Re: WIP: extensible enums

Josh Berkus wrote:
> On 8/23/10 12:20 PM, Tom Lane wrote:
> > Josh Berkus <josh@agliodbs.com> writes:
> >> I really don't see the value in making a command substantially less
> >> intuitive in order to avoid a single keyword, unless it affects areas of
> >> Postgres outside of this particular command.
> > 
> > It's the three variants to do two things that I find unintuitive.
> 
> Actually, it's 3 different things:
> 
> 1. BEFORE adds a value before the value cited.
> 2. AFTER adds a value after the value cited.
> 3. unqualified adds a value at the end.
> 
> The fact that AFTER allows you to add a value at the end is
> circumstantial overlap.  While executing an AFTER, you wouldn't *know*
> that you were adding it to the end, necessarily.
> 
> The other reason to have AFTER is that, in scripts, the user may not
> have the before value handy due to context (i.e. dynamically building an
> enum).
> 
> Anyway, this'll still be useful with BEFORE only.  I'm just convinced
> that we'll end up adding AFTER in 9.2 or 9.3 after we get a bunch of
> user complaints and questions.  So why not add it now?

CREATE ENUM in PG 9.0 allows you to create an enum with no columns,
e.g.:
test=> CREATE TYPE etest AS ENUM ();CREATE TYPE

so I think we have to have the ability add an enum without a
before/after.  This ability was added for pg_upgrade.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +