Date: Mon, 10 Nov 2025 15:19:23 -0600
From: Nathan Bossart <nathandbossart@gmail.com>
To: Corey Huinker <corey.huinker@gmail.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: vacuumdb: add --dry-run
Message-ID: <aRJW2_Yy9ALMkZUa@nathan>
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On Mon, Nov 10, 2025 at 02:44:41PM -0500, Corey Huinker wrote:
> This is a small patch to add a new option to vacuumdb to answer the
> question "what commands will actually be run by this combination of
> command-line switches against this database?" without actually running the
> commands.

My attempts to test this all got stuck in wait_on_slots().  I haven't
looked too closely, but I suspect the issue is that the socket never
becomes readable because we don't send a query.  If I set free_slot->inUse
to false before printing the command, it no longer hangs.  We probably want
to create a function in parallel_slot.c to mark slots that we don't intend
to give a query as idle.

-- 
nathan