On 9 March 2016 at 20:19, Matthias Kurz <m.k...@irregular.at> wrote:

> Besides not being able to rename enum values there are two other
> limitations regarding enums which would be nice to get finally fixed:
> 1) There is also no possibility to drop a value.
> 2) Quoting the docs (
> http://www.postgresql.org/docs/9.5/static/sql-altertype.html):
> "ALTER TYPE ... ADD VALUE (the form that adds a new value to an enum type)
> cannot be executed inside a transaction block." Example:
> # CREATE TYPE bogus AS ENUM('good');
> # BEGIN;
> # ALTER TYPE bogus ADD VALUE 'bad';
> ERROR:  ALTER TYPE ... ADD cannot run inside a transaction block
> To summarize it:
> For enums to finally be really usable it would nice if we would have (or
> similiar):
> ALTER TYPE name DROP VALUE [ IF EXISTS ] enum_value
> and
> ALTER TYPE name RENAME VALUE [ IF EXISTS ] old_enum_value_name TO
> new_enum_value_name
> And all of the operations (adding, renaming, dropping) should also work
> when done within a new transaction on an enum that existed before that
> transaction.
> I did some digging and maybe following commits are useful in this context:
> 7b90469b71761d240bf5efe3ad5bbd228429278e
> c9e2e2db5c2090a880028fd8c1debff474640f50
> Also there are these discussions where some of the messages contain some
> useful information:
> http://www.postgresql.org/message-id/29f36c7c98ab09499b1a209d48eaa615b7653db...@mail2a.alliedtesting.com
> http://www.postgresql.org/message-id/50324f26.3090...@dunslane.net
> http://www.postgresql.org/message-id/20130819122938.gb8...@alap2.anarazel.de
> Also have a look at this workaround:
> http://en.dklab.ru/lib/dklab_postgresql_enum/
> How high is the chance that given the above information someone will
> tackle these 3 issues/requests in the near future? It seems there were some
> internal chances since the introduction of enums in 8.x so maybe this
> changes wouldn't be that disruptive anymore?
> Regards,
> Matthias
> On 9 March 2016 at 18:13, Tom Lane <t...@sss.pgh.pa.us> wrote:
>> Andrew Dunstan <and...@dunslane.net> writes:
>> > On 03/09/2016 11:07 AM, Tom Lane wrote:
>> >> I have a vague recollection that we discussed this at the time the enum
>> >> stuff went in, and there are concurrency issues?  Don't recall details
>> >> though.
>> > Rings a vague bell, but should it be any worse than adding new labels?
>> I think what I was recalling is the hazards discussed in the comments for
>> RenumberEnumType.  However, the problem there is that a backend could make
>> inconsistent ordering decisions due to seeing two different pg_enum rows
>> under different snapshots.  Updating a single row to change its name
>> doesn't seem to have a comparable hazard, and it wouldn't affect ordering
>> anyway.  So it's probably no worse than any other object-rename situation.
>>                         regards, tom lane
Is there a way or a procedure we can go through to make the these ALTER
TYPE enhancements a higher priority? How do you choose which
features/enhancements to implement (next)?

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