Thread: AW: AW: [Extern] Re: autovacuum on pg_catalog tables
I have some hundred (user) tables where only a small subset of them requires a more aggressive autovacuum.
Setting table level parameters on this small subset seems more straightforward to me.
Loosing this setting on pg_dump / pg_upgrade would be ok for me. Doesn't happen that often.
I tried this on postgres 9.6:
postgresql.conf -> allow_system_table_mods=on + pg_ctl restart
# alter table pg_catalog.pg_shdepend set (autovacuum_vacuum_scale_factor = 0, autovacuum_vacuum_threshold = 1000);
ERROR: shared tables cannot be toasted after initdb
Time: 0.618 ms
# alter table pg_catalog.pg_largeobject set (autovacuum_vacuum_scale_factor = 0, autovacuum_vacuum_threshold = 1000);
ERROR: AccessExclusiveLock required to add toast table.
Time: 0.590 ms
# alter table pg_catalog.pg_largeobject_metadata set (autovacuum_vacuum_scale_factor = 0, autovacuum_vacuum_threshold = 1000);
ERROR: AccessExclusiveLock required to add toast table.
Time: 1.601 ms
Any idea?
Thanks, Markus
Von: Zwettler Markus (OIZ) <Markus.Zwettler@zuerich.ch>
Gesendet: Freitag, 4. Juni 2021 17:44
An: Vijaykumar Jain <vijaykumarjain.github@gmail.com>
Cc: pgsql-general@lists.postgresql.org
Betreff: AW: [Extern] Re: autovacuum on pg_catalog tables
Thanks for the info.
I have a lot of LO manipulation and want a more aggressive autovacuum on some pg_catalog tables therefore.
I do not see any reason why this should not work or be at risk?
Markus
Von: Vijaykumar Jain <vijaykumarjain.github@gmail.com>
Gesendet: Freitag, 4. Juni 2021 17:37
An: Zwettler Markus (OIZ) <Markus.Zwettler@zuerich.ch>
Cc: pgsql-general@lists.postgresql.org
Betreff: [Extern] Re: autovacuum on pg_catalog tables
ok, what i am sharing, DO NOT DO IT.
it is just to answer why it is not working :)
postgres=# alter table pg_catalog.pg_largeobject_metadata set (AUTOVACUUM_VACUUM_COST_DELAY = 1);
ERROR: permission denied: "pg_largeobject_metadata" is a system catalog
postgres=# show allow_system_table_mods;
allow_system_table_mods
-------------------------
off
(1 row)
postgres=# set allow_system_table_mods TO 1;
SET
postgres=# show allow_system_table_mods;
allow_system_table_mods
-------------------------
on
(1 row)
postgres=# alter table pg_catalog.pg_largeobject_metadata set (AUTOVACUUM_VACUUM_COST_DELAY = 1);
ALTER TABLE
but you can always run vacuum manually on the table.
vacuum (verbose,analyze) pg_catalog.pg_largeobject_metadata;
INFO: vacuuming "pg_catalog.pg_largeobject_metadata"
INFO: index "pg_largeobject_metadata_oid_index" now contains 0 row versions in 1 pages
DETAIL: 0 index row versions were removed.
0 index pages have been deleted, 0 are currently reusable.
CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s.
INFO: "pg_largeobject_metadata": found 0 removable, 0 nonremovable row versions in 0 out of 0 pages
DETAIL: 0 dead row versions cannot be removed yet, oldest xmin: 8083775
There were 0 unused item identifiers.
Skipped 0 pages due to buffer pins, 0 frozen pages.
0 pages are entirely empty.
CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s.
INFO: analyzing "pg_catalog.pg_largeobject_metadata"
INFO: "pg_largeobject_metadata": scanned 0 of 0 pages, containing 0 live rows and 0 dead rows; 0 rows in sample, 0 estimated total rows
VACUUM
On Fri, 4 Jun 2021 at 20:10, Zwettler Markus (OIZ) <Markus.Zwettler@zuerich.ch> wrote:
I would like to start a more aggressive autovacuum on pg_catalog tables like pg_largeobject.
So I tried as a superuser:
# alter table pg_catalog.pg_largeobject_metadata set (autovacuum_vacuum_scale_factor = 0, autovacuum_vacuum_threshold = 5000);
ERROR: permission denied: "pg_largeobject_metadata" is a system catalog
(How) Is it possible to change such table attributes on pg_catalog tables?
Thanks, Markus
--
Thanks,
Vijay
Mumbai, India
Achtung: Diese E-Mail wurde von einer externen Adresse verschickt. Klicken Sie auf keine Links und öffnen Sie keine angehängten Dateien, wenn Sie den Absender bzw. die Absenderin nicht kennen. Sind Sie sich unsicher, kontaktieren Sie den Service Desk der Stadt Zürich.
"Zwettler Markus (OIZ)" <Markus.Zwettler@zuerich.ch> writes:
> I tried this on postgres 9.6:
> postgresql.conf -> allow_system_table_mods=on + pg_ctl restart
> # alter table pg_catalog.pg_shdepend set (autovacuum_vacuum_scale_factor = 0, autovacuum_vacuum_threshold = 1000);
> ERROR: shared tables cannot be toasted after initdb
> Time: 0.618 ms
> # alter table pg_catalog.pg_largeobject set (autovacuum_vacuum_scale_factor = 0, autovacuum_vacuum_threshold = 1000);
> ERROR: AccessExclusiveLock required to add toast table.
> Time: 0.590 ms
Interesting. FWIW, these examples do seem to work in v12 and up.
Since we don't consider this a supported case, I doubt anyone would
be interested in trying to back-port whatever rearrangement allowed
it to work.
regards, tom lane