1、python 编写 UDF

psql -d postgres
CREATE LANGUAGE plpythonu;

create or replace function hello()
returns text
    as $$
import os
return os.path.abspath('.')
$$ language plpythonu;

执行

select hello();

2、C 语言编写 UDF

c 代码

#include "postgres.h"
#include "fmgr.h"
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(add_ab);
Datum
add_ab(PG_FUNCTION_ARGS)
{
        int32 arg_a = PG_GETARG_INT32(0);
        int32 arg_b = PG_GETARG_INT32(1);
        PG_RETURN_INT32(arg_a + arg_b);
}

编译

gcc  -I/usr/local/oushudb-4.7.0.0/include/postgresql/server -fPIC -c cfunc.c
gcc -shared -o cfunc.so cfunc.o

建函数

psql -d postgres
CREATE FUNCTION add(int,int) RETURNS integer AS '/home/gpadmin/cfunc','add_ab' LANGUAGE C STRICT;

执行

select add(1,2);

3、Java 编写 UDF

psql -d postgres

create language pljava;
CREATE FUNCTION getsysprop_udf(VARCHAR)
      RETURNS VARCHAR
      AS 'java.lang.System.getProperty'
LANGUAGE pljava;

执行

Select getsysprop_udf('user.home');