Re: how to alter an enum type

Thanks a lot Gurjeet!  I understanded your suggestion... that seems to
work indeed.  But I really would like to be able to alter the enum type
on the fly, so instead of using enum, I think I'll  just use a "smallint"
type and tie the "possible results" to the application using flags such
as 0, 1, 2, 3 and whatever.. I think it will be easier for me this way.

But thanks a lot anyway!!

On Tue, 25 Dec 2007 23:08:12 -0800
"Gurjeet Singh" <singh.gurjeet@gmail.com> wrote:

> Here's a possible solution (this may take long time if the table is too
> big). The trick is to add a new column with a newly defined datatype, that
> picks up values from the old column. Here's the sample psql script (the
> session output follows after that):
>
> create type possible_answers as enum ( 'yes' , 'no' );
> create table questionnare( Q varchar(256), A possible_answers );
> insert into questionnare values( 'dummy Q1', 'yes' );
> insert into questionnare values( 'dummy Q2', 'no' );
>
> begin;
> create type possible_answers_new as enum ( 'yes' , 'no', 'maybe' );
>
> alter table questionnare rename column A to B;
> alter table questionnare add column A possible_answers_new;
>
> update questionnare set A = B::text::possible_answers_new;
>
> alter table questionnare drop column B;
> commit;
>
> vacuum full questionnare;
>
> \d questionnare
>
> insert into questionnare values( 'dummy Q3', 'maybe' );
>
> select * from questionnare;
>
>
> And here's what the session output looks like:
>
> postgres=# create type possible_answers as enum ( 'yes' , 'no' );
> CREATE TYPE
> postgres=# create table questionnare( Q varchar(256), A possible_answers );
> insert into questionnare values( 'dummy Q1', 'yes' );
> CREATE TABLE
> postgres=# insert into questionnare values( 'dummy Q1', 'yes' );
> begin;
> INSERT 0 1
> postgres=# insert into questionnare values( 'dummy Q2', 'no' );
> INSERT 0 1
> postgres=#
> postgres=# begin;
> BEGIN
> postgres=# create type possible_answers_new as enum ( 'yes' , 'no', 'maybe'
> );
> CREATE TYPE
> postgres=#
> postgres=# alter table questionnare rename column A to B;
> ALTER TABLE
> postgres=# alter table questionnare add column A possible_answers_new;
> ALTER TABLE
> postgres=#
> postgres=# update questionnare set A = B::text::possible_answers_new;
> UPDATE 2
> postgres=#
> postgres=# alter table questionnare drop column B;
> commit;
> ALTER TABLE
> postgres=# commit;
> COMMIT
> postgres=#
> postgres=# vacuum full questionnare;
>
> VACUUM
> postgres=#
> postgres=# \d questionnare
>
>          Table "public.questionnare"
>  Column |          Type          | Modifiers
> --------+------------------------+-----------
>  q      | character varying(256) |
>  a      | possible_answers_new   |
>
> postgres=#
> postgres=# insert into questionnare values( 'dummy Q3', 'maybe' );
> INSERT 0 1
> postgres=#
> postgres=# select * from questionnare;
>     q     |   a
> ----------+-------
>  dummy Q1 | yes
>  dummy Q2 | no
>  dummy Q3 | maybe
> (3 rows)
>
> postgres=#
>
>
> Hope it helps.
> --
> gurjeet[.singh]@EnterpriseDB.com
> singh.gurjeet@{ gmail | hotmail | indiatimes | yahoo }.com
>
> EnterpriseDB       http://www.enterprisedb.com
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>
> Mail sent from my BlackLaptop device
> On Dec 24, 2007 12:48 AM, Henrique Pantarotto < henpa@terra.com.br> wrote:
>
> > Hi,
> >
> > I was wondering how can I alter an ENUM type?  I have created a table
> > like this:
> >
> > create type possible_answers as enum('yes', 'no');
> > create table questions ( question text, answers possible_answers);
> > insert into questions values ('Do you like me?', 'yes');
> >
> > So my question is... How can I change "possible_answers" to enum('yes',
> > 'no', 'maybe')?
> >
> > I tried searching the documentation and mailing list, and I couldn't
> > figure this one out.
> >
> >
> > Thanks!
> >
> >
> >
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 9: In versions below 8.0, the planner will ignore your desire to
> >       choose an index scan if your joining column's datatypes do not
> >       match
> >

--

Henrique Pantarotto <henpa@terra.com.br>

http://henrique.pantarotto.com.br/