MySQL的UDF(User Defined Function)类似于一种API, 用户根据一定的规范用C/C++(或采用C调用规范的语言)编写一组函数(UDF)，然后编译成动态链接库，通过DROP FUNCTION语句来加载和卸载UDF。UDF被加载后可以像调用MySQL的内置函数一样来调用它，并且服务器在启动时会自动加载原来存在的UDF。

复制代码 代码如下:
#ifdef STANDARD
#include
#include
#include
#ifdef __WIN__
typedef unsigned __int64 ulonglong;   
typedef __int64 longlong;
#else
typedef unsigned long long ulonglong;
typedef long long longlong;
#endif
#else
#include
#include
#if defined(MYSQL_SERVER)
#include        
#else

#include
#endif
#endif
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#ifdef HAVE_DLOPEN

my_bool http_post_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
void http_post_deinit(UDF_INIT *initid);
longlong http_post(UDF_INIT *initid, UDF_ARGS *args, char *is_null,char *error);

my_bool http_post_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
if (args->arg_count {
    strcpy(message,"Wrong arguments to http_post; ");
    return 1;
}

if(args->arg_count == 4 && args->args[3]!=NULL)
{
      int flexibleLength = strlen(args->args[3]);
      if(flexibleLength > 160000)
      {
          int allocLength = 200 + flexibleLength;
          if (!(initid->ptr=(char*) malloc(allocLength) ) )
          {
                strcpy(message,"Couldn't allocate memory in http_post_init");
                return 1;
          }
        return 0;
      }
      else
      {
          initid->ptr=NULL;
    }

}
   return 0;

}

void http_post_deinit(UDF_INIT *initid)
{
     if (initid!=NULL && initid->ptr!=NULL)
          {
              free(initid->ptr);
              initid->ptr = NULL;
          }

}

longlong http_post(    UDF_INIT *initid, UDF_ARGS *args,
                char *is_null __attribute__((unused)),
                char *error __attribute__((unused)))
{
    int sockfd=0;
    int numbytes=0;
    int flags=0;
    int cycletimes=0;
    char* sendBuffer=NULL;

    fd_set wset;
    struct timeval tval;
    tval.tv_sec = 0;
    tval.tv_usec = 300000;

    if(initid->ptr == NULL)
    {
        char sendArray[160000] = "