DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 1';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  RAISE NOTICE 'value: %', value(u);

  u := next(u);
  RAISE NOTICE 'value: %', value(u);
END
$$;
NOTICE:  Iteration test 1
NOTICE:  value: Hello World
NOTICE:  value: Hello All
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 3';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  u := next(u);
  u := next(u);
  u := prev(u);
  RAISE NOTICE 'value: %', value(u);
END
$$;
NOTICE:  Iteration test 3
NOTICE:  value: Hello All
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 4';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  u := next(u);
  u := next(u);
  u := first(u);
  RAISE NOTICE 'value: %', value(u);
END
$$;
NOTICE:  Iteration test 4
NOTICE:  value: Hello World
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 5';
  u['aaa'] := 'Hello World';

  RAISE NOTICE 'isnull: %', isnull(u);
  u := next(u);
  RAISE NOTICE 'isnull: %', isnull(u);
END
$$;
NOTICE:  Iteration test 5
NOTICE:  isnull: f
NOTICE:  isnull: t
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 6';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  u := first(u);
  WHILE NOT isnull(u) LOOP
    RAISE NOTICE 'value: %', value(u);
    u := next(u);
  END LOOP;
END
$$;
NOTICE:  Iteration test 6
NOTICE:  value: Hello World
NOTICE:  value: Hello All
NOTICE:  value: Hi
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 7';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  u := first(u);
  WHILE NOT isnull(u) LOOP
    RAISE NOTICE 'value: %', value(u);
    u := next(u);
  END LOOP;

  RAISE NOTICE 'value: %', u['bbb'];
END
$$;
NOTICE:  Iteration test 7
NOTICE:  value: Hello World
NOTICE:  value: Hello All
NOTICE:  value: Hi
NOTICE:  value: Hello All
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 8';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  u := delete(u, 'bbb');

  u := first(u);
  WHILE NOT isnull(u) LOOP
    RAISE NOTICE 'value: %', value(u);
    u := next(u);
  END LOOP;
END
$$;
NOTICE:  Iteration test 8
NOTICE:  value: Hello World
NOTICE:  value: Hi
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 9';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  u := delete(u, 'aaa');

  u := first(u);
  WHILE NOT isnull(u) LOOP
    RAISE NOTICE 'value: %', value(u);
    u := next(u);
  END LOOP;
END
$$;
NOTICE:  Iteration test 9
NOTICE:  value: Hello All
NOTICE:  value: Hi
DO $$
DECLARE
  u   collection('text');
  t   text;
BEGIN
  RAISE NOTICE 'Iteration test 10';
  u['ccc'] := '3';
  u['bbb'] := '2';
  u['eee'] := '5';
  u['ddd'] := '4';
  u['aaa'] := '1';

  u := sort(u);
  WHILE NOT isnull(u) LOOP
    RAISE NOTICE 'value: %', value(u);
    u := next(u);
  END LOOP;
END
$$;
NOTICE:  Iteration test 10
NOTICE:  value: 1
NOTICE:  value: 2
NOTICE:  value: 3
NOTICE:  value: 4
NOTICE:  value: 5
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 11';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';

  u := next(u);
  RAISE NOTICE 'value: %', value(u);
  u := next(u);
  RAISE NOTICE 'value: %', value(u);
  u := next(u);
  RAISE NOTICE 'value: %', value(u);
END
$$;
NOTICE:  Iteration test 11
NOTICE:  value: Hello All
NOTICE:  value: <NULL>
NOTICE:  value: <NULL>
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 12';

  u := first(u);
  RAISE NOTICE 'value: %', value(u);
  u := next(u);
  RAISE NOTICE 'value: %', value(u);
END
$$;
NOTICE:  Iteration test 12
NOTICE:  value: <NULL>
NOTICE:  value: <NULL>
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 13';

  u := prev(u);
  RAISE NOTICE 'value: %', value(u);
END
$$;
NOTICE:  Iteration test 13
NOTICE:  value: <NULL>
DO $$
DECLARE
  u   collection('text');
BEGIN
  RAISE NOTICE 'Iteration test 14';
  u['aaa'] := 'Hello World';
  u['bbb'] := 'Hello All';
  u['ccc'] := 'Hi';

  u := next(u);
  u := next(u);
  RAISE NOTICE 'find after next: %', find(u, 'aaa');
END
$$;
NOTICE:  Iteration test 14
NOTICE:  find after next: Hello World