--
-- $_SHARED: a Hash persisting across calls within a session.
--
CREATE FUNCTION set_shared(text, text) RETURNS void LANGUAGE plruby AS $$
    $_SHARED[args[0]] = args[1]
    nil
$$;
CREATE FUNCTION get_shared(text) RETURNS text LANGUAGE plruby AS $$
    $_SHARED[args[0]]
$$;
SELECT set_shared('key', 'value');
 set_shared 
------------
 
(1 row)

SELECT get_shared('key');
 get_shared 
------------
 value
(1 row)

SELECT get_shared('missing') IS NULL AS missing_is_null;
 missing_is_null 
-----------------
 t
(1 row)

-- Arbitrary Ruby objects survive between calls.
CREATE FUNCTION push_shared(int) RETURNS int LANGUAGE plruby AS $$
    ($_SHARED['list'] ||= []) << args[0]
    $_SHARED['list'].length
$$;
SELECT push_shared(10);
 push_shared 
-------------
           1
(1 row)

SELECT push_shared(20);
 push_shared 
-------------
           2
(1 row)

SELECT push_shared(30);
 push_shared 
-------------
           3
(1 row)

-- $_SHARED written before an error survives, and is visible to a later call.
CREATE FUNCTION stash_then_fail() RETURNS int LANGUAGE plruby AS $$
    $_SHARED['survivor'] = 'still here'
    raise 'deliberate failure'
$$;
SELECT stash_then_fail();
ERROR:  deliberate failure
CONTEXT:  PL/Ruby function "stash_then_fail"
SELECT get_shared('survivor');
 get_shared 
------------
 still here
(1 row)