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mysql 提高查詢速度實例

MySQL由於它本身的小巧和操作的高效, 在數據庫應用中越來越多的被采用.我在開發一個P2P應用的時候曾經使用MySQL來保存P2P節點,由於P2P的應用中,結點數動辄上萬個,而且節點變化頻繁,因此一定要保持查詢和插入的高效.以下是我在使用過程中做的提高效率的三個有效的嘗試. 1. 使用statement進行綁定查詢 2. 隨機的獲取記錄 3. 使用連接池管理連接.

MySQL由於它本身的小巧和操作的高效, 在數據庫應用中越來越多的被采用.我在開發一個P2P應用的時候曾經使用MySQL來保存P2P節點,由於P2P的應用中,結點數動辄上萬個,而且節點變化頻繁,因此一定要保持查詢和插入的高效.以下是我在使用過程中做的提高效率的三個有效的嘗試.
l        使用statement進行綁定查詢

使用statement可以提前構建查詢語法樹,在查詢時不再需要構建語法樹就直接查詢.因此可以很好的提高查詢的效率. 這個方法適合於查詢條件固定但查詢非常頻繁的場合. 使用方法是:
  1. 綁定, 創建一個MYSQL_STMT變量,與對應的查詢字符串綁定,字符串中的問號代表要傳入的變量,每個問號都必須指定一個變量.
  2. 查詢, 輸入每個指定的變量, 傳入MYSQL_STMT變量用可用的連接句柄執行.
代碼如下:   //1.綁定 bool CDBManager::BindInsertStmt(MYSQL * connecthandle) {        //作插入操作的綁定        MYSQL_BIND insertbind[FEILD_NUM];        if(m_stInsertParam == NULL)               m_stInsertParam = new CHostCacheTable;        m_stInsertStmt = mysql_stmt_init(connecthandle);        //構建綁定字符串        char insertSQL[SQL_LENGTH];        strcpy(insertSQL, "insert into HostCache(SessionID, ChannelID, ISPType, "               "ExternalIP, ExternalPort, InternalIP, InternalPort) "               "values(?, ?, ?, ?, ?, ?, ?)");        mysql_stmt_prepare(m_stInsertStmt, insertSQL, strlen(insertSQL));        int param_count= mysql_stmt_param_count(m_stInsertStmt);        if(param_count != FEILD_NUM)               return false;        //填充bind結構數組, m_sInsertParam是這個statement關聯的結構變量        memset(insertbind, 0, sizeof(insertbind));        insertbind[0].buffer_type = MYSQL_TYPE_STRING;        insertbind[0].buffer_length = ID_LENGTH /* -1 */;        insertbind[0].buffer = (char *)m_stInsertParam->sessionid;        insertbind[0].is_null = 0;        insertbind[0].length = 0;          insertbind[1].buffer_type = MYSQL_TYPE_STRING;        insertbind[1].buffer_length = ID_LENGTH /* -1 */;        insertbind[1].buffer = (char *)m_stInsertParam->channelid;        insertbind[1].is_null = 0;        insertbind[1].length = 0;          insertbind[2].buffer_type = MYSQL_TYPE_TINY;        insertbind[2].buffer = (char *)&m_stInsertParam->ISPtype;        insertbind[2].is_null = 0;        insertbind[2].length = 0;          insertbind[3].buffer_type = MYSQL_TYPE_LONG;        insertbind[3].buffer = (char *)&m_stInsertParam->externalIP;        insertbind[3].is_null = 0;        insertbind[3].length = 0;               insertbind[4].buffer_type = MYSQL_TYPE_SHORT;        insertbind[4].buffer = (char *)&m_stInsertParam->externalPort;        insertbind[4].is_null = 0;        insertbind[4].length = 0;          insertbind[5].buffer_type = MYSQL_TYPE_LONG;        insertbind[5].buffer = (char *)&m_stInsertParam->internalIP;        insertbind[5].is_null = 0;        insertbind[5].length = 0;          insertbind[6].buffer_type = MYSQL_TYPE_SHORT;        insertbind[6].buffer = (char *)&m_stInsertParam->internalPort;        insertbind[6].is_null = 0;        insertbind[6].is_null = 0;        //綁定        if (mysql_stmt_bind_param(m_stInsertStmt, insertbind))               return false;        return true; }   //2.查詢 bool CDBManager::InsertHostCache2(MYSQL * connecthandle, char * sessionid, char * channelid, int ISPtype,               unsigned int eIP, unsigned short eport, unsigned int iIP, unsigned short iport) {        //填充結構變量m_sInsertParam        strcpy(m_stInsertParam->sessionid, sessionid);        strcpy(m_stInsertParam->channelid, channelid);        m_stInsertParam->ISPtype = ISPtype;        m_stInsertParam->externalIP = eIP;        m_stInsertParam->externalPort = eport;        m_stInsertParam->internalIP = iIP;        m_stInsertParam->internalPort = iport;        //執行statement,性能瓶頸處        if(mysql_stmt_execute(m_stInsertStmt))               return false;        return true; }   l         隨機的獲取記錄 在某些數據庫的應用中, 我們並不是要獲取所有的滿足條件的記錄,而只是要隨機挑選出滿足條件的記錄. 這種情況常見於數據業務的統計分析,從大容量數據庫中獲取小量的數據的場合.       有兩種方法可以做到 1.       常規方法,首先查詢出所有滿足條件的記錄,然後隨機的挑選出部分記錄.這種方法在滿足條件的記錄數很多時效果不理想. 2.       使用limit語法,先獲取滿足條件的記錄條數, 然後在sql查詢語句中加入limit來限制只查詢滿足要求的一段記錄. 這種方法雖然要查詢兩次,但是在數據量大時反而比較高效. 示例代碼如下:   //1.常規的方法 //性能瓶頸,10萬條記錄時,執行查詢140ms, 獲取結果集500ms,其余可忽略 int CDBManager::QueryHostCache(MYSQL* connecthandle, char * channelid, int ISPtype, CDBManager::CHostCacheTable * &hostcache) {            char selectSQL[SQL_LENGTH];        memset(selectSQL, 0, sizeof(selectSQL));        sprintf(selectSQL,"select * from HostCache where ChannelID = ‘%s‘ and ISPtype = %d", channelid, ISPtype);        if(mysql_real_query(connecthandle, selectSQL, strlen(selectSQL)) != 0)   //檢索               return 0;        //獲取結果集        m_pResultSet = mysql_store_result(connecthandle);        if(!m_pResultSet)   //獲取結果集出錯               return 0;        int iAllNumRows = (int)(mysql_num_rows(m_pResultSet));      ///<所有的搜索結果數        //計算待返回的結果數        int iReturnNumRows = (iAllNumRows <= RETURN_QUERY_HOST_NUM)? iAllNumRows:RETURN_QUERY_HOST_NUM;        if(iReturnNumRows <= RETURN_QUERY_HOST_NUM)        {               //獲取逐條記錄               for(int i = 0; i<iReturnNumRows; i++)               {                      //獲取逐個字段                      m_Row = mysql_fetch_row(m_pResultSet);                      if(m_Row[0] != NULL)                             strcpy(hostcache[i].sessionid, m_Row[0]);                      if(m_Row[1] != NULL)                             strcpy(hostcache[i].channelid, m_Row[1]);                      if(m_Row[2] != NULL)                             hostcache[i].ISPtype      = atoi(m_Row[2]);                      if(m_Row[3] != NULL)                             hostcache[i].externalIP   = atoi(m_Row[3]);                      if(m_Row[4] != NULL)                             hostcache[i].externalPort = atoi(m_Row[4]);                      if(m_Row[5] != NULL)                             hostcache[i].internalIP   = atoi(m_Row[5]);                      if(m_Row[6] != NULL)                             hostcache[i].internalPort = atoi(m_Row[6]);                            }        }        else        {               //隨機的挑選指定條記錄返回               int iRemainder = iAllNumRows%iReturnNumRows;    ///<余數               int iQuotient = iAllNumRows/iReturnNumRows;      ///<商               int iStartIndex = rand()%(iRemainder + 1);         ///<開始下標                //獲取逐條記錄         for(int iSelectedIndex = 0; iSelectedIndex < iReturnNumRows; iSelectedIndex++)         {                             mysql_data_seek(m_pResultSet, iStartIndex + iQuotient * iSelectedIndex);                             m_Row = mysql_fetch_row(m_pResultSet);                   if(m_Row[0] != NULL)                        strcpy(hostcache[iSelectedIndex].sessionid, m_Row[0]);                    if(m_Row[1] != NULL)                                    strcpy(hostcache[iSelectedIndex].channelid, m_Row[1]);                    if(m_Row[2] != NULL)                        hostcache[iSelectedIndex].ISPtype      = atoi(m_Row[2]);                    if(m_Row[3] != NULL)                        hostcache[iSelectedIndex].externalIP   = atoi(m_Row[3]);                     if(m_Row[4] != NULL)                        hostcache[iSelectedIndex].externalPort = atoi(m_Row[4]);                    if(m_Row[5] != NULL)                        hostcache[iSelectedIndex].internalIP   = atoi(m_Row[5]);                    if(m_Row[6] != NULL)                        hostcache[iSelectedIndex].internalPort = atoi(m_Row[6]);         }       }        //釋放結果集內容        mysql_free_result(m_pResultSet);        return iReturnNumRows; }   //2.使用limit版 int CDBManager::QueryHostCache(MYSQL * connecthandle, char * channelid, unsigned int myexternalip, int ISPtype, CHostCacheTable * hostcache) {        //首先獲取滿足結果的記錄條數,再使用limit隨機選擇指定條記錄返回        MYSQL_ROW row;        MYSQL_RES * pResultSet;        char selectSQL[SQL_LENGTH];        memset(selectSQL, 0, sizeof(selectSQL));          sprintf(selectSQL,"select count(*) from HostCache where ChannelID = ‘%s‘ and ISPtype = %d", channelid, ISPtype);        if(mysql_real_query(connecthandle, selectSQL, strlen(selectSQL)) != 0)   //檢索               return 0;        pResultSet = mysql_store_result(connecthandle);        if(!pResultSet)                     return 0;        row = mysql_fetch_row(pResultSet);        int iAllNumRows = atoi(row[0]);        mysql_free_result(pResultSet);        //計算待取記錄的上下范圍        int iLimitLower = (iAllNumRows <= RETURN_QUERY_HOST_NUM)?               0:(rand()%(iAllNumRows - RETURN_QUERY_HOST_NUM));        int iLimitUpper = (iAllNumRows <= RETURN_QUERY_HOST_NUM)?               iAllNumRows:(iLimitLower + RETURN_QUERY_HOST_NUM);        //計算待返回的結果數        int iReturnNumRows = (iAllNumRows <= RETURN_QUERY_HOST_NUM)?                iAllNumRows:RETURN_QUERY_HOST_NUM;               //使用limit作查詢        sprintf(selectSQL,"select SessionID, ExternalIP, ExternalPort, InternalIP, InternalPort "               "from HostCache where ChannelID = ‘%s‘ and ISPtype = %d limit %d, %d"               , channelid, ISPtype, iLimitLower, iLimitUpper);        if(mysql_real_query(connecthandle, selectSQL, strlen(selectSQL)) != 0)   //檢索               return 0;        pResultSet = mysql_store_result(connecthandle);        if(!pResultSet)               return 0;        //獲取逐條記錄        for(int i = 0; i<iReturnNumRows; i++)        {               //獲取逐個字段               row = mysql_fetch_row(pResultSet);               if(row[0] != NULL)                      strcpy(hostcache[i].sessionid, row[0]);               if(row[1] != NULL)                      hostcache[i].externalIP   = atoi(row[1]);               if(row[2] != NULL)                      hostcache[i].externalPort = atoi(row[2]);               if(row[3] != NULL)                      hostcache[i].internalIP   = atoi(row[3]);               if(row[4] != NULL)                      hostcache[i].internalPort = atoi(row[4]);                    }        //釋放結果集內容        mysql_free_result(pResultSet);        return iReturnNumRows; }   l         使用連接池管理連接. 在有大量節點訪問的數據庫設計中,經常要使用到連接池來管理所有的連接. 一般方法是:建立兩個連接句柄隊列,空閒的等待使用的隊列和正在使用的隊列. 當要查詢時先從空閒隊列中獲取一個句柄,插入到正在使用的隊列,再用這個句柄做數據庫操作,完畢後一定要從使用隊列中刪除,再插入到空閒隊列. 設計代碼如下:   //定義句柄隊列 typedef std::list<MYSQL *> CONNECTION_HANDLE_LIST; typedef std::list<MYSQL *>::iterator CONNECTION_HANDLE_LIST_IT;   //連接數據庫的參數結構 class CDBParameter             { public:        char *host;                                 ///<主機名        char *user;                                 ///<用戶名        char *password;                         ///<密碼        char *database;                           ///<數據庫名        unsigned int port;                 ///<端口,一般為0        const char *unix_socket;      ///<套接字,一般為NULL        unsigned int client_flag; ///<一般為0 };   //創建兩個隊列 CONNECTION_HANDLE_LIST m_lsBusyList;                ///<正在使用的連接句柄 CONNECTION_HANDLE_LIST m_lsIdleList;                  ///<未使用的連接句柄   //所有的連接句柄先連上數據庫,加入到空閒隊列中,等待使用. bool CDBManager::Connect(char * host /* = "localhost" */, char * user /* = "chenmin" */,                                             char * password /* = "chenmin" */, char * database /* = "HostCache" */) {        CDBParameter * lpDBParam = new CDBParameter();        lpDBParam->host = host;        lpDBParam->user = user;        lpDBParam->password = password;        lpDBParam->database = database;        lpDBParam->port = 0;        lpDBParam->unix_socket = NULL;        lpDBParam->client_flag = 0;        try        {               //連接               for(int index = 0; index < CONNECTION_NUM; index++)               {                      MYSQL * pConnectHandle = mysql_init((MYSQL*) 0);     //初始化連接句柄                      if(!mysql_real_connect(pConnectHandle, lpDBParam->host, lpDBParam->user, lpDBParam->password,        lpDBParam->database,lpDBParam->port,lpDBParam->unix_socket,lpDBParam->client_fla))                             return false; //加入到空閒隊列中                      m_lsIdleList.push_back(pConnectHandle);               }        }        catch(...)        {               return false;        }        return true; }   //提取一個空閒句柄供使用 MYSQL * CDBManager::GetIdleConnectHandle() {        MYSQL * pConnectHandle = NULL;        m_ListMutex.acquire();        if(m_lsIdleList.size())        {               pConnectHandle = m_lsIdleList.front();                     m_lsIdleList.pop_front();               m_lsBusyList.push_back(pConnectHandle);        }        else //特殊情況,閒隊列中為空,返回為空        {               pConnectHandle = 0;        }        m_ListMutex.release();          return pConnectHandle; }   //從使用隊列中釋放一個使用完畢的句柄,插入到空閒隊列 void CDBManager::SetIdleConnectHandle(MYSQL * connecthandle) {        m_ListMutex.acquire();        m_lsBusyList.remove(connecthandle);        m_lsIdleList.push_back(connecthandle);        m_ListMutex.release(); } //使用示例,首先獲取空閒句柄,利用這個句柄做真正的操作,然後再插回到空閒隊列 bool CDBManager::DeleteHostCacheBySessionID(char * sessionid) {        MYSQL * pConnectHandle = GetIdleConnectHandle();        if(!pConnectHandle)               return 0;        bool bRet = DeleteHostCacheBySessionID(pConnectHandle, sessionid);        SetIdleConnectHandle(pConnectHandle);        return bRet; } //傳入空閒的句柄,做真正的刪除操作 bool CDBManager::DeleteHostCacheBySessionID(MYSQL * connecthandle, char * sessionid) {        char deleteSQL[SQL_LENGTH];        memset(deleteSQL, 0, sizeof(deleteSQL));        sprintf(deleteSQL,"delete from HostCache where SessionID = ‘%s‘", sessionid);        if(mysql_query(connecthandle,deleteSQL) != 0) //刪除               return false;        return true;
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