From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Amit Langote <amitlangote09@gmail.com>,
        Alvaro Herrera <alvherre@alvh.no-ip.org>,
        Andres Freund <andres@anarazel.de>,
        Daniel Gustafsson <daniel@yesql.se>,
        David Rowley <dgrowleyml@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@postgresql.org>,
        Thom Brown <thom@linux.com>
Subject: Re: generic plans and "initial" pruning
In-reply-to: <CA+TgmoaLXb+JpPGYrw08BNQM74VEMPH_MOy5SK4p_+TDXH2z9w@mail.gmail.com>
References: <CA+HiwqFpZ80UJKr4tZus4Omgg7YESzFXKSwSHRW2Ap2=XSVyUA@mail.gmail.com> <202406191709.jbvpf7d7hl6g@alvherre.pgsql> <CA+HiwqF+3tv=tuB9EVfOj9YcXhSq477X+1RKOpJ5JqCCj3qgww@mail.gmail.com> <CA+TgmobHL_vTjOdy6KVMVeW-CQQmXXz_yU6Q9d2YjnVfFxuy6A@mail.gmail.com> <CA+HiwqHL=aGU9Y4RYXQ5VCp4L5NVdiaQLLoXN3NCQQQMKo0ByQ@mail.gmail.com> <CA+TgmoabYD=pnccFLzbbREFsqkFgE4EZ+FdHoTOhgCqn4jP2Cw@mail.gmail.com> <CA+HiwqE_rQ9pZnkXeoHdds2kgAiT7XNNHZW8gTGicBdXv0rwnw@mail.gmail.com> <CA+TgmoY2drv9PmrRAC7AR77mkx09sOh-+5qJkHB_hLKeHRNqzQ@mail.gmail.com> <1386845.1724086454@sss.pgh.pa.us> <CA+TgmoaLXb+JpPGYrw08BNQM74VEMPH_MOy5SK4p_+TDXH2z9w@mail.gmail.com>
Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Mon, 19 Aug 2024 13:38:28 -0400"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1393409.1724089927.1@sss.pgh.pa.us>
Date: Mon, 19 Aug 2024 13:52:07 -0400
Message-ID: <1393410.1724089927@sss.pgh.pa.us>
Archived-At: <https://www.postgresql.org/message-id/1393410.1724089927%40sss.pgh.pa.us>
Precedence: bulk

Robert Haas <robertmhaas@gmail.com> writes:
> But that seems somewhat incidental to what this thread is about.

Perhaps.  But if we're running into issues related to that, it might
be good to set aside the long-term goal for a bit and come up with
a cleaner answer for intra-session locking.  That could allow the
pruning problem to be solved more cleanly in turn, and it'd be
an improvement even if not.

> Do you have a view on what the way forward might be?

I'm fresh out of ideas at the moment, other than having a hope that
divide-and-conquer (ie, solving subproblems first) might pay off.

> This thread has gotten a tad depressing, honestly. All of the opinions
> about what we ought to do seem to be based on the firm conviction that
> X or Y or Z will not work, rather than on the confidence that A or B
> or C will work. Yet I'm inclined to believe this problem is solvable.

Yeah.  We are working in an extremely not-green field here, which
means it's a lot easier to see pre-existing reasons why X will not
work than to have confidence that it will work.  But hey, if this
were easy then we'd have done it already.

			regards, tom lane