Re: BUG #5492: Sequence corruption

Hi Greg,

first of all thank you for your answer below.

The first problem of the query performing slowly has been solved with a
FULL VACUUMING of the database.
Now the problem of the sequence remains.

This e-mail is sent to pgsql-general(at)postgresql(dot)org e-mail address too, as
per your suggestion.

WIth reference to the "bad" sequence, if I use pgAdmin III and go to
subject_isid_seq object of the business schema I see the following:

-- Sequence: business.subject_isid_seq

-- DROP SEQUENCE business.subject_isid_seq;

CREATE SEQUENCE business.subject_isid_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 9223372036854775807
START 47948992
CACHE 10;
ALTER TABLE business.subject_isid_seq OWNER TO netdw_owner;

My problem is that the START value is higher than the MAX value (100) used
in the table. I tried to change the START value with SETVAL function many
times without success.
With the above situation if I now try to change the value esecuting the
following code:

SELECT SETVAL('business.subject_isid_seq', MAX(iSId)) FROM
business.Subject;

I obtain the return value 100, as expected.
If I now use pgAdmin III to look at the sequence data I see the following
situation:

CREATE SEQUENCE business.subject_isid_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 9223372036854775807
START 1810
CACHE 10;
ALTER TABLE business.subject_isid_seq OWNER TO netdw_owner;

Every time I try to change the value to 100 I see the value is different.
When I execute the SETVAL function I am connected as netdw_owner user,
that's the business schema owner. So I believe it's not a problem of
object ownership.
I have other sequences in my database but only this one has this problem.

Could anybody help me in finding a solution?
Thank you very much in advance.

Piergiorgio Buongiovanni

Greg Stark <gsstark(at)mit(dot)edu>
07/06/2010 23.33

Per
Piergiorgio Buongiovanni <piergiorgio(dot)buongiovanni(at)netspa(dot)it>
CC
pgsql-bugs(at)postgresql(dot)org
Oggetto
Re: BUG #5492: Query performs slowly and sequence corrupted

On Mon, Jun 7, 2010 at 5:36 PM, Piergiorgio Buongiovanni
<piergiorgio(dot)buongiovanni(at)netspa(dot)it> wrote:
> I reused the previous command to re-set the sequence value to the right
one,
> but I see that the START value is now 59100. I reused the previous
command
> another time and the START value is now 30440.
>
> I think this is a bug. I have a lot of problems with this sequence.

Sequences wouldn't directly affect retrieval times. But one way you
could get both of these symptoms is by having an application which
inserts many rows but aborts and rolls back the inserts without
committing. Perhaps a large copy which is interrupted. That would fill
the table with garbage dead records which could slow down retrieval
depending on the access method and also increase the sequence value.

You'll need to provide a lot more data before people would be able to
help you. I suggest you post the results of "explain analyze select
..." as well as some details of what previous operations you've done
on this database to pgsql-general(at)postgresql(dot)org(dot) pgsql-bugs is not
really appropriate unless you're reporting a specific problem with
postgresql in general, not an operational problem with your database.

--
greg

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