Search Postgresql Archives

RE: Are my autovacuum settings too aggressive for this table?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Michael Lewis <mlewis@xxxxxxxxxxx> writes:
>My thinking is opposite from what you have. I consider it important to very aggressive on autovacuum because it only ever does the required amount of >work. If a tiny amount of work is needed, it does only that and is done. Assuming it doesn't cause I/O concerns, do it as often as possible to minimize the> growth of bloat and maximize the reuse of the space already allocated to that relation.

Excellent, I am not seeing any I/O concerns, and it seems to be keeping up now, so I will keep this setting unless someone else points out another suggestion.

>On the subject of analyze, the statistics are unlikely to be impacted significantly by inserting about 24k rows to a table with almost 20 million already. >With default_statistics_target at 100, what are the chances those new rows will even be included in the sample? I don't know the math, but given each >run of analyze does the same ALL the work each and every time it runs, it seems prudent to do them a little less often than autovacuum anyway. >Regardless though, autoanalyze is a small amount of work that it does each time.

I agree, this is excellent advice, I overlooked the fact that this is a sample and the new rows may not even be included in this sample.  I will adjust accordingly.


-----Original Message-----
From: Jason Ralph <jralph@xxxxxxxxxxxxxxxxxxxxx>
Sent: Friday, November 1, 2019 2:59 PM
To: pgsql-general@xxxxxxxxxxxxxxxxxxxx
Cc: Jason Ralph <jralph@xxxxxxxxxxxxxxxxxxxxx>
Subject: Are my autovacuum settings too aggressive for this table?

Hello list,

DB1=# select version();
-[ RECORD 1 ]----------------------------------------------------------------------------------------------------
version | PostgreSQL 11.5 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-23), 64-bit


I am sure this question has come up before, I have scoured the documentation and I think I have a good grasp on the autovacuum.  I wanted to ask the team if my settings for this particular table are too aggressive, I have the following set which is producing a vacuum analyze multiple times a day.

I think the defaults out of the box were not aggressive enough, so I went with the following on the global level, I will possibly move to table level if needed.  I tried to show the stats below of a 10 minute interval during peak time. Any push in the right direction is appreciated, I want my tables analyzed and vacuumed but do not want to over do it. The rest of the autovacuum settings are default.

I know the stats are estimates so here is my calculations.

Live tuples = 19,766,480
Analyze scale factor = 0.001
Analyze thresh = 5000
Thresh + live_tuples * factor = 24,766

So an autovacuum analyze should trigger around 24K tuples modified, is this to little or too much? Same goes for autvacuum vacuum, is it too aggressive?

#------------------------------------------------------------------------------
# AUTOVACUUM
#------------------------------------------------------------------------------
autovacuum_naptime = 1h
autovacuum_vacuum_threshold = 10000
autovacuum_analyze_threshold = 5000
autovacuum_vacuum_scale_factor = 0.002
autovacuum_analyze_scale_factor = 0.001




DB1=# \x
Expanded display is on.
DB1=# select now();
-[ RECORD 1 ]----------------------
now | 2019-11-01 14:35:51.893328-04

DB1=# select * from pg_stat_user_tables where relname = 'members'; -[ RECORD 1 ]-------+------------------------------
relid               | 18583
schemaname          | public
relname             | members
seq_scan            | 129
seq_tup_read        | 2036932707
idx_scan            | 546161742
idx_tup_fetch       | 1670607103
n_tup_ins           | 46742
n_tup_upd           | 35704112
n_tup_del           | 0
n_tup_hot_upd       | 31106485
n_live_tup          | 19766480
n_dead_tup          | 1844251
n_mod_since_analyze | 15191
last_vacuum         | 2019-10-13 15:42:06.043385-04
last_autovacuum     | 2019-11-01 12:24:45.575283-04
last_analyze        | 2019-10-13 15:42:17.370086-04
last_autoanalyze    | 2019-11-01 12:25:17.181133-04
vacuum_count        | 2
autovacuum_count    | 15
analyze_count       | 2
autoanalyze_count   | 17

DB1=# select now();
-[ RECORD 1 ]----------------------
now | 2019-11-01 14:45:10.845269-04

DB1=# select * from pg_stat_user_tables where relname = 'members'; -[ RECORD 1 ]-------+------------------------------
relid               | 18583
schemaname          | public
relname             | members
seq_scan            | 129
seq_tup_read        | 2036932707
idx_scan            | 546171120
idx_tup_fetch       | 1670615505
n_tup_ins           | 46742
n_tup_upd           | 35705068
n_tup_del           | 0
n_tup_hot_upd       | 31107303
n_live_tup          | 19766480
n_dead_tup          | 1844881
n_mod_since_analyze | 16147
last_vacuum         | 2019-10-13 15:42:06.043385-04
last_autovacuum     | 2019-11-01 12:24:45.575283-04
last_analyze        | 2019-10-13 15:42:17.370086-04
last_autoanalyze    | 2019-11-01 12:25:17.181133-04
vacuum_count        | 2
autovacuum_count    | 15
analyze_count       | 2
autoanalyze_count   | 17

Thanks for your time,
Jason Ralph

This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any errors or omissions in the contents of this message, which arise as a result of e-mail transmission. If verification is required please request a hard-copy version.






[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]

  Powered by Linux