Re: WIP: extensible enums

On 16 October 2010 18:25, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> wrote:
> Are there corner cases the author has failed to consider?
>
> None that I could find.
>
> Are there any assertion failures or crashes?
>

I just thought of another corner case, which can lead to a crash. The
comparison code assumes that the number of elements in the enumeration
is constant during a query, but that's not necessarily the case. For
example the following will crash it:

CREATE TYPE test_enum AS ENUM('Elem 1');

CREATE OR REPLACE FUNCTION test_fn(a int) RETURNS test_enum AS
$$
DECLARE
new_label text;
BEGIN
new_label := 'Elem '||a;
EXECUTE 'ALTER TYPE test_enum ADD '''||new_label||''' BEFORE ''Elem 1''';
RETURN new_label::test_enum;
END;
$$
LANGUAGE plpgsql;

WITH t(a) AS (SELECT test_fn(i) FROM generate_series(2, 10) g(i))
SELECT MAX(a) from t;

Of course that's a pathalogical example, but we should protect against
it, preferrably without compromising performance in more normal cases.

Regards,
Dean