From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
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To: | Elein <elein(at)varlena(dot)com> |
Cc: | GENERAL <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: enum bug |
Date: | 2016-03-11 23:45:56 |
Message-ID: | CAKFQuwY-8Lgbp08agWErzjOKF+2qhJ2n_y61b++OovLRNmJuGQ@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
On Fri, Mar 11, 2016 at 4:19 PM, Elein <elein(at)varlena(dot)com> wrote:
> An unused (yet) enum type cannot display the enum ranges. An empty table
> containing that type cannot display enum ranges.
>
Yes, it can.
CREATE TYPE rainbow AS enum ('red','orange','yellow','blue','purple');
SELECT enum_range(null::rainbow);
enum_range
{red,orange,yellow,blue,purple}
I get the distinction between classes and objects. But in many cases, like
this one, you need to obtain an instance of a class - a null is generally
sufficient - and pass that instance to a function. The function can then
use "pg_typeof(instance_value)::oid" to derive the oid for the
corresponding class. This is a common idiom in PostgreSQL.
The only improvement, besides the error handling point, that I see to be
had here is your understanding of how the system works.
David J.
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