Re: WIP: RangeTypes

On Fri, 2011-01-28 at 21:52 +0000, Thom Brown wrote:
> > This is not very graceful:
> >
> > postgres=# CREATE TYPE numrange AS RANGE (SUBTYPE=numeric,
> > SUBTYPE_CMP=numeric_cmp);
> > ERROR: duplicate key value violates unique constraint
> > "pg_range_rgnsubtype_index"
> > DETAIL: Key (rngsubtype)=(1700) already exists.

You're right, that should be a much nicer error message.

> > Also, if I try the same, but with a different name for the type, I get
> > the same error. Why does that restriction exist? Can't you have
> > types which happen to use the exact same subtype?

At first, that's how I designed it. Then, I realized that the type
system needs to know the range type from the element type in order for
something like ANYRANGE to work.

There's a workaround though: create a domain over numeric, and then
create a range over mynumeric.

=# create domain mynumeric as numeric;
CREATE DOMAIN
=# create type numrange2 as range (subtype=numeric,
subtype_cmp=numeric_cmp);
ERROR: duplicate key value violates unique constraint
"pg_range_rgnsubtype_index"
DETAIL: Key (rngsubtype)=(1700) already exists.
=# create type numrange2 as range (subtype=mynumeric,
subtype_cmp=numeric_cmp);
CREATE TYPE
=# select range(1.1::mynumeric,2.2::mynumeric);
range
--------------
[ 1.1, 2.2 )
(1 row)

> Also, how do you remove a range type which coincides with a system
> range type. For example:
>
> postgres=# CREATE TYPE numrange AS RANGE (SUBTYPE=interval,
> SUBTYPE_CMP=interval_cmp);
> CREATE TYPE
> postgres=# drop type numrange;
> ERROR: cannot drop type numrange because it is required by the database system
>
> Is this because I shouldn't have been able to create this type in the
> first place?

The types are in two different schemas. It's just as though you created
a table called pg_class.

To drop the one you created, do:
DROP TYPE public.numrange;

Regards,
Jeff Davis