Re: Alter or rename enum value

Matthias Kurz <m.kurz@irregular.at>

From: Matthias Kurz <m.kurz@irregular.at>
To: pgsql-hackers@postgresql.org
Date: 2016-03-24T19:00:09Z
Lists: pgsql-hackers
>
> ilmari@ilmari.org (Dagfinn Ilmari Mannsåker) writes:
>
> >
> > I was bored and thought "how hard could it be?", and a few hours'
> > hacking later, I have something that seems to work.  It doesn't do IF
> > NOT EXISTS yet, and the error messaging could do with some improvement,
> > and there are no docs.  The patch is attached, as well as at
> > https://github.com/ilmari/postgres/commit/enum-alter-value
>
> I've added it to the 2016-09 commitfest as well:
> https://commitfest.postgresql.org/10/588/


Nice! Thank you!

Actually you still miss a "DROP VALUE" action. Also please make sure this
also works when altering an existing enum within a new transaction -
otherwise it does not really make sense (Usually someone wants to alter
existing enums, not ones that have just been created).

As a result a script like this should pass without problems:
-- ### script start
CREATE TYPE bogus AS ENUM('dog');

-- TEST 1:
BEGIN;
ALTER TYPE bogus ADD VALUE 'cat'; -- fails in 9.5 because of the
transaction but should work in future
COMMIT;

-- TEST 2:
BEGIN;
ALTER TYPE bogus RENAME TO bogon;
ALTER TYPE bogon ADD VALUE 'horse'; -- fails in 9.5 because of the
transaction but should work in future
COMMIT;

-- TEST 3:
BEGIN;
ALTER TYPE bogon ALTER VALUE 'dog' TO 'pig'; -- not implemented in 9.5 but
should work in future
ROLLBACK;

-- TEST 4:
BEGIN;
ALTER TYPE bogon DROP VALUE 'cat'; -- not implemented in 9.5 but should
work in future
ROLLBACK;
-- ### script end

End result of enum "bogon" (which was named "bogus" at the beginning of the
script):
-- ###
pig
horse
-- ###

Thank you!

Commits

  1. Relax transactional restrictions on ALTER TYPE ... ADD VALUE (redux).

  2. Partially restore comments discussing enum renumbering hazards.

  3. Allow adding values to an enum type created in the current transaction.