Обсуждение: Autovaccum and Full vacuum
Hi Folks
My apologies if this is documented - I could not find it.
Are there circumstances under which an autovacuum will do a "full vacuum"?
I guess what I would really like to know is - is it possible that autovacuum will request a AccessExclusiveLock and if yes, under what circumstances?
Thanks
Regards, Tony
My apologies if this is documented - I could not find it.
Are there circumstances under which an autovacuum will do a "full vacuum"?
I guess what I would really like to know is - is it possible that autovacuum will request a AccessExclusiveLock and if yes, under what circumstances?
Thanks
Regards, Tony
On Wed, May 5, 2010 at 2:28 PM, Tony Day <tonyd@panztel.com> wrote:
IIRC, there was a similar bug in pre 8.3. Which version are you using?
--
Shoaib Mir
http://shoaibmir.wordpress.com/
I guess what I would really like to know is - is it possible that autovacuum will request a AccessExclusiveLock and if yes, under what circumstances?
--
Shoaib Mir
http://shoaibmir.wordpress.com/
Hi Shoaib
Thanks for the response.
Sorry - I forgot to mention that I am using PostgreSQL 8.3.9 on Ubuntu 9.04.
And just to be clear - I am not suggesting that there is a bug in Postgresql :-)
I am just trying to clarify what it does and doesn't do.
Regards, Tony
Thanks for the response.
Sorry - I forgot to mention that I am using PostgreSQL 8.3.9 on Ubuntu 9.04.
And just to be clear - I am not suggesting that there is a bug in Postgresql :-)
I am just trying to clarify what it does and doesn't do.
Regards, Tony
On Wed, May 5, 2010 at 4:34 PM, Shoaib Mir <shoaibmir@gmail.com> wrote:
On Wed, May 5, 2010 at 2:28 PM, Tony Day <tonyd@panztel.com> wrote:IIRC, there was a similar bug in pre 8.3. Which version are you using?
I guess what I would really like to know is - is it possible that autovacuum will request a AccessExclusiveLock and if yes, under what circumstances?
--
Shoaib Mir
http://shoaibmir.wordpress.com/
On Wed, May 5, 2010 at 2:46 PM, Tony Day <tonyd@panztel.com> wrote:
--
Shoaib Mir
http://shoaibmir.wordpress.com/
Hi Shoaib
Thanks for the response.
Sorry - I forgot to mention that I am using PostgreSQL 8.3.9 on Ubuntu 9.04.
And just to be clear - I am not suggesting that there is a bug in Postgresql :-)
I am just trying to clarify what it does and doesn't do.
You can find on docs autovacuum at http://www.postgresql.org/docs/8.3/static/routine-vacuuming.html#AUTOVACUUM
It uses VACUUM and not VACUUM FULL, there shouldn't be a need of VACUUM FULL if you have autovacuum enabled with proper thresholds. There can be an odd case where you might have to make auto-vacuum a little more aggressive for a specific table.
Shoaib Mir
http://shoaibmir.wordpress.com/
On Wed, May 5, 2010 at 12:01 AM, Shoaib Mir <shoaibmir@gmail.com> wrote: > On Wed, May 5, 2010 at 2:46 PM, Tony Day <tonyd@panztel.com> wrote: >> >> Hi Shoaib >> >> Thanks for the response. >> >> Sorry - I forgot to mention that I am using PostgreSQL 8.3.9 on Ubuntu >> 9.04. >> And just to be clear - I am not suggesting that there is a bug in >> Postgresql :-) >> I am just trying to clarify what it does and doesn't do. >> >> > > You can find on docs autovacuum > at http://www.postgresql.org/docs/8.3/static/routine-vacuuming.html#AUTOVACUUM > It uses VACUUM and not VACUUM FULL, there shouldn't be a need of VACUUM FULL > if you have autovacuum enabled with proper thresholds. There can be an odd > case where you might have to make auto-vacuum a little more aggressive for a > specific table. autovacuum never executes VACUUM FULL, but... in 8.3, sometimes it finds a page that is empty so it truncate it to release space, and that needs an stronger lock than the normal it uses (but i don't remember exactly what type of lock) and when the autovacuum is executing for anti wraparound problems it cannot be cancelled... so, if an autovacuum execute vacuum for anti wraparound problems and it finds empty pages that should be truncated then you get a situation where a table is locked and you can't terminate the vacuum, if the table is big there are problems... no idea if this happens in 8.4 -- Jaime Casanova www.2ndQuadrant.com Soporte y capacitación de PostgreSQL