提高MySQL查询效率的三个技巧(1)(3)

时间:2011-04-12 23:18来源:未知作者:admin 点击: 次

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设计代码如下： //定义句柄队列 typedef std::list CONNECTION_HANDLE_LIST; typedef std::list ::iterator CONNECTION_HANDLE_LIST_IT; //连接数据库的参数结构 class CDBParameter { publi

设计代码如下：

//定义句柄队列 
typedef std::list CONNECTION_HANDLE_LIST;
typedef std::list::iterator CONNECTION_HANDLE_LIST_IT;

//连接数据库的参数结构
class CDBParameter             
{
public:
char *host;                                 ///<主机名
char *user;                                 ///<用户名
char *password;                         ///<密码
char *database;                           ///<数据库名
unsigned int port;                 ///<端口，一般为0
const char *unix_socket;      ///<套接字，一般为NULL
unsigned int client_flag; ///<一般为0
};

//创建两个队列
CONNECTION_HANDLE_LIST m_lsBusyList;                ///<正在使用的连接句柄
CONNECTION_HANDLE_LIST m_lsIdleList;                  ///<未使用的连接句柄

//所有的连接句柄先连上数据库,加入到空闲队列中,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
{
//连接
for(int index = 0; index < CONNECTION_NUM; index++)
{
MYSQL * pConnectHandle = mysql_init((MYSQL*) 0);     
//初始化连接句柄
if(!mysql_real_connect(pConnectHandle, 
lpDBParam->host, lpDBParam->user, lpDBParam->password,
lpDBParam->database,lpDBParam->port,lpDBParam->unix_socket,
lpDBParam->client_fla))
return false;
//加入到空闲队列中
m_lsIdleList.push_back(pConnectHandle);
}
}
catch(...)
{
return false;
}
return true;
}

//提取一个空闲句柄供使用
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 //特殊情况,闲队列中为空,返回为空
{
pConnectHandle = 0;
}
m_ListMutex.release();

return pConnectHandle;
}

//从使用队列中释放一个使用完毕的句柄,插入到空闲队列
void CDBManager::SetIdleConnectHandle(MYSQL * connecthandle)
{
m_ListMutex.acquire();
m_lsBusyList.remove(connecthandle);
m_lsIdleList.push_back(connecthandle);
m_ListMutex.release();
}
//使用示例,首先获取空闲句柄,利用这个句柄做真正的操作,然后再插回到空闲队列
bool CDBManager::DeleteHostCacheBySessionID(char * sessionid)
{
MYSQL * pConnectHandle = GetIdleConnectHandle();
if(!pConnectHandle)
return 0;
bool bRet = DeleteHostCacheBySessionID(pConnectHandle, sessionid);
SetIdleConnectHandle(pConnectHandle);
return bRet;
}
//传入空闲的句柄,做真正的删除操作
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) //删除
return false;
return true;
}