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AW: AW: [Extern] Re: autovacuum on pg_catalog tables

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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@xxxxxxxxxx>
Gesendet: Freitag, 4. Juni 2021 17:44
An: Vijaykumar Jain <vijaykumarjain.github@xxxxxxxxx>
Cc: pgsql-general@xxxxxxxxxxxxxxxxxxxx
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@xxxxxxxxx>
Gesendet: Freitag, 4. Juni 2021 17:37
An: Zwettler Markus (OIZ) <Markus.Zwettler@xxxxxxxxxx>
Cc: pgsql-general@xxxxxxxxxxxxxxxxxxxx
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@xxxxxxxxxx> 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


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