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From: Simon Windsor <[email protected]>
To: Laurenz Albe <[email protected]>
To: [email protected]
Subject: Re: Slow timestamp query after upgrading from Pg13 to Pg16
Date: Mon, 7 Apr 2025 20:25:28 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

Hi

We used pg_dump|pg_restore to migrate the data.

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

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

Simon

On 07/04/2025 15:51, Laurenz Albe wrote:
> On Mon, 2025-04-07 at 15:48 +0100, Simon Windsor wrote:
>> After upgrading a Db from Pg13 (Centos) to Pg16(Ubuntu) some queries
>> on a simple, large table (200M rows) are very slow
> If you used "pg_upgrade", did you ANALYZE the database?
>
> If that is not the problem, we can't guess what your problem might be
> unless you provide EXPLAIN (ANALYZE, BUFFERS, SETTINGS) output for auch a
> slow query.  Ideally, add the same information for the fast v13 case.
>
> Yours,
> Laurenz Albe

-- 
Simon Windsor

Eml: [email protected]
Mob: 0755 197 9733


“There is nothing in the world that some man cannot make a little worse and sell a little cheaper, and he who considers price only is that man's lawful prey.”

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