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Message-ID: <6a157286-5948-48ac-bc50-7bb4e65ee5e5@aklaver.com>
Date: Thu, 21 Nov 2024 09:54:30 -0800
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Subject: Re: Database stats ( pg_stat_database.stats_reset ) get reset on
 daily basis - why?
To: Steeve Boulanger <sboulanger29@gmail.com>, pgsql-general@postgresql.org
References: <CAAiSvx8_Z6QGey92dC+6Yona18KDMLWinfR5LOJsMgj-42XJtg@mail.gmail.com>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <CAAiSvx8_Z6QGey92dC+6Yona18KDMLWinfR5LOJsMgj-42XJtg@mail.gmail.com>
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On 11/21/24 09:29, Steeve Boulanger wrote:
> Hello,
> 
> I have noticed recently that our databases (ie most but not all) have 
> their stats reset on daily basis:
> 
> select count(case when stats_reset > (now() - interval '1 day') then 1 
> else null end) db_reset_cnt, count(*) db_total_cnt from pg_stat_database;
>   db_reset_cnt | db_total_cnt
> --------------+--------------
>             77 |          157
> 
> Furthermore, the archiver stats also get reset:
> 
> select stats_reset from pg_stat_archiver;
>            stats_reset
> -------------------------------
>   2024-11-21 13:52:35.864855+00
> 
> Some facts:
> - PostgreSQL v13.16 on Linux Ubuntu 20.04
> - There's no evidence in the logs that any pg_stat_reset* functions have 
> been executed
>              name            | setting
> ----------------------------+---------
>   log_min_duration_statement | 0
>   log_statement              | all
> - we don't have any user procs with a pg_stat_reset call
> - the timestamps of the reset across databases are sometimes close to 
> each other, but not always
> Anyone has any insight on what could be doing this daily stats reset, or 
> perhaps how to find the root cause?

https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-STATS-SETUP

"Cumulative statistics are collected in shared memory. Every PostgreSQL 
process collects statistics locally, then updates the shared data at 
appropriate intervals. When a server, including a physical replica, 
shuts down cleanly, a permanent copy of the statistics data is stored in 
the pg_stat subdirectory, so that statistics can be retained across 
server restarts. In contrast, when starting from an unclean shutdown 
(e.g., after an immediate shutdown, a server crash, starting from a base 
backup, and point-in-time recovery), all statistics counters are reset."


> 
> Regards,
> Steeve
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com