[PATCH] GET DIAGNOSTICS FUNCTION_NAME

Hi,

Attached is a patch to implement a feature to get the current function
name by GET DIAGNOSTICS in PL/pgSQL function.

Currentyly, we can get call stack by GET DIAGNOSTICS PG_CONTEXT, but
we cannot get the function name directly. One of our clients wanted
this feature for debugging, and this was realized by creating a
function that extracts the function name string from call stack.
However, the overhead of function calls was not small, and it
caused performance regression.

I found that there are other needs for this feature[1], so I have
implemented this.

[1] https://stackoverflow.com/questions/12611596/getting-name-of-the-current-function-inside-of-the-function-with-plpgsql

Example:

postgres=# CREATE FUNCTION test() RETURNS void
LANGUAGE plpgsql AS $$
DECLARE t text;
BEGIN
GET DIAGNOSTICS t = FUNCTION_NAME;
RAISE INFO 'function name: %', t;
END;
$$;
CREATE FUNCTION

postgres=# select test();
INFO: function name: test()
test
------

(1 row)

Regards,

--
Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>