目的：用C完成一个存储过程例子，存储过程实现对表某一段进行update。

准备工作

1、安装数据库

2、建立表test

highgo=# create table test(id int,name text,label int);
CREATE TABLE

3、建立C文件,C代码如下：

#include "postgres.h"
#include "executor/spi.h"
#include "utils/builtins.h"
 
#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif
 
int mydelete(int key);
 
int
mydelete(int key)
{
    char command[128];  //视命令长短建立相应大小的数组
    int ret;
    int proc;                       //对表数据操作的行数
 
    /* 将命令赋值到command */
    sprintf(command,"update test set label = 0 where id = %d and label = 1; ",key);
 
    SPI_connect();             //内部链接
    ret = SPI_exec( command,0);  //执行操作
    proc = SPI_processed;       //为行数赋值
    SPI_finish();                //中断连接
    return (proc);               //将操作行数作为返回结果
}

数据库api参考文档：http://www.postgresql.org/docs/9.4/static/spi.html

编译到安装

4、gcc编译

gcc -fpic -I/opt/HighGo/db/20150401/include/postgresql/server/ -shared -o myapi.so myapi.c

5、复制到lib目录下

cp myapi.so /opt/HighGo/db/20150401/lib/postgresql/

6、加载到服务器

highgo=# load 'myapi';
LOAD

7、建立函数

highgo=# create function mydele(integer) returns integer as '$libdir/myapi.so','mydelete' language c strict;
CREATE FUNCTION
highgo=#

8、效果

highgo=# insert into test values (1,'jim',1);
INSERT 0 1
highgo=# insert into test values (2,'tom',1);
INSERT 0 1
highgo=# select * from test;
 id | name | label 
----+------+-------
  1 | jim  |     1
  2 | tom  |     1
 
highgo=# select mydele(1);
 mydele 
--------
      1
(1 row)
highgo=# select * from test;
 id | name | label 
----+------+-------
  2 | tom  |     1
  1 | jim  |     0