Re: Vacuum Tuning Question

You turned off autovacuum_vacuum_scale_factor!

Murthy Nunna wrote on 5/19/2023 11:35 AM:
>
> Hi,
>
> I have a fairly large database (several TBs) where auto vacuum is
> enabled. My focus is to keep the datfrozenxid reasonably low and avoid
> manual vacuum. When I run following query, I see the percentage
> creeping up every day. Right after running vacuum manually on tables
> with large relfrozenxid the following query would return 7% on pgprd1
> database but after 5 months it increased to 40%. So, eventually I am
> afraid I have to vacuum the tables manually which has its own problems
> like creating massive WALs in a short time etc. I would like to avoid
> manual vacuuming for this reason.
>
> SELECT freez, txns, ROUND(100*(txns/freez::float)) AS perc, datname
>
> FROM (SELECT foo.freez::int, age(datfrozenxid) AS txns, datname
>
> FROM pg_database d JOIN (SELECT setting AS freez FROM pg_settings
> WHERE name = 'autovacuum_freeze_max_age') AS foo
>
> ON (true) WHERE d.datallowconn) AS foo2 ORDER BY 3 DESC, 4 ASC;
>
> 1500000000 | 599260139 |   40 | pgprd1
>
> 1500000000 |  50138249 |    3 | postgres
>
> 1500000000 |  50138249 |    3 | template1
>
> Auto vacuum is working as I can see from logs it is repeatedly
> vacuuming same tables, but I don’t see that as a problem because those
> are the tables that get updated/inserted continuously.
>
> Following are the settings I have. I am wondering if there is a way
> autovacuum  can keep the above “datfrozenxid” low and not keep
> increasing. Thank you ahead time for reading my post.
>
> postgres=# select name, setting, unit from pg_settings where name like
> '%autovacuum%';
>
> name                  |  setting   | unit
>
> ---------------------------------------+------------+------
>
> autovacuum | on         |
>
> autovacuum_analyze_scale_factor | 0.1        |
>
> autovacuum_analyze_threshold | 5000       |
>
> autovacuum_freeze_max_age | 1500000000 |
>
> autovacuum_max_workers | 5          |
>
> autovacuum_multixact_freeze_max_age | 400000000  |
>
> autovacuum_naptime | 60         | s
>
> autovacuum_vacuum_cost_delay | 2          | ms
>
> autovacuum_vacuum_cost_limit | -1         |
>
> autovacuum_vacuum_insert_scale_factor | 0          |
>
> autovacuum_vacuum_insert_threshold | 5000       |
>
> autovacuum_vacuum_scale_factor | 0          |
>
> autovacuum_vacuum_threshold | 5000       |
>
> autovacuum_work_mem | -1         | kB
>
> log_autovacuum_min_duration | 0          | ms
>
> (15 rows)
>

Regards,

Michael Vitale

Michaeldba(at)sqlexec(dot)com <mailto:michaelvitale(at)sqlexec(dot)com>

703-600-9343