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