并发访问sqlite数据库出现databse is locked的错误的一个解决办法

太过爱你忘了你带给我的痛 2022-08-22 12:23 147阅读 0赞

作者：朱金灿

来源：[http://blog.csdn.net/clever101][http_blog.csdn.net_clever101]

在并发访问sqlite数据库会出现这样一个错误：databseis locked，这是sqlite数据库对并发支持不太好的缘故造成的。采用网上的一种的思路是通过互斥信号量来达到并发访问的目的。下面是一个跨平台的互斥信号量类：

//ProcessMutex.h文件： 
    #ifndef __PROCESS_MUTEX_H__
    #define __PROCESS_MUTEX_H__
     
    #if defined _WIN32 || defined _WIN64
    
         #include <Windows.h>
    
    #endif
     
    #ifdef linux
    #include <unistd.h>
    #include <semaphore.h>
    #include <stdio.h>
    #include <fcntl.h>
    #include <signal.h>
    #include <string.h>
    #include <memory.h>
    #endif
     
    class CProcessMutex
    {
    public:
        /* 默认创建匿名的互斥 */
        CProcessMutex(const char* name = NULL);
        ~CProcessMutex();
     
        bool Lock();
        bool UnLock();
    private:
    
    #if defined _WIN32 || defined _WIN64
    
        void* m_pMutex;
    
    #endif
    
    #ifdef linux
        set_t* m_pSem;
    #ednif
        char m_cMutexName[30];
    };
    #endif
    
     //ProcessMutex.cpp文件：
    #include "ProcessMutex.h"
     
    #if defined _WIN32 || defined _WIN64
     
    CProcessMutex::CProcessMutex(const char* name)
    {
        memset(m_cMutexName, 0 ,sizeof(m_cMutexName));
        int min = strlen(name)>(sizeof(m_cMutexName)-1)?(sizeof(m_cMutexName)-1):strlen(name);
        strncpy(m_cMutexName, name, min);
        m_pMutex = CreateMutex(NULL, false, m_cMutexName);
    }
     
    CProcessMutex::~CProcessMutex()
    {
        CloseHandle(m_pMutex);
    }
     
    bool CProcessMutex::Lock()
    {
        //互斥锁创建失败
        if (NULL == m_pMutex)
        {
            return false;
        }
         
        DWORD nRet = WaitForSingleObject(m_pMutex, INFINITE);
        if (nRet != WAIT_OBJECT_0)
        {
            return false;
        }
     
        return true;
    }
     
    bool CProcessMutex::UnLock()
    {
        return ReleaseMutex(m_pMutex);
    }
     
    #endif
     
    #ifdef linux
     
    CProcessMutex::CProcessMutex(const char* name)
    {
        memset(m_cMutexName, 0 ,sizeof(m_cMutexName));
        int min = strlen(name)>(sizeof(m_cMutexName)-1)?(sizeof(m_cMutexName)-1):strlen(name);
        strncpy(m_cMutexName, name, min);
        m_pSem = sem_open(name, O_CREAT, 0644, 1);
    }
     
    CProcessMutex::~CProcessMutex()
    {
        int ret = sem_close(m_pSem);
        if (0 != ret)
        {
            printf("sem_close error %d\n", ret);
        }
        sem_unlink(m_cMutexName);
    }
     
    bool CProcessMutex::Lock()
    {
        int ret = sem_wait(m_pSem);
        if (ret != 0)
        {
            return false;
        }
        return true;
    }
     
    bool CProcessMutex::UnLock()
    {
        int ret = sem_post(m_pSem);
        if (ret != 0)
        {
            return false;
        }
        return true;
    }
     
    #endif

使用示例代码如下：

CProcessMutex pMutex("MutexName");
    
    pMutex.Lock();
    
    sqlite3_exec( myconn, sql, 0, 0, &m_sqlerr_msg); // 执行sqlite的相关操作
    
    pMutex.UnLock();

参考文献：

1. [多进程之间的互斥信号量的实现（Linux和windows跨平台）][Linux_windows]

2.[sqlite遇到database is locked问题的完美解决][sqlite_database is locked]

[http_blog.csdn.net_clever101]: http://blog.csdn.net/clever101
[Linux_windows]: http://my.oschina.net/u/929521/blog/645678
[sqlite_database is locked]: http://www.cnblogs.com/Bonker/p/3445240.html