PG编写扩展函数之通过C语言实现

原创

岳麓丹枫 2022-07-12 11:59:35 博主文章分类：PostgreSQL ©著作权

文章标签 sql postgresql #include 文章分类 虚拟化云计算

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实例1:手动编译

编写C文件

test.c

#include "postgres.h" 
#include "fmgr.h"


#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif

PG_FUNCTION_INFO_V1(squares_return_int);

Datum squares_return_int(PG_FUNCTION_ARGS)
{
    int32 arg = PG_GETARG_INT32(0);
    PG_RETURN_INT32(arg * arg);
}

PG_FUNCTION_INFO_V1(add);
Datum add(PG_FUNCTION_ARGS)
{
    int32 a = PG_GETARG_INT32(0);
    int32 b = PG_GETARG_INT32(1);
    PG_RETURN_INT32(a+b);
}

编译C文件

gcc -I`pg_config --includedir-server` -fPIC  -c test.c
gcc -shared test.o -o test.so
cp test.so `pg_config --libdir`

在psql中创建函数

[pgsql@node3 ~]$psql
psql (12.3)
Type "help" for help.

postgres=# create or replace  function func_test_square(int) returns int as '$libdir/test.so', 'squares_return_int' LANGUAGE 'c'  STRICT; 
CREATE FUNCTION
postgres=# create or replace function func_add(int) returns int as '$libdir/test.so', 'add' LANGUAGE 'c'  STRICT; 
CREATE FUNCTION
postgres=# 
postgres=# select func_add(1,2);
 func_add 
----------
        3
(1 row)

postgres=# select func_test_square(2);
 func_test_square 
------------------
                4
(1 row)

实例2:通过Makefile编译

编写C文件 add_func.c

#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);
}

编写Makefile 文件

MODULES = add_func

PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
include $(PGXS)

编译安装

make && make install
[pgsql@node3 ~/test]$make
gcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -O2 -fPIC -I. -I./ -I/postgresql/pgsql-12/include/server -I/postgresql/pgsql-12/include/internal  -D_GNU_SOURCE   -c -o add_func.o add_func.c
gcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -O2 -fPIC add_func.o -L/postgresql/pgsql-12/lib   -Wl,--as-needed -Wl,-rpath,'/postgresql/pgsql-12/lib',--enable-new-dtags  -shared -o add_func.so
[pgsql@node3 ~/test]$make install
/usr/bin/mkdir -p '/postgresql/pgsql-12/lib'
/usr/bin/install -c -m 755  add_func.so '/postgresql/pgsql-12/lib/'

在psql中创建函数 add_ab

create function add_ab(int,int)
        returns int
as '$libdir/add_func','add_ab'
language C strict;
postgres=# select add_ab(1,3);
 add_ab 
--------
      4
(1 row)