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MySQL因為它自己的玲珑和操作的高效, 在數據庫運用中愈來愈多的被采取.我在開辟一個P2P運用的時刻已經應用MySQL來保留P2P節點,因為P2P的運用中,結點數動辄上萬個,並且節點變更頻仍,是以必定要堅持查詢和拔出的高效.以下是我在應用進程中做的進步效力的三個有用的測驗考試.
l 應用statement停止綁定查詢
應用statement可以提早構建查詢語法樹,在查詢時不再須要構建語法樹就直接查詢.是以可以很好的進步查詢的效力. 這個辦法合適於查詢前提固定但查詢異常頻仍的場所.
應用辦法是:
綁定, 創立一個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,每一個問號都必需指定一個變量.
查詢, 輸出每一個指定的變量, 傳入MYSQL_STMT變量用可用的銜接句柄履行.
代碼以下:
//1.綁定
bool CDBManager::BindInsertStmt(MYSQL * connecthandle)
{
//作拔出操作的綁定
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構造數組, m_sInsertParam是這個statement聯系關系的構造變量
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)
{
//填充構造變量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;
//履行statement,機能瓶頸處
if(mysql_stmt_execute(m_stInsertStmt))
return false;
return true;
}
l 隨機的獲得記載
在某些數據庫的運用中, 我們其實不是要獲得一切的知足前提的記載,而只是要隨機遴選出知足前提的記載. 這類情形罕見於數據營業的統計剖析,從年夜容量數據庫中獲得小量的數據的場所.
有兩種辦法可以做到
1. 慣例辦法,起首查詢出一切知足前提的記載,然後隨機的遴選出部門記載.這類辦法在知足前提的記載數許多時後果不睬想.
2. 應用limit語法,先獲得知足前提的記載條數, 然後在sql查詢語句中參加limit來限制只查詢知足請求的一段記載. 這類辦法固然要查詢兩次,然則在數據量年夜時反而比擬高效.
示例代碼以下:
//1.慣例的辦法
//機能瓶頸,10萬筆記錄時,履行查詢140ms, 獲得成果集500ms,其他可疏忽
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;
//獲得成果集
m_pResultSet = mysql_store_result(connecthandle);
if(!m_pResultSet) //獲得成果集失足
return 0;
int iAllNumRows = (int)(mysql_num_rows(m_pResultSet)); ///<一切的搜刮成果數
//盤算待前往的成果數
int iReturnNumRows = (iAllNumRows <= RETURN_QUERY_HOST_NUM)? iAllNumRows:RETURN_QUERY_HOST_NUM;
if(iReturnNumRows <= RETURN_QUERY_HOST_NUM)
{
//獲得逐筆記錄
for(int i = 0; i<iReturnNumRows; i++)
{
//獲得逐一字段
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
{
//隨機的遴選指定筆記錄前往
int iRemainder = iAllNumRows%iReturnNumRows; ///<余數
int iQuotient = iAllNumRows/iReturnNumRows; ///<商
int iStartIndex = rand()%(iRemainder + 1); ///<開端下標
//獲得逐筆記錄
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]);
}
}
//釋放成果集內容
mysql_free_result(m_pResultSet);
return iReturnNumRows;
}
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