Re: How to drop a value from an ENUM?

[Melvin Davidson <melvin6925@xxxxxxxxx>]

On Mon, May 28, 2018 at 11:08 PM, Torsten Förtsch <tfoertsch123@xxxxxxxxx> wrote:

Hi,

I am absolutely sure a certain value of one of my ENUM types is not used in the entire database. Now I am asked to drop that value. Unfortunately, there is no ALTER TYPE DROP VALUE.

On my development box I tried

delete from pg_enum

 where enumtypid='my_type_name'::regtype

   and enumlabel='my_label'

It worked and I could not find any adverse effects.

Given the value is not used anywhere, is this a save command?

Thanks,

Torsten

Well, imho, you should avoid enums at all cost. As you have discovered, enums are hard to
maintain and have long been replaced by Foreign Keys.

With that being said, apparently your command was safe. However, the best way is to do the following.to drop/delete an enum.

1. Determine that the particular enum value is NOT referenced by any column of any table in the database.
2. As a superuser, use the following queries:

SELECT t.typname,
       e.enumlabel,
       e.enumsortorder,
       e.enumtypid
  FROM pg_type t
  JOIN pg_enum e ON e.enumtypid = t.oid
 WHERE t.typtype = 'e'
   AND e.enumlabel = 'your_enum_value'
 ORDER BY 1, e.enumsortorder;


DELETE FROM pg_enum
 WHERE enumtypid = <e.enumtypid from previous query>
   AND enumlabel = 'your_enum_value';

--

Melvin Davidson
Maj. Database & Exploration Specialist
Universe Exploration Command – UXC
Employment by invitation only!