Re: Primary key data type: integer vs identity

On 4/19/19 11:32 AM, Ken Tanzer wrote:
> On Fri, Apr 19, 2019 at 11:20 AM Adrian Klaver
> <adrian(dot)klaver(at)aklaver(dot)com <mailto:adrian(dot)klaver(at)aklaver(dot)com>> wrote:
>
> On 4/19/19 11:14 AM, Rich Shepard wrote:
> > On Fri, 19 Apr 2019, Adrian Klaver wrote:
> >
> >> If it is working for you now I see no reason to switch.
> >
> > Adrian,
> >
> > It does work. I just learned about the SQL identity type and want
> to learn
> > when it's most appropriate to use. The databases I develop all
> work with
> > integers as primary keys and reading about the type didn't
> clarify (for me)
> > when it should be used.
>
> Mainly for folks that want cross database SQL compliance. It is not a
> type so much as a way of specifying an auto-increment column.
>
>
> It also sounds like it has advantages in terms of tying your sequence
> directly to the column.  If you drop a serial column, it doesn't drop
> the sequence.

Misread your post the first time still:

create table serial_test(id serial, fld_1 text);

CREATE TABLE

test=> \d serial_test

Table "public.serial_test"

Column | Type | Collation | Nullable | Default

--------+---------+-----------+----------+-----------------------------------------

id | integer | | not null |
nextval('serial_test_id_seq'::regclass)

fld_1 | text | | |

test=> alter table serial_test drop column id;

ALTER TABLE

test=> \d serial_test

Table "public.serial_test"

Column | Type | Collation | Nullable | Default

--------+------+-----------+----------+---------

fld_1 | text | | |

test=> select * from serial_test_id_seq ;

ERROR: relation "serial_test_id_seq" does not exist
LINE 1: select * from serial_test_id_seq ;

> Once I've upgraded to 10+, I might look at converting my existing serial
> columns.  Peter Eisentraut wrote a good piece(1) on identity columns,
> including a function for converting existing serial columns.  I've
> copied the function below, but had two questions about it:
>
> 1)  Would the function as written also reassign ownership to that table
> column?  (I see the update to pg_depend and pg_attribute, but don't know
> enough about them to know if that changes ownership)
> 2)  Would one have to be a superuser to do this?
>
> Thanks,
> Ken

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com