Re: rotate records - Mailing list pgsql-general

From Natasha Galkina
Subject Re: rotate records
Date
Msg-id C2E6BA7FD3442A4C916735460ABB064F563760@bones.invent.psi.com
Whole thread Raw
In response to rotate records  ("Natasha Galkina" <natasha@platsolns.com>)
Responses Re: rotate records  (Michael Fuhr <mike@fuhr.org>)
List pgsql-general
Michael,

Thank you very much for your response.

I tried your solutions but still it looks like it doesn't work when I
delete random records.

select * from foo;
 id | val
----+-----
  1 | 13
  2 | 14
  3 | 15
(3 rows)

delete from foo where val = '13';
DELETE 1
delete from foo where val = '15';
DELETE 1

select * from foo;
 id | val
----+-----
  2 | 14
(1 row)

insert into foo (val) values ('16');
INSERT 34533 1
psimc_db=# select * from foo;
 id | val
----+-----
  2 | 14
  1 | 16
(2 rows)

insert into foo (val) values ('17');
INSERT 34534 1
psimc_db=#
psimc_db=# select * from foo;
 id | val
----+-----
  1 | 16
  2 | 17

As you can see the record with value '14' is gone without explicit
delete, which is not what I expected. Do you have any ideas on how to
avoid this?

Natasha Galkina.

-----Original Message-----
From: pgsql-general-owner@postgresql.org
[mailto:pgsql-general-owner@postgresql.org] On Behalf Of Michael Fuhr
Sent: Saturday, February 25, 2006 10:39 AM
To: Natasha Galkina
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] rotate records

On Sat, Feb 25, 2006 at 10:12:38AM -0700, Michael Fuhr wrote:
> > If it is not correct, how can I rotate the records in the table?
>
> One way would be to use a trigger to delete records having the same
> event_id as the record being inserted.

I should mention that with the example I posted you can still get
duplicate key violations if enough concurrent transactions insert
into the table at the same time.  I'll have to think a little more
about the best way to avoid that.

--
Michael Fuhr

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