Function pgx::fcinfo::direct_function_call

pub unsafe fn direct_function_call<R: FromDatum>(
    func: unsafe fn(_: FunctionCallInfo) -> Datum, 
    args: Vec<Option<Datum>>
) -> Option<R>

As #[pg_extern] functions are wrapped with a different signature, this allows you to directly call them.

This mimics the functionality of Postgres' DirectFunctionCall macros, allowing you to call Rust-defined functions. Unlike Postgres' macros, the directly called function is allowed to return a NULL datum.

You'll just need to account for that when using .try_into() to convert the datum into a rust type.

Note

You must suffix the function name with _wrapper, as shown in the example below.

Safety

This function is unsafe as the underlying function being called is likely unsafe

Examples

use pgx::*;

#[pg_extern]
fn add_two_numbers(a: i32, b: i32) -> i32 {
   a + b
}

fn some_func() {
    let result = unsafe { direct_function_call::<i32>(add_two_numbers_wrapper, vec!(2.into_datum(), 3.into_datum())) };
    let sum = result.expect("function returned null");
    assert_eq!(sum, 5);
}