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'); > CREATE TYPE > # BEGIN; > 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)?
