利用MysqlUDF编写Memcached扩展函数

一、安装Memcached和客户端库LibMemcached

Memcached下载地址：http://memcached.org
LibMemcached下载地址：http://libmemcached.org
（官网有安装方法，略）

二、用C/C++封装方法（如 set方法 和 get方法）

#include <stdio.h>#include <string.h>#include <stdlib.h>#include <string>#include "mysql.h"#include <libmemcached/memcached.h>using namespace std;const char *memServer="127.0.0.1";int memcPort=11211;extern "C" long long memc_set(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error)  {        memcached_server_st *servers = NULL;      memcached_st *memc;      memcached_return rc;     char *keyField = (char *)args->args[0]; //cache key add by shenyi     char *valueField =(char *)args->args[1]; //cache value  add by shenyi     int timeField=atoi(args->args[2]); //cache time add by shenyi     memcached_server_st *memcached_servers_parse (char *server_strings);     memc= memcached_create(NULL);     servers= memcached_server_list_append(servers, memServer, memcPort, &rc);     rc= memcached_server_push(memc, servers);     if (rc != MEMCACHED_SUCCESS)    {        strcpy(error,"Couldn't add server");          memcached_free(memc);        return 0;    }     //this is libmemcached set function and params  add by shenyi     rc= memcached_set(memc, keyField, strlen(keyField), valueField, strlen(valueField), (time_t)timeField, (uint32_t)0);     if (rc != MEMCACHED_SUCCESS)     {         strcpy(error,"Couldn't set value");           memcached_server_list_free(servers);         memcached_free(memc);        return 0;     }      memcached_server_list_free(servers);      memcached_free(memc);     return 1;}  extern "C" my_bool memc_set_init(UDF_INIT *initid, UDF_ARGS *args, char *message)  {      if(args->arg_count!=3){        strcpy(            message        ,   "Memc_set expected exactly three arguments,like key value time"        );      // error msg add by shenyi        return 1;    }    return 0;}  extern "C" char *memc_get(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error)  {        memcached_server_st *servers = NULL;      memcached_st *memc;      memcached_return rc;      size_t return_key_length;      size_t return_value_length;      char *return_value;       uint32_t flags = 0;     const  char *keyField = (const char *)args->args[0]; //cache key add by shenyi     memcached_server_st *memcached_servers_parse (char *server_strings);     memc= memcached_create(NULL);     servers= memcached_server_list_append(servers, memServer, memcPort, &rc);     rc= memcached_server_push(memc, servers);     //this is libmemcached get function and params  add by shenyi     return_value= memcached_get(memc, keyField,strlen(keyField), &return_value_length,&flags,&rc);    if (rc != MEMCACHED_SUCCESS || return_value==NULL )  //get null value or error add by shenyi     {          memcached_server_list_free(servers);         memcached_free(memc);         return NULL;     }      memcached_server_list_free(servers);      memcached_free(memc);     return return_value;}  extern "C" my_bool memc_get_init(UDF_INIT *initid, UDF_ARGS *args, char *message)  {      if(args->arg_count!=1){        strcpy(            message        ,   "Memc_get expected exactly ono arguments,like memc_get(xx)"        );      // error msg add by shenyi        return 1;    }    return 0;}  

三、编译

g++ -I /usr/include/mysql/ -L /usr/local/lib/ -l memcached -shared -fPIC -o mysql-memc.so mysql-memc.cpp --std=c++0x

四、部署插件

cp mysql-memc.so /usr/lib/mysql/plugin/

五、在 Mysql 中创建函数

CREATE FUNCTION memc_set RETURNS INTEGER SONAME 'mysql-memc.so';CREATE FUNCTION memc_get RETURNS STRING SONAME 'mysql-memc.so';

六、Mysql 操作 Memcached

select memc_set('name','jack','60');select memc_get('name');

#可能遇到的问题

和用UDF编写Redis扩展函数的问题一样，解决方法：
http://blog.csdn.net/txl13109187932/article/details/78885954