Feedback-ID: i76984098:Fastmail
Message-ID: <9653cc7d-3275-4255-ba4d-fba3778f67e6@aklaver.com>
Date: Mon, 7 Apr 2025 12:36:32 -0700
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: Slow timestamp query after upgrading from Pg13 to Pg16
To: Simon Windsor <simon.windsor@cornfield.me.uk>,
 Laurenz Albe <laurenz.albe@cybertec.at>, pgsql-general@postgresql.org
References: <27b2975b-c078-45cf-815d-eddbedbda153@cornfield.me.uk>
 <092224fb0376bbc6a5f777199dde3cb9cd1ebf99.camel@cybertec.at>
 <692a315e-6dd8-4194-8c7f-c45425852e77@cornfield.me.uk>
Content-Language: en-US
From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <692a315e-6dd8-4194-8c7f-c45425852e77@cornfield.me.uk>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Archived-At: <https://www.postgresql.org/message-id/9653cc7d-3275-4255-ba4d-fba3778f67e6%40aklaver.com>
Precedence: bulk

On 4/7/25 12:25, Simon Windsor wrote:
> Hi
> 
> We used pg_dump|pg_restore to migrate the data.

Did you do an ANALYZE on the Postgres 16 instance after the pg_restore?

> 
> The full explain plan is at https://explain.depesz.com/s/742M. The SQL
> 
> explain (analyze, buffers) select count(*) from consignments where 
> (req_status_tstamp >= '2025-03-28 00:00'::timestamp and 
> req_status_tstamp <= '2025-03-28 01:00'::timestamp);
> 
> takes 2-3s with the old Pg13 DB, and over a minute with Pg16

Do you have an EXPLAIN ANALYZE for the Postgres 13 case?

> 
> After spending many hours looking at DB settings and Statistic settings 
> I am at a loss/
> 
> Simon
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com