Re: Primary key data type: integer vs identity

On 4/19/19 1:02 PM, Ken Tanzer wrote:
> On Fri, Apr 19, 2019 at 12:50 PM Adrian Klaver
> <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> wrote:
>
>     On 4/19/19 12:35 PM, Ken Tanzer wrote:
>
>      >
>      > Thanks Adrian.  You are as usual correct.  (I had a bunch of tables
>      > created by a function that I assumed were serial, but were not.)
>      > Identity columns still seem tidier and more manageable.  Can you
>     tell if
>      > the function I referenced would change the ownership or not?
>
>     I believe in 'when it doubt try it, whats the worst that can happen?:)':
>
>
> I agree, and if I had a copy of 10+ running, I probably would have! :)
>
>     <NOTE> I needed to be a superuser to run due to this:
>     ERROR:  permission denied for table pg_depend
>     CONTEXT:  SQL statement "UPDATE pg_depend
>           SET deptype = 'i'
>           WHERE (classid, objid, objsubid) = ('pg_class'::regclass,
>     seqid, 0)
>             AND deptype = 'a'"
>     PL/pgSQL function upgrade_serial_to_identity(regclass,name) line 31 at
>     SQL statement
>
>
>     test=# create table serial_test(id serial, fld_1 text);
>     CREATE TABLE
>     test=# \dp serial_test
>                                       Access privileges
>        Schema |    Name     | Type  | Access privileges | Column
>     privileges |
>     Policies
>     --------+-------------+-------+-------------------+-------------------+----------
>        public | serial_test | table |                   |               
>         |
>     (1 row)
>
>     test=# select upgrade_serial_to_identity('serial_test', 'id');
>        upgrade_serial_to_identity
>     ----------------------------
>
>     (1 row)
>
>     test=# \d serial_test
>                                Table "public.serial_test"
>        Column |  Type   | Collation | Nullable |             Default
>
>     --------+---------+-----------+----------+----------------------------------
>        id     | integer |           | not null | generated by default as
>     identity
>        fld_1  | text    |           |          |
>
>
>     test=# \dp+ serial_test
>                                       Access privileges
>        Schema |    Name     | Type  | Access privileges | Column
>     privileges |
>     Policies
>     --------+-------------+-------+-------------------+-------------------+----------
>        public | serial_test | table |                   |               
>         |
>     (1 row)
>
>
> Maybe I'm missing it, but I'm not really sure what that is supposed to
> be telling me about the ownership of the sequence.
>
> The scenario I'm wondering about is:
>
> Table A owned by User 1, and has column created as serial
> The created sequence is altered to be owned by User 2 (with User 1
> granted select & update)
> upgrade_serial_to_identity applied to Table A
> At that point, who owns the sequence?
>
> I can wait until I've got 10+ running and try it myself, but I thought
> maybe someone would know the answer and be willing to share.



select version();
                                                           version

----------------------------------------------------------------------------------------------------------------------------
  PostgreSQL 11.2 on x86_64-pc-linux-gnu, compiled by gcc (SUSE Linux)
7.3.1 20180323 [gcc-7-branch revision 258812], 64-bit

select session_user, current_user;
  session_user | current_user
--------------+--------------
  aklaver      | aklaver

  create table serial_test(id serial, fld_1 text);
CREATE TABLE

\d

                 List of relations
  Schema |        Name        |   Type   |  Owner
--------+--------------------+----------+----------

public | serial_test        | table    | aklaver
public | serial_test_id_seq | sequence | aklaver



test_(aklaver)> \c - postgres
You are now connected to database "test" as user "postgres".
test_(postgres)# select session_user, current_user;
  session_user | current_user
--------------+--------------
  postgres     | postgres
(1 row)

test_(postgres)# select upgrade_serial_to_identity('serial_test', 'id');
  upgrade_serial_to_identity
----------------------------

(1 row)


                  List of relations
  Schema |        Name        |   Type   |  Owner
--------+--------------------+----------+----------

  public | serial_test        | table    | aklaver
  public | serial_test_id_seq | sequence | aklaver


The function is working directly on the system catalogs and I do not
anything that changes ownership:

  UPDATE pg_depend
     SET deptype = 'i'
     WHERE (classid, objid, objsubid) = ('pg_class'::regclass, seqid, 0)
       AND deptype = 'a';

   -- mark the column as identity column
   UPDATE pg_attribute
     SET attidentity = 'd'
     WHERE attrelid = tbl
       AND attname = col;