbNameRegex;
    std::regex uriRegex(uriRegexStr);
    std::smatch pieces_match;

    if (std::regex_match(uri, pieces_match, uriRegex)) {
        std::string dialect = pieces_match[1].str();
        std::transform(dialect.begin(), dialect.end(), dialect.begin(), ::tolower);
        if (dialect.find("mysql") == std::string::npos) {
            return Status::Error("URI's dialect is not MySQL");
        }
        std::string username = pieces_match[2].str();
        std::string password = pieces_match[3].str();
        std::string serverAddress = pieces_match[4].str();
        unsigned int port = 0;
        if (!pieces_match[5].str().empty()) {
            port = std::stoi(pieces_match[5].str());
        }
        std::string dbName = pieces_match[6].str();


        int threadHint = std::thread::hardware_concurrency();
        int maxPoolSize = threadHint == 0 ? 8 : threadHint;
        mysql_connection_pool_ =
            std::make_shared<MySQLConnectionPool>(dbName, username, password, serverAddress, port, maxPoolSize);

        ENGINE_LOG_DEBUG << "MySQL connection pool: maximum pool size = " << std::to_string(maxPoolSize);
        try {

            if (mode_ != Options::MODE::READ_ONLY) {
                CleanUp();
            }

            {
                ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

                if (connectionPtr == nullptr) {
                    return Status::Error("Failed to connect to database server");
                }


                if (!connectionPtr->thread_aware()) {
                    ENGINE_LOG_ERROR << "MySQL++ wasn't built with thread awareness! Can't run without it.";
                    return Status::Error("MySQL++ wasn't built with thread awareness! Can't run without it.");
                }
                Query InitializeQuery = connectionPtr->query();

                InitializeQuery << "CREATE TABLE IF NOT EXISTS Tables (" <<
                                "id BIGINT PRIMARY KEY AUTO_INCREMENT, " <<
                                "table_id VARCHAR(255) UNIQUE NOT NULL, " <<
                                "state INT NOT NULL, " <<
                                "dimension SMALLINT NOT NULL, " <<
                                "created_on BIGINT NOT NULL, " <<
                                "flag BIGINT DEFAULT 0 NOT NULL, " <<
                                "index_file_size INT DEFAULT 1024 NOT NULL, " <<
                                "engine_type INT DEFAULT 1 NOT NULL, " <<
                                "nlist INT DEFAULT 16384 NOT NULL, " <<
                                "metric_type INT DEFAULT 1 NOT NULL);";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::Initialize: " << InitializeQuery.str();

                if (!InitializeQuery.exec()) {
                    return Status::DBTransactionError("Initialization Error", InitializeQuery.error());
                }

                InitializeQuery << "CREATE TABLE IF NOT EXISTS TableFiles (" <<
                                "id BIGINT PRIMARY KEY AUTO_INCREMENT, " <<
                                "table_id VARCHAR(255) NOT NULL, " <<
                                "engine_type INT DEFAULT 1 NOT NULL, " <<
                                "file_id VARCHAR(255) NOT NULL, " <<
                                "file_type INT DEFAULT 0 NOT NULL, " <<
                                "file_size BIGINT DEFAULT 0 NOT NULL, " <<
                                "row_count BIGINT DEFAULT 0 NOT NULL, " <<
                                "updated_time BIGINT NOT NULL, " <<
                                "created_on BIGINT NOT NULL, " <<
                                "date INT DEFAULT -1 NOT NULL);";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::Initialize: " << InitializeQuery.str();

                if (!InitializeQuery.exec()) {
                    return Status::DBTransactionError("Initialization Error", InitializeQuery.error());
                }
            } //Scoped Connection

        } catch (const BadQuery &er) {
            // Handle any query errors
            ENGINE_LOG_ERROR << "QUERY ERROR DURING INITIALIZATION" << ": " << er.what();
            return Status::DBTransactionError("QUERY ERROR DURING INITIALIZATION", er.what());
        } catch (const Exception &er) {
            // Catch-all for any other MySQL++ exceptions
            ENGINE_LOG_ERROR << "GENERAL ERROR DURING INITIALIZATION" << ": " << er.what();
            return Status::DBTransactionError("GENERAL ERROR DURING INITIALIZATION", er.what());
        } catch (std::exception &e) {
            return HandleException("Encounter exception during initialization", e);
        }
    } else {
        ENGINE_LOG_ERROR << "Wrong URI format. URI = " << uri;
        return Status::Error("Wrong URI format");
    }

    return Status::OK();
}

// PXU TODO: Temp solution. Will fix later
Status MySQLMetaImpl::DropPartitionsByDates(const std::string &table_id,
                                            const DatesT &dates) {
    if (dates.empty()) {
        return Status::OK();
    }

    TableSchema table_schema;
    table_schema.table_id_ = table_id;
    auto status = DescribeTable(table_schema);
    if (!status.ok()) {
        return status;
    }

    try {

        auto yesterday = GetDateWithDelta(-1);

        for (auto &date : dates) {
            if (date >= yesterday) {
                return Status::Error("Could not delete partitions within 2 days");
            }
        }

        std::stringstream dateListSS;
        for (auto &date : dates) {
            dateListSS << std::to_string(date) << ", ";
        }
        std::string dateListStr = dateListSS.str();
        dateListStr = dateListStr.substr(0, dateListStr.size() - 2); //remove the last ", "

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }


            Query dropPartitionsByDatesQuery = connectionPtr->query();

            dropPartitionsByDatesQuery << "UPDATE TableFiles " <<
                                       "SET file_type = " << std::to_string(TableFileSchema::TO_DELETE) << " " <<
                                       "WHERE table_id = " << quote << table_id << " AND " <<
                                       "date in (" << dateListStr << ");";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DropPartitionsByDates: " << dropPartitionsByDatesQuery.str();

            if (!dropPartitionsByDatesQuery.exec()) {
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN DROPPING PARTITIONS BY DATES";
                return Status::DBTransactionError("QUERY ERROR WHEN DROPPING PARTITIONS BY DATES",
                                                  dropPartitionsByDatesQuery.error());
            }
        } //Scoped Connection
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DROPPING PARTITIONS BY DATES" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DROPPING PARTITIONS BY DATES", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DROPPING PARTITIONS BY DATES" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DROPPING PARTITIONS BY DATES", er.what());
    }
    return Status::OK();
}

Status MySQLMetaImpl::CreateTable(TableSchema &table_schema) {
    try {
        server::MetricCollector metric;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query createTableQuery = connectionPtr->query();

            if (table_schema.table_id_.empty()) {
                NextTableId(table_schema.table_id_);
            } else {
                createTableQuery << "SELECT state FROM Tables " <<
                                 "WHERE table_id = " << quote << table_schema.table_id_ << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::CreateTable: " << createTableQuery.str();

                StoreQueryResult res = createTableQuery.store();

                if (res.num_rows() == 1) {
                    int state = res[0]["state"];
                    if (TableSchema::TO_DELETE == state) {
                        return Status::Error("Table already exists and it is in delete state, please wait a second");
                    } else {
                        return Status::AlreadyExist("Table already exists");
                    }
                }
            }

            table_schema.id_ = -1;
            table_schema.created_on_ = utils::GetMicroSecTimeStamp();

            std::string id = "NULL"; //auto-increment
            std::string table_id = table_schema.table_id_;
            std::string state = std::to_string(table_schema.state_);
            std::string dimension = std::to_string(table_schema.dimension_);
            std::string created_on = std::to_string(table_schema.created_on_);
            std::string engine_type = std::to_string(table_schema.engine_type_);

            createTableQuery << "INSERT INTO Tables VALUES" <<
                             "(" << id << ", " << quote << table_id << ", " << state << ", " << dimension << ", " <<
                             created_on << ", " << engine_type << ");";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::CreateTable: " << createTableQuery.str();

            if (SimpleResult res = createTableQuery.execute()) {
                table_schema.id_ = res.insert_id(); //Might need to use SELECT LAST_INSERT_ID()?

                //Consume all results to avoid "Commands out of sync" error
            } else {
                ENGINE_LOG_ERROR << "Add Table Error";
                return Status::DBTransactionError("Add Table Error", createTableQuery.error());
            }
        } //Scoped Connection

        return utils::CreateTablePath(options_, table_schema.table_id_);

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN ADDING TABLE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN ADDING TABLE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN ADDING TABLE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN ADDING TABLE", er.what());
    } catch (std::exception &e) {
        return HandleException("Encounter exception when create table", e);
    }
}

Status MySQLMetaImpl::HasNonIndexFiles(const std::string &table_id, bool &has) {
    has = false;

    try {
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query hasNonIndexFilesQuery = connectionPtr->query();
            //since table_id is a unique column we just need to check whether it exists or not
            hasNonIndexFilesQuery << "SELECT EXISTS " <<
                                  "(SELECT 1 FROM TableFiles " <<
                                  "WHERE table_id = " << quote << table_id << " AND " <<
                                  "(file_type = " << std::to_string(TableFileSchema::RAW) << " OR " <<
                                  "file_type = " << std::to_string(TableFileSchema::NEW) << " OR " <<
                                  "file_type = " << std::to_string(TableFileSchema::NEW_MERGE) << " OR " <<
                                  "file_type = " << std::to_string(TableFileSchema::NEW_INDEX) << " OR " <<
                                  "file_type = " << std::to_string(TableFileSchema::TO_INDEX) << ")) " <<
                                  "AS " << quote << "check" << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::HasNonIndexFiles: " << hasNonIndexFilesQuery.str();

            res = hasNonIndexFilesQuery.store();
        } //Scoped Connection

        int check = res[0]["check"];
        has = (check == 1);

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN CHECKING IF NON INDEX FILES EXISTS" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN CHECKING IF NON INDEX FILES EXISTS", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN CHECKING IF NON INDEX FILES EXISTS" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN CHECKING IF NON INDEX FILES EXISTS", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::UpdateTableIndexParam(const std::string &table_id, const TableIndex& index) {
    try {
        server::MetricCollector metric;

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query updateTableIndexParamQuery = connectionPtr->query();
            updateTableIndexParamQuery << "SELECT id, state, dimension, created_on " <<
                                       "FROM Tables " <<
                                       "WHERE table_id = " << quote << table_id << " AND " <<
                                       "state <> " << std::to_string(TableSchema::TO_DELETE) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableIndexParam: " << updateTableIndexParamQuery.str();

            StoreQueryResult res = updateTableIndexParamQuery.store();

            if (res.num_rows() == 1) {
                const Row &resRow = res[0];

                size_t id = resRow["id"];
                int32_t state = resRow["state"];
                uint16_t dimension = resRow["dimension"];
                int64_t created_on = resRow["created_on"];

                updateTableIndexParamQuery << "UPDATE Tables " <<
                                           "SET id = " << id << ", " <<
                                           "state = " << state << ", " <<
                                           "dimension = " << dimension << ", " <<
                                           "created_on = " << created_on << ", " <<
                                           "engine_type_ = " << index.engine_type_ << ", " <<
                                           "nlist = " << index.nlist_ << ", " <<
                                           "metric_type = " << index.metric_type_ << " " <<
                                           "WHERE id = " << quote << table_id << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableIndexParam: " << updateTableIndexParamQuery.str();


                if (!updateTableIndexParamQuery.exec()) {
                    ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE INDEX PARAM";
                    return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE INDEX PARAM",
                                                      updateTableIndexParamQuery.error());
                }
            } else {
                return Status::NotFound("Table " + table_id + " not found");
            }

        } //Scoped Connection

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE INDEX PARAM" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE INDEX PARAM", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN UPDATING TABLE INDEX PARAM" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN UPDATING TABLE INDEX PARAM", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::UpdateTableFlag(const std::string &table_id, int64_t flag) {
    try {
        server::MetricCollector metric;

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query updateTableFlagQuery = connectionPtr->query();
            updateTableFlagQuery << "UPDATE Tables " <<
                                 "SET flag = " << flag << " " <<
                                 "WHERE id = " << quote << table_id << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableFlag: " << updateTableFlagQuery.str();


            if (!updateTableFlagQuery.exec()) {
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FLAG";
                return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FLAG",
                                                  updateTableFlagQuery.error());
            }

        } //Scoped Connection

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FLAG" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FLAG", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN UPDATING TABLE FLAG" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN UPDATING TABLE FLAG", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::DescribeTableIndex(const std::string &table_id, TableIndex& index) {
    try {
        server::MetricCollector metric;

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query describeTableIndexQuery = connectionPtr->query();
            describeTableIndexQuery << "SELECT engine_type, nlist, index_file_size, metric_type " <<
                                       "FROM Tables " <<
                                       "WHERE table_id = " << quote << table_id << " AND " <<
                                       "state <> " << std::to_string(TableSchema::TO_DELETE) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DescribeTableIndex: " << describeTableIndexQuery.str();

            StoreQueryResult res = describeTableIndexQuery.store();

            if (res.num_rows() == 1) {
                const Row &resRow = res[0];

                index.engine_type_ = resRow["engine_type"];
                index.nlist_ = resRow["nlist"];
                index.metric_type_ = resRow["metric_type"];
            } else {
                return Status::NotFound("Table " + table_id + " not found");
            }

        } //Scoped Connection

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DESCRIBE TABLE INDEX" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DESCRIBE TABLE INDEX", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DESCRIBE TABLE INDEX" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DESCRIBE TABLE INDEX", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::DropTableIndex(const std::string &table_id) {
    try {
        server::MetricCollector metric;

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query dropTableIndexQuery = connectionPtr->query();

            //soft delete index files
            dropTableIndexQuery << "UPDATE TableFiles " <<
                                "SET file_type = " << std::to_string(TableFileSchema::TO_DELETE) << "," <<
                                "updated_time = " << utils::GetMicroSecTimeStamp() << " " <<
                                "WHERE table_id = " << quote << table_id << " AND " <<
                                "file_type = " << std::to_string(TableFileSchema::INDEX) << ";";

            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());
            }

            //set all backup file to raw
            dropTableIndexQuery << "UPDATE TableFiles " <<
                                "SET file_type = " << std::to_string(TableFileSchema::RAW) << "," <<
                                "updated_time = " << utils::GetMicroSecTimeStamp() << " " <<
                                "WHERE table_id = " << quote << table_id << " AND " <<
                                "file_type = " << std::to_string(TableFileSchema::BACKUP) << ";";

            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());
            }

            //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) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DROP TABLE INDEX" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DROP TABLE INDEX", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DROP TABLE INDEX" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DROP TABLE INDEX", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::DeleteTable(const std::string &table_id) {
    try {
        server::MetricCollector metric;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            //soft delete table
            Query deleteTableQuery = connectionPtr->query();
//
            deleteTableQuery << "UPDATE Tables " <<
                             "SET state = " << std::to_string(TableSchema::TO_DELETE) << " " <<
                             "WHERE table_id = " << quote << table_id << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DeleteTable: " << deleteTableQuery.str();

            if (!deleteTableQuery.exec()) {
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN DELETING TABLE";
                return Status::DBTransactionError("QUERY ERROR WHEN DELETING TABLE", deleteTableQuery.error());
            }

        } //Scoped Connection

        if (mode_ == Options::MODE::CLUSTER) {
            DeleteTableFiles(table_id);
        }

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DELETING TABLE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DELETING TABLE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DELETING TABLE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DELETING TABLE", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::DeleteTableFiles(const std::string &table_id) {
    try {
        server::MetricCollector metric;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            //soft delete table files
            Query deleteTableFilesQuery = connectionPtr->query();
            //
            deleteTableFilesQuery << "UPDATE TableFiles " <<
                                  "SET file_type = " << std::to_string(TableFileSchema::TO_DELETE) << ", " <<
                                  "updated_time = " << std::to_string(utils::GetMicroSecTimeStamp()) << " " <<
                                  "WHERE table_id = " << quote << table_id << " AND " <<
                                  "file_type <> " << std::to_string(TableFileSchema::TO_DELETE) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DeleteTableFiles: " << deleteTableFilesQuery.str();

            if (!deleteTableFilesQuery.exec()) {
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN DELETING TABLE FILES";
                return Status::DBTransactionError("QUERY ERROR WHEN DELETING TABLE", deleteTableFilesQuery.error());
            }
        } //Scoped Connection
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DELETING TABLE FILES" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DELETING TABLE FILES", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DELETING TABLE FILES" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DELETING TABLE FILES", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::DescribeTable(TableSchema &table_schema) {
    try {
        server::MetricCollector metric;
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query describeTableQuery = connectionPtr->query();
            describeTableQuery << "SELECT id, state, dimension, engine_type, nlist, index_file_size, metric_type " <<
                               "FROM Tables " <<
                               "WHERE table_id = " << quote << table_schema.table_id_ << " " <<
                               "AND state <> " << std::to_string(TableSchema::TO_DELETE) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DescribeTable: " << describeTableQuery.str();

            res = describeTableQuery.store();
        } //Scoped Connection

        if (res.num_rows() == 1) {
            const Row &resRow = res[0];

            table_schema.id_ = resRow["id"]; //implicit conversion

            table_schema.state_ = resRow["state"];

            table_schema.dimension_ = resRow["dimension"];

            table_schema.index_file_size_ = resRow["index_file_size"];

            table_schema.engine_type_ = resRow["engine_type"];

            table_schema.nlist_ = resRow["nlist"];

            table_schema.metric_type_ = resRow["metric_type"];
        } else {
            return Status::NotFound("Table " + table_schema.table_id_ + " not found");
        }

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DESCRIBING TABLE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DESCRIBING TABLE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DESCRIBING TABLE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DESCRIBING TABLE", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::HasTable(const std::string &table_id, bool &has_or_not) {
    try {
        server::MetricCollector metric;
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query hasTableQuery = connectionPtr->query();
            //since table_id is a unique column we just need to check whether it exists or not
            hasTableQuery << "SELECT EXISTS " <<
                          "(SELECT 1 FROM Tables " <<
                          "WHERE table_id = " << quote << table_id << " " <<
                          "AND state <> " << std::to_string(TableSchema::TO_DELETE) << ") " <<
                          "AS " << quote << "check" << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::HasTable: " << hasTableQuery.str();

            res = hasTableQuery.store();
        } //Scoped Connection

        int check = res[0]["check"];
        has_or_not = (check == 1);

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN CHECKING IF TABLE EXISTS" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN CHECKING IF TABLE EXISTS", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN CHECKING IF TABLE EXISTS" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN CHECKING IF TABLE EXISTS", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::AllTables(std::vector<TableSchema> &table_schema_array) {
    try {
        server::MetricCollector metric;
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query allTablesQuery = connectionPtr->query();
            allTablesQuery << "SELECT id, table_id, dimension, engine_type, nlist, index_file_size, metric_type " <<
                           "FROM Tables " <<
                           "WHERE state <> " << std::to_string(TableSchema::TO_DELETE) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::AllTables: " << allTablesQuery.str();

            res = allTablesQuery.store();
        } //Scoped Connection

        for (auto &resRow : res) {
            TableSchema table_schema;

            table_schema.id_ = resRow["id"]; //implicit conversion

            std::string table_id;
            resRow["table_id"].to_string(table_id);
            table_schema.table_id_ = table_id;

            table_schema.dimension_ = resRow["dimension"];

            table_schema.index_file_size_ = resRow["index_file_size"];

            table_schema.engine_type_ = resRow["engine_type"];

            table_schema.nlist_ = resRow["nlist"];

            table_schema.metric_type_ = resRow["metric_type"];

            table_schema_array.emplace_back(table_schema);
        }
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DESCRIBING ALL TABLES" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DESCRIBING ALL TABLES", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DESCRIBING ALL TABLES" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DESCRIBING ALL TABLES", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::CreateTableFile(TableFileSchema &file_schema) {
    if (file_schema.date_ == EmptyDate) {
        file_schema.date_ = Meta::GetDate();
    }
    TableSchema table_schema;
    table_schema.table_id_ = file_schema.table_id_;
    auto status = DescribeTable(table_schema);
    if (!status.ok()) {
        return status;
    }

    try {
        server::MetricCollector metric;

        NextFileId(file_schema.file_id_);
        file_schema.dimension_ = table_schema.dimension_;
        file_schema.file_size_ = 0;
        file_schema.row_count_ = 0;
        file_schema.created_on_ = utils::GetMicroSecTimeStamp();
        file_schema.updated_time_ = file_schema.created_on_;
        file_schema.index_file_size_ = table_schema.index_file_size_;
        file_schema.engine_type_ = table_schema.engine_type_;
        file_schema.nlist_ = table_schema.nlist_;
        file_schema.metric_type_ = table_schema.metric_type_;
        utils::GetTableFilePath(options_, file_schema);

        std::string id = "NULL"; //auto-increment
        std::string table_id = file_schema.table_id_;
        std::string engine_type = std::to_string(file_schema.engine_type_);
        std::string file_id = file_schema.file_id_;
        std::string file_type = std::to_string(file_schema.file_type_);
        std::string row_count = std::to_string(file_schema.row_count_);
        std::string updated_time = std::to_string(file_schema.updated_time_);
        std::string created_on = std::to_string(file_schema.created_on_);
        std::string date = std::to_string(file_schema.date_);

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query createTableFileQuery = connectionPtr->query();

            createTableFileQuery << "INSERT INTO TableFiles VALUES" <<
                                 "(" << id << ", " << quote << table_id << ", " << engine_type << ", " <<
                                 quote << file_id << ", " << file_type << ", " << row_count << ", " <<
                                 updated_time << ", " << created_on << ", " << date << ");";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::CreateTableFile: " << createTableFileQuery.str();

            if (SimpleResult res = createTableFileQuery.execute()) {
                file_schema.id_ = res.insert_id(); //Might need to use SELECT LAST_INSERT_ID()?

                //Consume all results to avoid "Commands out of sync" error
            } else {
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN ADDING TABLE FILE";
                return Status::DBTransactionError("Add file Error", createTableFileQuery.error());
            }
        } // Scoped Connection

        return utils::CreateTableFilePath(options_, file_schema);

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN ADDING TABLE FILE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN ADDING TABLE FILE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN ADDING TABLE FILE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN ADDING TABLE FILE", er.what());
    } catch (std::exception &ex) {
        return HandleException("Encounter exception when create table file", ex);
    }
}

Status MySQLMetaImpl::FilesToIndex(TableFilesSchema &files) {
    files.clear();

    try {
        server::MetricCollector metric;
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query filesToIndexQuery = connectionPtr->query();
            filesToIndexQuery << "SELECT id, table_id, engine_type, file_id, file_type, file_size, row_count, date, created_on " <<
                              "FROM TableFiles " <<
                              "WHERE file_type = " << std::to_string(TableFileSchema::TO_INDEX) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::FilesToIndex: " << filesToIndexQuery.str();

            res = filesToIndexQuery.store();
        } //Scoped Connection

        std::map<std::string, TableSchema> groups;
        TableFileSchema table_file;
        for (auto &resRow : res) {

            table_file.id_ = resRow["id"]; //implicit conversion

            std::string table_id;
            resRow["table_id"].to_string(table_id);
            table_file.table_id_ = table_id;

            table_file.engine_type_ = resRow["engine_type"];

            std::string file_id;
            resRow["file_id"].to_string(file_id);
            table_file.file_id_ = file_id;

            table_file.file_type_ = resRow["file_type"];

            table_file.file_size_ = resRow["file_size"];

            table_file.row_count_ = resRow["row_count"];

            table_file.date_ = resRow["date"];

            table_file.created_on_ = resRow["created_on"];

            auto groupItr = groups.find(table_file.table_id_);
            if (groupItr == groups.end()) {
                TableSchema table_schema;
                table_schema.table_id_ = table_file.table_id_;
                auto status = DescribeTable(table_schema);
                if (!status.ok()) {
                    return status;
                }
                groups[table_file.table_id_] = table_schema;

            }
            table_file.dimension_ = groups[table_file.table_id_].dimension_;
            table_file.index_file_size_ = groups[table_file.table_id_].index_file_size_;
            table_file.nlist_ = groups[table_file.table_id_].nlist_;
            table_file.metric_type_ = groups[table_file.table_id_].metric_type_;

            utils::GetTableFilePath(options_, table_file);

            files.push_back(table_file);
        }
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN FINDING TABLE FILES TO INDEX" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN FINDING TABLE FILES TO INDEX", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN FINDING TABLE FILES TO INDEX" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN FINDING TABLE FILES TO INDEX", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::FilesToSearch(const std::string &table_id,
                                    const DatesT &partition,
                                    DatePartionedTableFilesSchema &files) {
    files.clear();

    try {
        server::MetricCollector metric;
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            if (partition.empty()) {

                Query filesToSearchQuery = connectionPtr->query();
                filesToSearchQuery << "SELECT id, table_id, engine_type, file_id, file_type, file_size, row_count, date " <<
                                   "FROM TableFiles " <<
                                   "WHERE table_id = " << quote << table_id << " AND " <<
                                   "(file_type = " << std::to_string(TableFileSchema::RAW) << " OR " <<
                                   "file_type = " << std::to_string(TableFileSchema::TO_INDEX) << " OR " <<
                                   "file_type = " << std::to_string(TableFileSchema::INDEX) << ");";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::FilesToSearch: " << filesToSearchQuery.str();

                res = filesToSearchQuery.store();

            } else {

                Query filesToSearchQuery = connectionPtr->query();

                std::stringstream partitionListSS;
                for (auto &date : partition) {
                    partitionListSS << std::to_string(date) << ", ";
                }
                std::string partitionListStr = partitionListSS.str();
                partitionListStr = partitionListStr.substr(0, partitionListStr.size() - 2); //remove the last ", "

                filesToSearchQuery << "SELECT id, table_id, engine_type, file_id, file_type, file_size, row_count, date " <<
                                   "FROM TableFiles " <<
                                   "WHERE table_id = " << quote << table_id << " AND " <<
                                   "date IN (" << partitionListStr << ") AND " <<
                                   "(file_type = " << std::to_string(TableFileSchema::RAW) << " OR " <<
                                   "file_type = " << std::to_string(TableFileSchema::TO_INDEX) << " OR " <<
                                   "file_type = " << std::to_string(TableFileSchema::INDEX) << ");";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::FilesToSearch: " << filesToSearchQuery.str();

                res = filesToSearchQuery.store();

            }
        } //Scoped Connection

        TableSchema table_schema;
        table_schema.table_id_ = table_id;
        auto status = DescribeTable(table_schema);
        if (!status.ok()) {
            return status;
        }

        TableFileSchema table_file;
        for (auto &resRow : res) {

            table_file.id_ = resRow["id"]; //implicit conversion

            std::string table_id_str;
            resRow["table_id"].to_string(table_id_str);
            table_file.table_id_ = table_id_str;

            table_file.index_file_size_ = table_schema.index_file_size_;

            table_file.engine_type_ = resRow["engine_type"];

            table_file.nlist_ = table_schema.nlist_;

            table_file.metric_type_ = table_schema.metric_type_;

            std::string file_id;
            resRow["file_id"].to_string(file_id);
            table_file.file_id_ = file_id;

            table_file.file_type_ = resRow["file_type"];

            table_file.file_size_ = resRow["file_size"];

            table_file.row_count_ = resRow["row_count"];

            table_file.date_ = resRow["date"];

            table_file.dimension_ = table_schema.dimension_;

            utils::GetTableFilePath(options_, 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);
        }
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN FINDING TABLE FILES TO SEARCH" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN FINDING TABLE FILES TO SEARCH", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN FINDING TABLE FILES TO SEARCH" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN FINDING TABLE FILES TO SEARCH", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::FilesToSearch(const std::string &table_id,
                                    const std::vector<size_t> &ids,
                                    const DatesT &partition,
                                    DatePartionedTableFilesSchema &files) {
    files.clear();

    try {
        server::MetricCollector metric;
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query filesToSearchQuery = connectionPtr->query();
            filesToSearchQuery << "SELECT id, table_id, engine_type, file_id, file_type, file_size, row_count, date " <<
                               "FROM TableFiles " <<
                               "WHERE table_id = " << quote << table_id;

            if (!partition.empty()) {
                std::stringstream partitionListSS;
                for (auto &date : partition) {
                    partitionListSS << std::to_string(date) << ", ";
                }
                std::string partitionListStr = partitionListSS.str();

                partitionListStr = partitionListStr.substr(0, partitionListStr.size() - 2); //remove the last ", "
                filesToSearchQuery << " AND " << "date IN (" << partitionListStr << ")";
            }

            if (!ids.empty()) {
                std::stringstream idSS;
                for (auto &id : ids) {
                    idSS << "id = " << std::to_string(id) << " OR ";
                }
                std::string idStr = idSS.str();
                idStr = idStr.substr(0, idStr.size() - 4); //remove the last " OR "

                filesToSearchQuery  << " AND " << "(" << idStr << ")";

            }
            // End
            filesToSearchQuery << " AND " <<
                               "(file_type = " << std::to_string(TableFileSchema::RAW) << " OR " <<
                               "file_type = " << std::to_string(TableFileSchema::TO_INDEX) << " OR " <<
                               "file_type = " << std::to_string(TableFileSchema::INDEX) << ");";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::FilesToSearch: " << filesToSearchQuery.str();

            res = filesToSearchQuery.store();
        } //Scoped Connection

        TableSchema table_schema;
        table_schema.table_id_ = table_id;
        auto status = DescribeTable(table_schema);
        if (!status.ok()) {
            return status;
        }

        TableFileSchema table_file;
        for (auto &resRow : res) {

            table_file.id_ = resRow["id"]; //implicit conversion

            std::string table_id_str;
            resRow["table_id"].to_string(table_id_str);
            table_file.table_id_ = table_id_str;

            table_file.index_file_size_ = table_schema.index_file_size_;

            table_file.engine_type_ = resRow["engine_type"];

            table_file.nlist_ = table_schema.nlist_;

            table_file.metric_type_ = table_schema.metric_type_;

            std::string file_id;
            resRow["file_id"].to_string(file_id);
            table_file.file_id_ = file_id;

            table_file.file_type_ = resRow["file_type"];

            table_file.file_size_ = resRow["file_size"];

            table_file.row_count_ = resRow["row_count"];

            table_file.date_ = resRow["date"];

            table_file.dimension_ = table_schema.dimension_;

            utils::GetTableFilePath(options_, 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);
        }
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN FINDING TABLE FILES TO SEARCH" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN FINDING TABLE FILES TO SEARCH", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN FINDING TABLE FILES TO SEARCH" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN FINDING TABLE FILES TO SEARCH", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::FilesToMerge(const std::string &table_id,
                                   DatePartionedTableFilesSchema &files) {
    files.clear();

    try {
        server::MetricCollector metric;

        //check table existence
        TableSchema table_schema;
        table_schema.table_id_ = table_id;
        auto status = DescribeTable(table_schema);
        if (!status.ok()) {
            return status;
        }

        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query filesToMergeQuery = connectionPtr->query();
            filesToMergeQuery << "SELECT id, table_id, file_id, file_type, file_size, row_count, date, engine_type, create_on " <<
                              "FROM TableFiles " <<
                              "WHERE table_id = " << quote << table_id << " AND " <<
                              "file_type = " << std::to_string(TableFileSchema::RAW) << " " <<
                              "ORDER BY row_count DESC" << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::FilesToMerge: " << filesToMergeQuery.str();

            res = filesToMergeQuery.store();
        } //Scoped Connection

        for (auto &resRow : res) {
            TableFileSchema table_file;
            table_file.file_size_ = resRow["file_size"];
            if(table_file.file_size_ >= table_schema.index_file_size_) {
                continue;//skip large file
            }

            table_file.id_ = resRow["id"]; //implicit conversion

            std::string table_id_str;
            resRow["table_id"].to_string(table_id_str);
            table_file.table_id_ = table_id_str;

            std::string file_id;
            resRow["file_id"].to_string(file_id);
            table_file.file_id_ = file_id;

            table_file.file_type_ = resRow["file_type"];

            table_file.row_count_ = resRow["row_count"];

            table_file.date_ = resRow["date"];

            table_file.index_file_size_ = table_schema.index_file_size_;

            table_file.engine_type_ = resRow["engine_type"];

            table_file.nlist_ = table_schema.nlist_;

            table_file.metric_type_ = table_schema.metric_type_;

            table_file.created_on_ = resRow["created_on"];

            table_file.dimension_ = table_schema.dimension_;

            utils::GetTableFilePath(options_, 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);
        }

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN FINDING TABLE FILES TO MERGE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN FINDING TABLE FILES TO MERGE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN FINDING TABLE FILES TO MERGE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN FINDING TABLE FILES TO MERGE", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::GetTableFiles(const std::string &table_id,
                                    const std::vector<size_t> &ids,
                                    TableFilesSchema &table_files) {
    if (ids.empty()) {
        return Status::OK();
    }

    std::stringstream idSS;
    for (auto &id : ids) {
        idSS << "id = " << std::to_string(id) << " OR ";
    }
    std::string idStr = idSS.str();
    idStr = idStr.substr(0, idStr.size() - 4); //remove the last " OR "

    try {
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }


            Query getTableFileQuery = connectionPtr->query();
            getTableFileQuery << "SELECT id, engine_type, file_id, file_type, file_size, row_count, date, created_on " <<
                              "FROM TableFiles " <<
                              "WHERE table_id = " << quote << table_id << " AND " <<
                              "(" << idStr << ");";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::GetTableFiles: " << getTableFileQuery.str();

            res = getTableFileQuery.store();
        } //Scoped Connection

        TableSchema table_schema;
        table_schema.table_id_ = table_id;
        auto status = DescribeTable(table_schema);
        if (!status.ok()) {
            return status;
        }

        for (auto &resRow : res) {

            TableFileSchema file_schema;

            file_schema.id_ = resRow["id"];

            file_schema.table_id_ = table_id;

            file_schema.index_file_size_ = table_schema.index_file_size_;

            file_schema.engine_type_ = resRow["engine_type"];

            file_schema.nlist_ = table_schema.nlist_;

            file_schema.metric_type_ = table_schema.metric_type_;

            std::string file_id;
            resRow["file_id"].to_string(file_id);
            file_schema.file_id_ = file_id;

            file_schema.file_type_ = resRow["file_type"];

            file_schema.file_size_ = resRow["file_size"];

            file_schema.row_count_ = resRow["row_count"];

            file_schema.date_ = resRow["date"];

            file_schema.created_on_ = resRow["created_on"];

            file_schema.dimension_ = table_schema.dimension_;

            utils::GetTableFilePath(options_, file_schema);

            table_files.emplace_back(file_schema);
        }
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN RETRIEVING TABLE FILES" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN RETRIEVING TABLE FILES", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN RETRIEVING TABLE FILES" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN RETRIEVING TABLE FILES", er.what());
    }

    return Status::OK();
}

// PXU TODO: Support Swap
Status MySQLMetaImpl::Archive() {
    auto &criterias = options_.archive_conf.GetCriterias();
    if (criterias.empty()) {
        return Status::OK();
    }

    for (auto &kv : criterias) {
        auto &criteria = kv.first;
        auto &limit = kv.second;
        if (criteria == "days") {
            size_t usecs = limit * D_SEC * US_PS;
            long now = utils::GetMicroSecTimeStamp();

            try {
                ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

                if (connectionPtr == nullptr) {
                    return Status::Error("Failed to connect to database server");
                }

                Query archiveQuery = connectionPtr->query();
                archiveQuery << "UPDATE TableFiles " <<
                             "SET file_type = " << std::to_string(TableFileSchema::TO_DELETE) << " " <<
                             "WHERE created_on < " << std::to_string(now - usecs) << " AND " <<
                             "file_type <> " << std::to_string(TableFileSchema::TO_DELETE) << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::Archive: " << archiveQuery.str();

                if (!archiveQuery.exec()) {
                    return Status::DBTransactionError("QUERY ERROR DURING ARCHIVE", archiveQuery.error());
                }

            } catch (const BadQuery &er) {
                // Handle any query errors
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN DURING ARCHIVE" << ": " << er.what();
                return Status::DBTransactionError("QUERY ERROR WHEN DURING ARCHIVE", er.what());
            } catch (const Exception &er) {
                // Catch-all for any other MySQL++ exceptions
                ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DURING ARCHIVE" << ": " << er.what();
                return Status::DBTransactionError("GENERAL ERROR WHEN DURING ARCHIVE", er.what());
            }
        }
        if (criteria == "disk") {
            uint64_t sum = 0;
            Size(sum);

            auto to_delete = (sum - limit * G);
            DiscardFiles(to_delete);
        }
    }

    return Status::OK();
}

Status MySQLMetaImpl::Size(uint64_t &result) {
    result = 0;

    try {
        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }


            Query getSizeQuery = connectionPtr->query();
            getSizeQuery << "SELECT IFNULL(SUM(file_size),0) AS sum " <<
                         "FROM TableFiles " <<
                         "WHERE file_type <> " << std::to_string(TableFileSchema::TO_DELETE) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::Size: " << getSizeQuery.str();

            res = getSizeQuery.store();
        } //Scoped Connection

        if (res.empty()) {
            result = 0;
        } else {
            result = res[0]["sum"];
        }

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN RETRIEVING SIZE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN RETRIEVING SIZE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN RETRIEVING SIZE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN RETRIEVING SIZE", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::DiscardFiles(long long to_discard_size) {
    if (to_discard_size <= 0) {

        return Status::OK();
    }
    ENGINE_LOG_DEBUG << "About to discard size=" << to_discard_size;

    try {
        server::MetricCollector metric;
        bool status;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query discardFilesQuery = connectionPtr->query();
            discardFilesQuery << "SELECT id, file_size " <<
                              "FROM TableFiles " <<
                              "WHERE file_type <> " << std::to_string(TableFileSchema::TO_DELETE) << " " <<
                              "ORDER BY id ASC " <<
                              "LIMIT 10;";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DiscardFiles: " << discardFilesQuery.str();

            StoreQueryResult res = discardFilesQuery.store();
            if (res.num_rows() == 0) {
                return Status::OK();
            }

            TableFileSchema table_file;
            std::stringstream idsToDiscardSS;
            for (auto &resRow : res) {
                if (to_discard_size <= 0) {
                    break;
                }
                table_file.id_ = resRow["id"];
                table_file.file_size_ = resRow["file_size"];
                idsToDiscardSS << "id = " << std::to_string(table_file.id_) << " OR ";
                ENGINE_LOG_DEBUG << "Discard table_file.id=" << table_file.file_id_
                                 << " table_file.size=" << table_file.file_size_;
                to_discard_size -= table_file.file_size_;
            }

            std::string idsToDiscardStr = idsToDiscardSS.str();
            idsToDiscardStr = idsToDiscardStr.substr(0, idsToDiscardStr.size() - 4); //remove the last " OR "

            discardFilesQuery << "UPDATE TableFiles " <<
                              "SET file_type = " << std::to_string(TableFileSchema::TO_DELETE) << ", " <<
                              "updated_time = " << std::to_string(utils::GetMicroSecTimeStamp()) << " " <<
                              "WHERE " << idsToDiscardStr << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::DiscardFiles: " << discardFilesQuery.str();

            status = discardFilesQuery.exec();
            if (!status) {
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN DISCARDING FILES";
                return Status::DBTransactionError("QUERY ERROR WHEN DISCARDING FILES", discardFilesQuery.error());
            }
        } //Scoped Connection

        return DiscardFiles(to_discard_size);

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DISCARDING FILES" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DISCARDING FILES", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DISCARDING FILES" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DISCARDING FILES", er.what());
    }
}

//ZR: this function assumes all fields in file_schema have value
Status MySQLMetaImpl::UpdateTableFile(TableFileSchema &file_schema) {
    file_schema.updated_time_ = utils::GetMicroSecTimeStamp();

    try {
        server::MetricCollector metric;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query updateTableFileQuery = connectionPtr->query();

            //if the table has been deleted, just mark the table file as TO_DELETE
            //clean thread will delete the file later
            updateTableFileQuery << "SELECT state FROM Tables " <<
                                 "WHERE table_id = " << quote << file_schema.table_id_ << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableFile: " << updateTableFileQuery.str();

            StoreQueryResult res = updateTableFileQuery.store();

            if (res.num_rows() == 1) {
                int state = res[0]["state"];
                if (state == TableSchema::TO_DELETE) {
                    file_schema.file_type_ = TableFileSchema::TO_DELETE;
                }
            } else {
                file_schema.file_type_ = TableFileSchema::TO_DELETE;
            }

            std::string id = std::to_string(file_schema.id_);
            std::string table_id = file_schema.table_id_;
            std::string engine_type = std::to_string(file_schema.engine_type_);
            std::string file_id = file_schema.file_id_;
            std::string file_type = std::to_string(file_schema.file_type_);
            std::string file_size = std::to_string(file_schema.file_size_);
            std::string row_count = std::to_string(file_schema.row_count_);
            std::string updated_time = std::to_string(file_schema.updated_time_);
            std::string created_on = std::to_string(file_schema.created_on_);
            std::string date = std::to_string(file_schema.date_);

            updateTableFileQuery << "UPDATE TableFiles " <<
                                 "SET table_id = " << quote << table_id << ", " <<
                                 "engine_type = " << engine_type << ", " <<
                                 "file_id = " << quote << file_id << ", " <<
                                 "file_type = " << file_type << ", " <<
                                 "file_size = " << file_size << ", " <<
                                 "row_count = " << row_count << ", " <<
                                 "updated_time = " << updated_time << ", " <<
                                 "created_on = " << created_on << ", " <<
                                 "date = " << date << " " <<
                                 "WHERE id = " << id << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableFile: " << updateTableFileQuery.str();


            if (!updateTableFileQuery.exec()) {
                ENGINE_LOG_DEBUG << "table_id= " << file_schema.table_id_ << " file_id=" << file_schema.file_id_;
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FILE";
                return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FILE",
                                                  updateTableFileQuery.error());
            }
        } //Scoped Connection

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_DEBUG << "table_id= " << file_schema.table_id_ << " file_id=" << file_schema.file_id_;
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FILE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FILE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_DEBUG << "table_id= " << file_schema.table_id_ << " file_id=" << file_schema.file_id_;
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN UPDATING TABLE FILE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN UPDATING TABLE FILE", er.what());
    }
    return Status::OK();
}

Status MySQLMetaImpl::UpdateTableFilesToIndex(const std::string &table_id) {
    try {
        ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

        if (connectionPtr == nullptr) {
            return Status::Error("Failed to connect to database server");
        }

        Query updateTableFilesToIndexQuery = connectionPtr->query();

        updateTableFilesToIndexQuery << "UPDATE TableFiles " <<
                                     "SET file_type = " << std::to_string(TableFileSchema::TO_INDEX) << " " <<
                                     "WHERE table_id = " << quote << table_id << " AND " <<
                                     "file_type = " << std::to_string(TableFileSchema::RAW) << ";";

        ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableFilesToIndex: " << updateTableFilesToIndexQuery.str();

        if (!updateTableFilesToIndexQuery.exec()) {
            ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FILE";
            return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FILE",
                                              updateTableFilesToIndexQuery.error());
        }

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FILES TO INDEX" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FILES TO INDEX", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN UPDATING TABLE FILES TO INDEX" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN UPDATING TABLE FILES TO INDEX", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::UpdateTableFiles(TableFilesSchema &files) {
    try {
        server::MetricCollector metric;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query updateTableFilesQuery = connectionPtr->query();

            std::map<std::string, bool> has_tables;
            for (auto &file_schema : files) {

                if (has_tables.find(file_schema.table_id_) != has_tables.end()) {
                    continue;
                }

                updateTableFilesQuery << "SELECT EXISTS " <<
                                      "(SELECT 1 FROM Tables " <<
                                      "WHERE table_id = " << quote << file_schema.table_id_ << " " <<
                                      "AND state <> " << std::to_string(TableSchema::TO_DELETE) << ") " <<
                                      "AS " << quote << "check" << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableFiles: " << updateTableFilesQuery.str();

                StoreQueryResult res = updateTableFilesQuery.store();

                int check = res[0]["check"];
                has_tables[file_schema.table_id_] = (check == 1);
            }

            for (auto &file_schema : files) {

                if (!has_tables[file_schema.table_id_]) {
                    file_schema.file_type_ = TableFileSchema::TO_DELETE;
                }
                file_schema.updated_time_ = utils::GetMicroSecTimeStamp();

                std::string id = std::to_string(file_schema.id_);
                std::string table_id = file_schema.table_id_;
                std::string engine_type = std::to_string(file_schema.engine_type_);
                std::string file_id = file_schema.file_id_;
                std::string file_type = std::to_string(file_schema.file_type_);
                std::string file_size = std::to_string(file_schema.file_size_);
                std::string row_count = std::to_string(file_schema.row_count_);
                std::string updated_time = std::to_string(file_schema.updated_time_);
                std::string created_on = std::to_string(file_schema.created_on_);
                std::string date = std::to_string(file_schema.date_);

                updateTableFilesQuery << "UPDATE TableFiles " <<
                                      "SET table_id = " << quote << table_id << ", " <<
                                      "engine_type = " << engine_type << ", " <<
                                      "file_id = " << quote << file_id << ", " <<
                                      "file_type = " << file_type << ", " <<
                                      "file_size = " << file_size << ", " <<
                                      "row_count = " << row_count << ", " <<
                                      "updated_time = " << updated_time << ", " <<
                                      "created_on = " << created_on << ", " <<
                                      "date = " << date << " " <<
                                      "WHERE id = " << id << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::UpdateTableFiles: " << updateTableFilesQuery.str();

                if (!updateTableFilesQuery.exec()) {
                    ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FILES";
                    return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FILES",
                                                      updateTableFilesQuery.error());
                }
            }
        } //Scoped Connection

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN UPDATING TABLE FILES" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN UPDATING TABLE FILES", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN UPDATING TABLE FILES" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN UPDATING TABLE FILES", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::CleanUpFilesWithTTL(uint16_t seconds) {
    auto now = utils::GetMicroSecTimeStamp();
    std::set<std::string> table_ids;

    //remove to_delete files
    try {
        server::MetricCollector metric;

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query cleanUpFilesWithTTLQuery = connectionPtr->query();
            cleanUpFilesWithTTLQuery << "SELECT id, table_id, file_id, date " <<
                                     "FROM TableFiles " <<
                                     "WHERE file_type = " << std::to_string(TableFileSchema::TO_DELETE) << " AND " <<
                                     "updated_time < " << std::to_string(now - seconds * US_PS) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::CleanUpFilesWithTTL: " << cleanUpFilesWithTTLQuery.str();

            StoreQueryResult res = cleanUpFilesWithTTLQuery.store();

            TableFileSchema table_file;
            std::vector<std::string> idsToDelete;

            for (auto &resRow : res) {

                table_file.id_ = resRow["id"]; //implicit conversion

                std::string table_id;
                resRow["table_id"].to_string(table_id);
                table_file.table_id_ = table_id;

                std::string file_id;
                resRow["file_id"].to_string(file_id);
                table_file.file_id_ = file_id;

                table_file.date_ = resRow["date"];

                utils::DeleteTableFilePath(options_, table_file);

                ENGINE_LOG_DEBUG << "Removing file id:" << table_file.id_ << " location:" << table_file.location_;

                idsToDelete.emplace_back(std::to_string(table_file.id_));

                table_ids.insert(table_file.table_id_);
            }

            if (!idsToDelete.empty()) {

                std::stringstream idsToDeleteSS;
                for (auto &id : idsToDelete) {
                    idsToDeleteSS << "id = " << id << " OR ";
                }

                std::string idsToDeleteStr = idsToDeleteSS.str();
                idsToDeleteStr = idsToDeleteStr.substr(0, idsToDeleteStr.size() - 4); //remove the last " OR "
                cleanUpFilesWithTTLQuery << "DELETE FROM TableFiles WHERE " <<
                                         idsToDeleteStr << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::CleanUpFilesWithTTL: " << cleanUpFilesWithTTLQuery.str();

                if (!cleanUpFilesWithTTLQuery.exec()) {
                    ENGINE_LOG_ERROR << "QUERY ERROR WHEN CLEANING UP FILES WITH TTL";
                    return Status::DBTransactionError("CleanUpFilesWithTTL Error",
                                                      cleanUpFilesWithTTLQuery.error());
                }
            }
        } //Scoped Connection

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN CLEANING UP FILES WITH TTL" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN CLEANING UP FILES WITH TTL", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN CLEANING UP FILES WITH TTL" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN CLEANING UP FILES WITH TTL", er.what());
    }

    //remove to_delete tables
    try {
        server::MetricCollector metric;

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            Query cleanUpFilesWithTTLQuery = connectionPtr->query();
            cleanUpFilesWithTTLQuery << "SELECT id, table_id " <<
                                     "FROM Tables " <<
                                     "WHERE state = " << std::to_string(TableSchema::TO_DELETE) << ";";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::CleanUpFilesWithTTL: " << cleanUpFilesWithTTLQuery.str();

            StoreQueryResult res = cleanUpFilesWithTTLQuery.store();

            if (!res.empty()) {

                std::stringstream idsToDeleteSS;
                for (auto &resRow : res) {
                    size_t id = resRow["id"];
                    std::string table_id;
                    resRow["table_id"].to_string(table_id);

                    utils::DeleteTablePath(options_, table_id, false);//only delete empty folder

                    idsToDeleteSS << "id = " << std::to_string(id) << " OR ";
                }
                std::string idsToDeleteStr = idsToDeleteSS.str();
                idsToDeleteStr = idsToDeleteStr.substr(0, idsToDeleteStr.size() - 4); //remove the last " OR "
                cleanUpFilesWithTTLQuery << "DELETE FROM Tables WHERE " <<
                                         idsToDeleteStr << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::CleanUpFilesWithTTL: " << cleanUpFilesWithTTLQuery.str();

                if (!cleanUpFilesWithTTLQuery.exec()) {
                    ENGINE_LOG_ERROR << "QUERY ERROR WHEN CLEANING UP FILES WITH TTL";
                    return Status::DBTransactionError("QUERY ERROR WHEN CLEANING UP FILES WITH TTL",
                                                      cleanUpFilesWithTTLQuery.error());
                }
            }
        } //Scoped Connection

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN CLEANING UP FILES WITH TTL" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN CLEANING UP FILES WITH TTL", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN CLEANING UP FILES WITH TTL" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN CLEANING UP FILES WITH TTL", er.what());
    }

    //remove deleted table folder
    //don't remove table folder until all its files has been deleted
    try {
        server::MetricCollector metric;

        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }

            for(auto& table_id : table_ids) {
                Query cleanUpFilesWithTTLQuery = connectionPtr->query();
                cleanUpFilesWithTTLQuery << "SELECT file_id " <<
                                         "FROM TableFiles " <<
                                         "WHERE table_id = " << quote << table_id << ";";

                ENGINE_LOG_DEBUG << "MySQLMetaImpl::CleanUpFilesWithTTL: " << cleanUpFilesWithTTLQuery.str();

                StoreQueryResult res = cleanUpFilesWithTTLQuery.store();

                if (res.empty()) {
                    utils::DeleteTablePath(options_, table_id);
                }
            }
        }
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN CLEANING UP FILES WITH TTL" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN CLEANING UP FILES WITH TTL", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN CLEANING UP TABLES WITH TTL" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN CLEANING UP TABLES WITH TTL", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::CleanUp() {
    try {
        ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

        if (connectionPtr == nullptr) {
            return Status::Error("Failed to connect to database server");
        }

        Query cleanUpQuery = connectionPtr->query();
        cleanUpQuery << "SELECT table_name " <<
                     "FROM information_schema.tables " <<
                     "WHERE table_schema = " << quote << mysql_connection_pool_->getDB() << " " <<
                     "AND table_name = " << quote << "TableFiles" << ";";

        ENGINE_LOG_DEBUG << "MySQLMetaImpl::CleanUp: " << cleanUpQuery.str();

        StoreQueryResult res = cleanUpQuery.store();

        if (!res.empty()) {
            ENGINE_LOG_DEBUG << "Remove table file type as NEW";
            cleanUpQuery << "DELETE FROM TableFiles WHERE file_type IN ("
                    << std::to_string(TableFileSchema::NEW) << ","
                    << std::to_string(TableFileSchema::NEW_MERGE) << ","
                    << std::to_string(TableFileSchema::NEW_INDEX) << ");";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::CleanUp: " << cleanUpQuery.str();

            if (!cleanUpQuery.exec()) {
                ENGINE_LOG_ERROR << "QUERY ERROR WHEN CLEANING UP FILES";
                return Status::DBTransactionError("Clean up Error", cleanUpQuery.error());
            }
        }

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN CLEANING UP FILES" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN CLEANING UP FILES", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN CLEANING UP FILES" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN CLEANING UP FILES", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::Count(const std::string &table_id, uint64_t &result) {
    try {
        server::MetricCollector metric;

        TableSchema table_schema;
        table_schema.table_id_ = table_id;
        auto status = DescribeTable(table_schema);

        if (!status.ok()) {
            return status;
        }

        StoreQueryResult res;
        {
            ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

            if (connectionPtr == nullptr) {
                return Status::Error("Failed to connect to database server");
            }


            Query countQuery = connectionPtr->query();
            countQuery << "SELECT size " <<
                       "FROM TableFiles " <<
                       "WHERE table_id = " << quote << table_id << " AND " <<
                       "(file_type = " << std::to_string(TableFileSchema::RAW) << " OR " <<
                       "file_type = " << std::to_string(TableFileSchema::TO_INDEX) << " OR " <<
                       "file_type = " << std::to_string(TableFileSchema::INDEX) << ");";

            ENGINE_LOG_DEBUG << "MySQLMetaImpl::Count: " << countQuery.str();

            res = countQuery.store();
        } //Scoped Connection

        result = 0;
        for (auto &resRow : res) {
            size_t size = resRow["size"];
            result += size;
        }

        if (table_schema.dimension_ <= 0) {
            std::stringstream errorMsg;
            errorMsg << "MySQLMetaImpl::Count: " << "table dimension = " << std::to_string(table_schema.dimension_)
                     << ", table_id = " << table_id;
            ENGINE_LOG_ERROR << errorMsg.str();
            return Status::Error(errorMsg.str());
        }
        result /= table_schema.dimension_;
        result /= sizeof(float);

    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN RETRIEVING COUNT" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN RETRIEVING COUNT", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN RETRIEVING COUNT" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN RETRIEVING COUNT", er.what());
    }

    return Status::OK();
}

Status MySQLMetaImpl::DropAll() {
    if (boost::filesystem::is_directory(options_.path)) {
        boost::filesystem::remove_all(options_.path);
    }
    try {
        ScopedConnection connectionPtr(*mysql_connection_pool_, safe_grab);

        if (connectionPtr == nullptr) {
            return Status::Error("Failed to connect to database server");
        }

        Query dropTableQuery = connectionPtr->query();
        dropTableQuery << "DROP TABLE IF EXISTS Tables, TableFiles;";

        ENGINE_LOG_DEBUG << "MySQLMetaImpl::DropAll: " << dropTableQuery.str();

        if (dropTableQuery.exec()) {
            return Status::OK();
        } else {
            ENGINE_LOG_ERROR << "QUERY ERROR WHEN DROPPING TABLE";
            return Status::DBTransactionError("DROP TABLE ERROR", dropTableQuery.error());
        }
    } catch (const BadQuery &er) {
        // Handle any query errors
        ENGINE_LOG_ERROR << "QUERY ERROR WHEN DROPPING TABLE" << ": " << er.what();
        return Status::DBTransactionError("QUERY ERROR WHEN DROPPING TABLE", er.what());
    } catch (const Exception &er) {
        // Catch-all for any other MySQL++ exceptions
        ENGINE_LOG_ERROR << "GENERAL ERROR WHEN DROPPING TABLE" << ": " << er.what();
        return Status::DBTransactionError("GENERAL ERROR WHEN DROPPING TABLE", er.what());
    }

    return Status::OK();
}

MySQLMetaImpl::~MySQLMetaImpl() {
    if (mode_ != Options::MODE::READ_ONLY) {
        CleanUp();
    }
}

} // namespace meta
} // namespace engine
} // namespace milvus
} // namespace zilliz