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From: Laurenz Albe <[email protected]>
To: Murthy Nunna <[email protected]>
To: [email protected] <[email protected]>
Subject: Re: Query Spins
Date: Mon, 01 Sep 2025 09:52:26 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <DM8PR09MB6677D376F84879E730AAB223B807A@DM8PR09MB6677.namprd09.prod.outlook.com>
References: <DM8PR09MB6677D376F84879E730AAB223B807A@DM8PR09MB6677.namprd09.prod.outlook.com>

On Mon, 2025-09-01 at 03:52 +0000, Murthy Nunna wrote:
> Pg16.10
>  
> I have a query which runs fine most of the time. When it runs fine, it spawns
> parallel workers. In pg_stat_activity, wait_event is blank, state is active and
> backend_type = "client backend" for the main query. For parallel workers of
> this query I see wait_event = MessageQueueSend, state is active and
> backend_type = "parallel worker"
>  
> But some times, it has no parallel workers. wait_event is blank, state is active
> and backend_type =client backend. And it never ends. It takes up lot of CPU.
> The socket on both server and client server are in ESTABLISHED state
> (netstat -tulpa | grep <client_port>).

Perhaps no workers are spawned because "max_parallel_workers" has already
been exhausted by other backends.  Check for the number of concurrent parallel
workers next time you get the error.

I cannot know the source of your performance problems, but perhaps it is
a combination of system overload and lack of available parallel worker
processes, which might well go together.

Yours,
Laurenz Albe

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