proposal 9.4 plpgsql: allows access to call stack from GET DIAGNOSTICS statement

Hello

I propose enhancing GET DIAGNOSTICS statement about new field
PG_CONTEXT. It is similar to GET STACKED DIAGNOSTICS'
PG_EXCEPTION_CONTEXT.

Motivation for this proposal is possibility to get  call stack for
debugging without raising exception.

This code is based on cleaned code from Orafce, where is used four
years without any error reports.

CREATE OR REPLACE FUNCTION public."inner"(integer)
 RETURNS integer
 LANGUAGE plpgsql
AS $function$
declare _context text;
begin
  get diagnostics _context = pg_context;
  raise notice '***%***', _context;
  return 2 * $1;
end;
$function$

postgres=# select outer_outer(10);
NOTICE:  ***PL/pgSQL function "inner"(integer) line 4 at GET DIAGNOSTICS
PL/pgSQL function "outer"(integer) line 3 at RETURN
PL/pgSQL function outer_outer(integer) line 3 at RETURN***
CONTEXT:  PL/pgSQL function "outer"(integer) line 3 at RETURN
PL/pgSQL function outer_outer(integer) line 3 at RETURN
 outer_outer
─────────────
          20
(1 row)

Ideas, comments?

Regards

Pavel Stehule