Windows上的MySQL UDF开发

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曾以为Windows版本的MySQL存在不能使用UDF的BUG诸提交了一个bug报告。不过
似乎发现是我搞错了，MySQL的技术支持人员给了非常完美的解答，同大家分享
一下。下边是原文回复 :)

Sorry this isn't a bug.
Below I pasted a sample I did sometime ago for another user:

Ok. Assuming you have VC++ and the source distribution and a server
running,
I will create a UDF that returns a name:

Note: the sample is ugly, but the purpose here is to show you how
to handle the UDF.

- Open the mysqld.dsw workspace.
- Add New project to the workspace
- Project name: my_udf
- Select Win32 Dynamic-Link Library
- Click OK
- Select An Empty DLL project
- Click Finish
- Click OK
- Add a new file called my_udf.cpp to the project:

#include <stdlib.h
#include <winsock.h
#include <mysql.h

extern "C" {
char *my_name(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
       char *error);
}

char *my_name(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
       char *error)
{
    char * me = "my name";

    return me;
}

- Type Ctrl+N for to create a new file.
- Select text type
- File name: my_udf.def
- Edit the above file with the below contents:
LIBRARY         UDF_EXAMPLE
DESCRIPTION             'Example Using UDF with VC++'
VERSION         1.0
EXPORTS
        my_name

- Right Click the my_udf project and select Settings
- Click the C/C++ tab
- Select General in the Category Combo
- Add the macro HAVE_DLOPEN to the PreProcessor definition
- Select Preprocessor in the Category Combo
- Add the include path to the text box: Additional Include directories
  e.g: ../include
- Press F7 for to build the DLL.

- Copy the my_udf.dll to the environment path directory:
  winntsystem32 for example.

- Start the mysql client and issue:

C:mysql-udfbinmysql -uroot -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 2 to server version: 3.23.52-max-nt

Type 'help;' or 'h' for help. Type 'c' to clear the buffer.

mysql CREATE FUNCTION my_name RETURNS STRING SONAME "my_udf.dll";
Query OK, 0 rows affected (0.08 sec)

mysql select my_name();

mysql drop function my_name;
Query OK, 0 rows affected (0.00 sec)

画蛇添足的作下简要中文说明。

抱歉，这并不是一个bug。下面我粘贴一个以前为某个客户做的简例，假设你有了
VC++,源码分发，并且有一个正常运行的MySQL服务器。

我将创建一个UDF它将一个名字：
注意：例子非常简陋，目的是让你了解该如何处理手头的UDF。

- 打开 mysqld.dsw 工作区。
- 添加新项目到这个工作区
- Project name: my_udf            // 项目名称:my_udf
- 选择 Win32 Dynamic-Link Library // Win32动态连接库
- 点击 OK
- 选择 An Empty DLL project       // 一个空DLL项目
- 点击 Finish
- 点击 OK
- 添加新文件 my_udf.cpp 到项目中:
#include <stdlib.h
#include <winsock.h
#include <mysql.h

extern "C" {
char *my_name(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
       char *error);
// 兼容C
}

char *my_name(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
       char *error)
{
    char * me = "my name";

    return me;
    // 调用此UDF将返回 my name
}
- 按 Ctrl+N 来创建一个新文件。
- 选择 text 类型
- File name: my_udf.def file://文件名：my_udf.def
- 按照下边的内容编辑文件。
LIBRARY         UDF_EXAMPLE
DESCRIPTION