Re: How to add an INHERITS to an already populated table

On Tue, 31 May 2005, Oleg Bartunov wrote:

> look on pg_inherits table and pg_class.relhassubclass.
> More info http://www.pgsql.ru/db/mw/msg.html?mid=2044343
>

example:

create table t (i int4);
create table t1 (i int4);
create table t2 (i int4);

-- mark 't' has children tables
update pg_class set relhassubclass='t' where relname='t';
-- get oid of child table 't1'
select relfilenode from pg_class where relname='t1';
-- get oid of parent table
select relfilenode from pg_class where relname='t';
-- add inheritance t-t1
insert into pg_inherits values(15769046,15769044,1);
-- get oid of child table 't2'
select relfilenode from pg_class where relname='t2';
-- add inheritance t-t2
insert into pg_inherits values(15769048,15769044,1);

--test
test=# explain analyze select * from t;
                                                   QUERY PLAN
--------------------------------------------------------------------------------------------------------------
  Result  (cost=0.00..88.20 rows=5820 width=8) (actual time=0.057..0.057 rows=0 loops=1)
    ->  Append  (cost=0.00..88.20 rows=5820 width=8) (actual time=0.044..0.044 rows=0 loops=1)
          ->  Seq Scan on t  (cost=0.00..29.40 rows=1940 width=8) (actual time=0.008..0.008 rows=0 loops=1)
          ->  Seq Scan on t1 t  (cost=0.00..29.40 rows=1940 width=8) (actual time=0.007..0.007 rows=0 loops=1)
          ->  Seq Scan on t2 t  (cost=0.00..29.40 rows=1940 width=8) (actual time=0.006..0.006 rows=0 loops=1)
  Total runtime: 0.171 ms
(6 rows)

-- check if alter table works
alter table t add column x real;
test=# \d t
        Table "public.t"
  Column |  Type   | Modifiers
--------+---------+-----------
  i      | integer |
  x      | real    |

test=# \d t1
       Table "public.t1"
  Column |  Type   | Modifiers
--------+---------+-----------
  i      | integer |
  x      | real    |
Inherits: t

test=# \d t2
       Table "public.t2"
  Column |  Type   | Modifiers
--------+---------+-----------
  i      | integer |
  x      | real    |
Inherits: t



>

> On Tue, 31 May 2005, Richard Huxton wrote:
>
>> David Pradier wrote:
>>> Hi everybody,
>>>
>>> is it possible to add some inheritance lively, without doing a
>>> dump/restore ?
>>
>> Not AFAIK. Easiest solution is probably to script some ALTER TABLE ADD
>> COLUMN commands.
>>
>>
>
>     Regards,
>         Oleg
> _____________________________________________________________
> Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
> Sternberg Astronomical Institute, Moscow University (Russia)
> Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
> phone: +007(095)939-16-83, +007(095)939-23-83
>
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>

     Regards,
         Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83