https://www.reddit.com/r/golang/comments/1ol2tqv/write_postgresql_functions_in_go_golang_example/


Write PostgreSQL functions in Go Golang example

It took me a while to figure this out. Go compiles the C files automatically.

add_two.c

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


PG_MODULE_MAGIC;


extern int32 Adder(int32);


PG_FUNCTION_INFO_V1(add_two);


Datum
add_two(PG_FUNCTION_ARGS)
{
    int32 arg = PG_GETARG_INT32(0);
    PG_RETURN_INT32(Adder(arg));
}

adder.go

package main


/*
#cgo CFLAGS: -DWIN32 -ID:/pg18headers -ID:/pg18headers/port/win32
#cgo LDFLAGS: -LD:/pg18lib
#include "postgres.h"
#include "fmgr.h"


// Forward declare the C function so cgo compiles add_two.c too.
extern void init_add_two();
*/
import "C"


//export Adder
func Adder(a C.int32) C.int32 {
    return a + 3
}


func main() {}

Compile it

PS D:\C\myextension> go build -o add_two.dll -buildmode=c-shared

In PostgreSQL: open the query window (adjust path to your generated dynamically loaded library and header file (.dll, .h).

CREATE FUNCTION add_two(int4) RETURNS int4

AS 'D:/C/myextension/add_two.dll', 'add_two'

LANGUAGE C STRICT;

And finally test it:

SELECT add_two(10)

Result:
	add_two (integer)
1 	13