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From: Andrey Borodin <[email protected]>
To: Roman Khapov <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Cancel problems of query to pg_stat_statements
Date: Mon, 28 Apr 2025 11:16:19 +0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>



> On 24 Apr 2025, at 22:49, Roman Khapov <[email protected]> wrote:
> 
> Hi!
>  Recently we faced a problem in out production psql installation, which was that we had to cancel all requests to the db, including performance monitoring requests, that uses ps_stat_statements. But we could not cancel the request in usual way, and had to kill -9 the pg process of it.

Interesting problem, thanks for raising it!

>  We've noticed that the the query execution stuck on PGSS_TEXT_FILE file reading in function qtext_load_file, which doesn't have CHECK_FOR_INTERRUPTS in the read cycle. In addition to our case with large PGSS_TEXT_FILE (and maybe the problems with virtual disk i/o) that can explain uncancellable pg_stat_statements queries.

I'm afraid it might be not so easy to add CHECK_FOR_INTERRUPTS there. Most probably you was holding a LWLockAcquire(pgss->lock, LW_SHARED) somewhere (do you have a backtrace?), which prevent interrupts anyway.

Thanks!


Best regards, Andrey Borodin.

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