Re: Shared buffers increased but cache hit ratio is still 85%

On 07/18/2018 10:43 AM, Andreas Kretschmer wrote:
> 
> 
> Am 18.07.2018 um 10:26 schrieb Hans Schou:
>> Am I doing something wrong or should some history be cleared?
> 
> Reset the stats for that database. You can check the date of last reset
> with:
> 
> select stats_reset from pg_stat_database where datname = 'database_name';
> 
> and reset it with:
> 
> ||pg_stat_reset()
> ||
> ||Reset all statistics counters for the current database to zero
> (requires superuser privileges by default, but EXECUTE for this function
> can be granted to others.)||
> 

It might be better to note current values of the counters somewhere, and
compute a delta later (and use that to compute the cache hit ratio). The
issue is that pg_stat_reset() throws away all sorts of interesting and
important stats, including those driving autovacuum/autoanalyze.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services