在Mysql的官方文档中有说明如何给Mysql添加新的函数。

添加的函数可分为3种：

.自行编写函数的源码，将源码编译成动态库，然后使用Mysql的CREATE FUNCTION语句来将函数添加进Mysql。

.在源码等级上加入自行编写的函数，这样编译之后，新加入的函数就和Native函数一样，永久使用。

.通过SQL语句脚本来完成函数的功能。

就这3中方式，第三种明显不足以完成我们所需要的业务工作，因为SQL语句不存在连接缓存的功能。第二种方法看似美好，

但是对于需要更换缓存方法（从redis更换成memcached），重新编译数据库源码，这种不符合工程化商务化。

所以采用第一种方法自行编写函数代码，动态导入函数到mysql之中。
[root@server-mysql ~]# vi test_add.cpp

#include <mysql.h>

extern "C" long long testadd(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error)

{

        int a = *((long long *)args->args[]);

        int b = *((long long *)args->args[]);

        return a + b;

}

extern "C" my_bool testadd_init(UDF_INIT *initid, UDF_ARGS *args, char *message)

{

        return 0;

}
[root@server-mysql ~]# g++ -shared -fPIC -I /usr/local/mysql56/include -otest_add.so test_add.cpp

[root@server-mysql ~]# cp test_add.so /usr/local/mysql56/lib/plugin
my.cnf

plugin-load=test_add.so

mysql> use mysql;

Reading table information for completion of table and column names

You can turn off this feature to get a quicker startup with -A

Database changed

mysql> CREATE FUNCTION testadd RETURNS INTEGER SONAME 'test_add.so';

Query OK,  rows affected (0.16 sec)

mysql> select testadd(,);

+--------------+

| testadd(,) |

+--------------+

|             |

+--------------+

 row in set (0.00 sec)
mysql> select * from func;

+---------+-----+-------------+----------+

| name    | ret | dl          | type     |

+---------+-----+-------------+----------+

| testadd |    | test_add.so | function |

+---------+-----+-------------+----------+

 row in set (0.07 sec)
func表格记录了所有UDF函数的信息，表格中ret代表的是返回值类型，之所以这里记录的是2，是因为我们返回的是整型数据，可以在mysql的源码中sql目录下的mysql_com.h找到类型的枚举定义。

enum Item_result {STRING_RESULT=, REAL_RESULT, INT_RESULT, ROW_RESULT, DECIMAL_RESULT};

udf安全性:

#include <mysql.h>

#include <malloc.h>  

extern "C" long long testadd(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error)

{

    int a = *((long long *)args->args[]);

    int b = *((long long *)args->args[]);  

    int *p = (int *)malloc(sizeof(int));

    free(p);

    free(p);

    return a + b;

}  

extern "C" my_bool testadd_init(UDF_INIT *initid, UDF_ARGS *args, char *message)

{

    return ;

}  
mysql> select testadd(1,2);

ERROR 2013 (HY000): Lost connection to MySQL server during query
[root@server-mysql log]# *** glibc detected *** /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld: double free or corruption (fasttop): 0x00007ff00c05cf00 ***

======= Backtrace: =========

/lib64/libc.so.6[0x36bb075366]

/usr/local/mysql56/lib/plugin/test_add.so(testadd+0x64)[0x7ff02ab5a6e0]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_ZN17Item_func_udf_int7val_intEv+0x66)[0x5f4606]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_ZN4Item4sendEP8ProtocolP6String+0x1a1)[0x59bf41]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_ZN8Protocol19send_result_set_rowEP4ListI4ItemE+0x92)[0x66edf2]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_ZN11select_send9send_dataER4ListI4ItemE+0x6c)[0x6b7bbc]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_ZN4JOIN4execEv+0x608)[0x6d1488]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld[0x718039]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_Z12mysql_selectP3THDP10TABLE_LISTjR4ListI4ItemEPS4_P10SQL_I_ListI8st_orderESB_S7_yP13select_resultP18st_select_lex_unitP13st_select_lex+0xbc)[0x718afc]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_Z13handle_selectP3THDP13select_resultm+0x175)[0x718d05]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld[0x6f34d9]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_Z21mysql_execute_commandP3THD+0x3575)[0x6f7c95]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_Z11mysql_parseP3THDPcjP12Parser_state+0x338)[0x6fb7c8]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0xc60)[0x6fcba0]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_Z10do_commandP3THD+0xd7)[0x6fe997]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(_Z24do_handle_one_connectionP3THD+0x116)[0x6c5906]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(handle_one_connection+0x45)[0x6c59e5]

/usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld(pfs_spawn_thread+0x126)[0xae0596]

/lib64/libpthread.so.0[0x36bb807851]

/lib64/libc.so.6(clone+0x6d)[0x36bb0e767d]

======= Memory map: ========

00400000-00f9f000 r-xp 00000000 08:03 423182                             /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld

0119e000-0134c000 rw-p 00b9e000 08:03 423182                             /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/bin/mysqld

0134c000-0139d000 rw-p 00000000 00:00 0

01518000-0198e000 rw-p 00000000 00:00 0                                  [heap]

36ba800000-36ba820000 r-xp 00000000 08:03 824743                         /lib64/ld-2.12.so

36baa1f000-36baa20000 r--p 0001f000 08:03 824743                         /lib64/ld-2.12.so

36baa20000-36baa21000 rw-p 00020000 08:03 824743                         /lib64/ld-2.12.so

36baa21000-36baa22000 rw-p 00000000 00:00 0

36bac00000-36bac01000 r-xp 00000000 08:03 806064                         /lib64/libaio.so.1.0.1

36bac01000-36bae00000 ---p 00001000 08:03 806064                         /lib64/libaio.so.1.0.1

36bae00000-36bae01000 rw-p 00000000 08:03 806064                         /lib64/libaio.so.1.0.1

36bb000000-36bb189000 r-xp 00000000 08:03 824744                         /lib64/libc-2.12.so

36bb189000-36bb388000 ---p 00189000 08:03 824744                         /lib64/libc-2.12.so

36bb388000-36bb38c000 r--p 00188000 08:03 824744                         /lib64/libc-2.12.so

36bb38c000-36bb38d000 rw-p 0018c000 08:03 824744                         /lib64/libc-2.12.so

36bb38d000-36bb392000 rw-p 00000000 00:00 0

36bb400000-36bb402000 r-xp 00000000 08:03 824750                         /lib64/libdl-2.12.so

36bb402000-36bb602000 ---p 00002000 08:03 824750                         /lib64/libdl-2.12.so

36bb602000-36bb603000 r--p 00002000 08:03 824750                         /lib64/libdl-2.12.so

36bb603000-36bb604000 rw-p 00003000 08:03 824750                         /lib64/libdl-2.12.so

36bb800000-36bb817000 r-xp 00000000 08:03 824745                         /lib64/libpthread-2.12.so

36bb817000-36bba17000 ---p 00017000 08:03 824745                         /lib64/libpthread-2.12.so

36bba17000-36bba18000 r--p 00017000 08:03 824745                         /lib64/libpthread-2.12.so

36bba18000-36bba19000 rw-p 00018000 08:03 824745                         /lib64/libpthread-2.12.so

36bba19000-36bba1d000 rw-p 00000000 00:00 0

36bc000000-36bc007000 r-xp 00000000 08:03 824746                         /lib64/librt-2.12.so

36bc007000-36bc206000 ---p 00007000 08:03 824746                         /lib64/librt-2.12.so

36bc206000-36bc207000 r--p 00006000 08:03 824746                         /lib64/librt-2.12.so

36bc207000-36bc208000 rw-p 00007000 08:03 824746                         /lib64/librt-2.12.so

36c2000000-36c2016000 r-xp 00000000 08:03 824759                         /lib64/libgcc_s-4.4.6-20120305.so.1

36c2016000-36c2215000 ---p 00016000 08:03 824759                         /lib64/libgcc_s-4.4.6-20120305.so.1

36c2215000-36c2216000 rw-p 00015000 08:03 824759                         /lib64/libgcc_s-4.4.6-20120305.so.1

36c5000000-36c50e8000 r-xp 00000000 08:03 270925                         /usr/lib64/libstdc++.so.6.0.13

36c50e8000-36c52e8000 ---p 000e8000 08:03 270925                         /usr/lib64/libstdc++.so.6.0.13

36c52e8000-36c52ef000 r--p 000e8000 08:03 270925                         /usr/lib64/libstdc++.so.6.0.13

36c52ef000-36c52f1000 rw-p 000ef000 08:03 270925                         /usr/lib64/libstdc++.so.6.0.13

36c52f1000-36c5306000 rw-p 00000000 00:00 0

36c9400000-36c945d000 r-xp 00000000 08:03 824769                         /lib64/libfreebl3.so

36c945d000-36c965c000 ---p 0005d000 08:03 824769                         /lib64/libfreebl3.so

36c965c000-36c965d000 r--p 0005c000 08:03 824769                         /lib64/libfreebl3.so

36c965d000-36c965e000 rw-p 0005d000 08:03 824769                         /lib64/libfreebl3.so

36c965e000-36c9662000 rw-p 00000000 00:00 0

36c9c00000-36c9c07000 r-xp 00000000 08:03 824770                         /lib64/libcrypt-2.12.so

36c9c07000-36c9e07000 ---p 00007000 08:03 824770                         /lib64/libcrypt-2.12.so

36c9e07000-36c9e08000 r--p 00007000 08:03 824770                         /lib64/libcrypt-2.12.so

36c9e08000-36c9e09000 rw-p 00008000 08:03 824770                         /lib64/libcrypt-2.12.so

36c9e09000-36c9e37000 rw-p 00000000 00:00 0

7ff00c000000-7ff00c05f000 rw-p 00000000 00:00 0

7ff00c05f000-7ff010000000 ---p 00000000 00:00 0

7ff014000000-7ff014021000 rw-p 00000000 00:00 0

7ff014021000-7ff018000000 ---p 00000000 00:00 0

7ff018000000-7ff018021000 rw-p 00000000 00:00 0

7ff018021000-7ff01c000000 ---p 00000000 00:00 0

7ff01c000000-7ff01c021000 rw-p 00000000 00:00 0

7ff01c021000-7ff020000000 ---p 00000000 00:00 0

7ff020dfb000-7ff020dfc000 ---p 00000000 00:00 0

7ff020dfc000-7ff0217fc000 rw-p 00000000 00:00 0

7ff0217fc000-7ff0217fd000 ---p 00000000 00:00 0

7ff0217fd000-7ff0221fd000 rw-p 00000000 00:00 0

7ff0221fd000-7ff0221fe000 ---p 00000000 00:00 0

7ff0221fe000-7ff022bfe000 rw-p 00000000 00:00 0

7ff022bfe000-7ff022bff000 ---p 00000000 00:00 0

7ff022bff000-7ff0235ff000 rw-p 00000000 00:00 0

7ff0235ff000-7ff023600000 ---p 00000000 00:00 0

7ff023600000-7ff024000000 rw-p 00000000 00:00 0

7ff024000000-7ff024085000 rw-p 00000000 00:00 0

7ff024085000-7ff028000000 ---p 00000000 00:00 0

7ff028109000-7ff02810a000 ---p 00000000 00:00 0

7ff02810a000-7ff028b0a000 rw-p 00000000 00:00 0

7ff028b0a000-7ff028b0b000 ---p 00000000 00:00 0

7ff028b0b000-7ff02950b000 rw-p 00000000 00:00 0

7ff02950b000-7ff02950c000 ---p 00000000 00:00 0

7ff02950c000-7ff029f0d000 rw-p 00000000 00:00 0

7ff029f0d000-7ff029f0e000 ---p 00000000 00:00 0

7ff029f0e000-7ff02ab13000 rw-p 00000000 00:00 0

7ff02ab19000-7ff02ab1a000 ---p 00000000 00:00 0

7ff02ab1a000-7ff02ab5a000 rw-p 00000000 00:00 0

7ff02ab5a000-7ff02ab5b000 r-xp 00000000 08:03 394342                     /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/lib/plugin/test_add.so

7ff02ab5b000-7ff02ad5a000 ---p 00001000 08:03 394342                     /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/lib/plugin/test_add.so

7ff02ad5a000-7ff02ad5b000 rw-p 00000000 08:03 394342                     /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/lib/plugin/test_add.so

7ff02ad5b000-7ff02ad5c000 ---p 00000000 00:00 0

7ff02ad5c000-7ff02ad9c000 rw-p 00000000 00:00 0

7ff02ad9c000-7ff02ad9d000 ---p 00000000 00:00 0

7ff02ad9d000-7ff02b79d000 rw-p 00000000 00:00 0

7ff02b79d000-7ff02b79e000 ---p 00000000 00:00 0

7ff02b79e000-7ff02c19e000 rw-p 00000000 00:00 0

7ff02c19e000-7ff02c19f000 ---p 00000000 00:00 0

7ff02c19f000-7ff02cb9f000 rw-p 00000000 00:00 0

7ff02cb9f000-7ff02cba0000 ---p 00000000 00:00 0

7ff02cba0000-7ff02d5a0000 rw-p 00000000 00:00 0

7ff02d5a0000-7ff02d5a1000 ---p 00000000 00:00 0

7ff02d5a1000-7ff02dfa1000 rw-p 00000000 00:00 0

7ff02dfa1000-7ff02dfa2000 ---p 00000000 00:00 0

7ff02dfa2000-7ff02e9a2000 rw-p 00000000 00:00 0

7ff02e9a2000-7ff02e9a3000 ---p 00000000 00:00 0

7ff02e9a3000-7ff02f3a3000 rw-p 00000000 00:00 0

7ff02f3a3000-7ff02f3a4000 ---p 00000000 00:00 0

7ff02f3a4000-7ff02fda4000 rw-p 00000000 00:00 0

7ff02fda4000-7ff02fda5000 ---p 00000000 00:00 0

7ff02fda5000-7ff0307a5000 rw-p 00000000 00:00 0

7ff0307a5000-7ff0307a6000 ---p 00000000 00:00 0

7ff0307a6000-7ff033c5b000 rw-p 00000000 00:00 0

7ff033c5b000-7ff033c60000 r-xp 00000000 08:03 423032                     /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/lib/plugin/validate_password.so

7ff033c60000-7ff033e60000 ---p 00005000 08:03 423032                     /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/lib/plugin/validate_password.so

7ff033e60000-7ff033e61000 rw-p 00005000 08:03 423032                     /usr/local/mysql-5.6.27-linux-glibc2.5-x86_64/lib/plugin/validate_password.so

7ff033e61000-7ff03475e000 rw-p 00000000 00:00 0

7ff03475e000-7ff03476a000 r-xp 00000000 08:03 786463                     /lib64/libnss_files-2.12.so

7ff03476a000-7ff03496a000 ---p 0000c000 08:03 786463                     /lib64/libnss_files-2.12.so

7ff03496a000-7ff03496b000 r--p 0000c000 08:03 786463                     /lib64/libnss_files-2.12.so

7ff03496b000-7ff03496c000 rw-p 0000d000 08:03 786463                     /lib64/libnss_files-2.12.so

7ff03498c000-7ff04dd0f000 rw-p 00000000 00:00 0

7ff04dd0f000-7ff04dd92000 r-xp 00000000 08:03 824757                     /lib64/libm-2.12.so

7ff04dd92000-7ff04df91000 ---p 00083000 08:03 824757                     /lib64/libm-2.12.so

7ff04df91000-7ff04df92000 r--p 00082000 08:03 824757                     /lib64/libm-2.12.so

7ff04df92000-7ff04df93000 rw-p 00083000 08:03 824757                     /lib64/libm-2.12.so

7ff04df93000-7ff04df95000 rw-p 00000000 00:00 0

7ff04dfaf000-7ff04dfb6000 rw-p 00000000 00:00 0

7fff0b6de000-7fff0b6f3000 rw-p 00000000 00:00 0                          [stack]

7fff0b750000-7fff0b751000 r-xp 00000000 00:00 0                          [vdso]

ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

UDF 编写自定函数的更多相关文章

  1. java mysql自定义函数UDF之调用c函数

    正如sqlite可以定义自定义函数,它是通过API定义c函数的,不像其他,如这里的mysql.sqlite提供原生接口就可以方便的调用其他语言的方法,同样的mysql也支持调用其它语言的方法. goo ...

  2. C#调用C++编写的DLL函数, 以及各种类型的参数传递 （转载）

        C#调用C++编写的DLL函数, 以及各种类型的参数传递 1. 如果函数只有传入参数,比如: C/C++ Code Copy Code To Clipboard //C++中的输出函数 int ...

  3. C#动态调用C++编写的DLL函数

    C#动态调用C++编写的DLL函数 动态加载DLL需要使用Windows API函数:LoadLibrary.GetProcAddress以及FreeLibrary.我们可以使用DllImport在C ...

  4. SQL Server中的CLR编程——用.NET为SQL Server编写存储过程和函数

    原文:SQL Server中的CLR编程--用.NET为SQL Server编写存储过程和函数 很早就知道可以用.NET为SQL Server2005及以上版本编写存储过程.触发器和存储过程的,不过之 ...

  5. 给定一个英文字符串,请编写一个PHP函数找出这个字符串中首先出现三次的那个英文字符(需要区分大小写)，并返回

    给定一个英文字符串,请编写一个PHP函数找出这个字符串中首先出现三次的那个英文字符(需要区分大小写),并返回 //统计字符串中出现的字符的出现次数 public function strNum(){ ...

  6. 编写一个c函数,该函数给出一个字节中被置为1的位的个数

    请编写一个c函数,该函数给出一个字节中被置为1的位的个数 #include <stdio.h> void fun(char ch) { int i; int temp; int count ...

  7. Spark SQL 用户自定义函数UDF、用户自定义聚合函数UDAF 教程（Java踩坑教学版）

    在Spark中,也支持Hive中的自定义函数.自定义函数大致可以分为三种: UDF(User-Defined-Function),即最基本的自定义函数,类似to_char,to_date等 UDAF( ...

  8. 用程序集编写clr表值函数：把正则表达式引入数据库中

    正则表达式非常好,但在数据库中就是没有,但可以通过程序集方式扩展 先编写一个dll,标量函数很好写,表值函数麻烦一点 下面是C#代码 using System; using System.Data; ...

  9. 旧文备份:VC中嵌入NASM编写的汇编函数

    在公司开发的RT下没法使用C库,并且替代库函数没有几个,需要用到setjmp和longjmp函数,没办法,只能自己想办法了,上sourceforge淘换到一个小日本的工程,提供这两个函数的替代源码,名 ...

随机推荐

  1. 155. Min Stack

    题目: Design a stack that supports push, pop, top, and retrieving the minimum element in constant time ...

  2. error: 'LOGE' was not declared in this scope

    移植了下HAL,发现编译出现如下错误 error: 'LOGE' was not declared in this scope 比较了一下android4.1的 system/core/include ...

  3. MySQL导入数据非常慢的解决办法

    MySQL导出的SQL语句在导入时有可能会非常非常慢,经历过导入仅45万条记录,竟用了近3个小时.在导出时合理使用几个参数,可以大大加快导入的速度. -e 使用包括几个VALUES列表的多行INSER ...

  4. scaleform mobile sdk for android 多点触摸 修正

    修正 scaleform 的多点触控 (随手一记 给后来的人做个参考) scaleform 版本号 4.2.24 (估计这就是最后一个 移动版的版本了,万年没有更新了) 开始 一直以为 scalefo ...

  5. [Hadoop源码解读]（二）MapReduce篇之Mapper类

    前面在讲InputFormat的时候,讲到了Mapper类是如何利用RecordReader来读取InputSplit中的K-V对的. 这一篇里,开始对Mapper.class的子类进行解读. 先回忆 ...

  6. JAVA - Blowfish加密出现java.security.InvalidKeyException: Illegal key size 解决方案

    最近用java进行一个blowfish的加密算法,但是在我们的eclipse上报出Illegal key size的错误.google后发现原因是:ymmetricDS加密symmetric.prop ...

  7. inno setup 打包

    ; -- Example1.iss -- ; Demonstrates copying files and creating an icon. ; SEE THE DOCUMENTATION FOR ...

  8. SQL Server 2008空间数据应用系列九：使用空间工具(Spatial Tools)导入ESRI格式地图数据

    转自:http://www.cnblogs.com/beniao/archive/2011/03/22/1989310.html 友情提示,您阅读本篇博文的先决条件如下: 1.本文示例基于Micros ...

  9. nginx根据域名做http,https分发

    omcat端口:8080 做好虚拟主机 参照我的另一篇文章nginx端口:80 根据域名分派 在conf/nginx.conf中的http中增加 include www.huozhe.com.conf ...

  10. [POJ1477]Box of Bricks

    Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 19503   Accepted: 7871 Description Litt ...