原 PostgreSQL用C完成存储过程例子

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

#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
}

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

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

highgo=# load 'myapi';
LOAD

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

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