Re: Postgresql 14 performance

On 8/21/22 12:05, Kenny Bachman wrote:
> Hi Team,
>
> Have a lovely Sunday.
> I have a problem with PostgreSQL performance. I am using PostgreSQL
> 14.5 on Linux physical server. My query was taking 1 or 2 seconds
> yesterday, but today it is taking 5-6 seconds. Also, nothing has
> changed in the database. Also, when I run the query for the second
> time, the query runs for the same time, so I expect it to be more
> performant the second time because of the cache.
> (the database cache hit ratio is 97,8)
>
> Lastly, some other queries take milliseconds normally, but sometimes
> they take minutes. I didn't understand why this is happening. (There
> is no lock, no table bloating and up to date analyze)
>
>
> I am adding the explain analyze output as an attachment.

Hi Kenny,

The query is small but the plan is huge and likely to use a lot of
memory. What is with the rest of the system? Any paging? There are lots
of steps that are never executed in the plan. The plan looks great,
mostly unique index equality scans. Did you check pg_stat_activity for
wait_event_type and wait_event? What is your SQL waiting for?

Regards

--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com