Feedback-ID: ia2694551:Fastmail
Date: Sun, 18 May 2025 08:23:06 -0400
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Junwang Zhao <zhjwpku@gmail.com>, Andrei Lepikhov <lepihov@gmail.com>,
	"pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>,
 Tomas Vondra <tomas@vondra.me>, Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Incorrect calculation of path fraction value in MergeAppend
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On 2025-May-18, Alexander Korotkov wrote:

> I've slightly revised the patch: commit message and one comment.  I
> think this is clearly a bugfix, and it should be backpatched.  I'm
> going to push and backpatch it if no objections.

I think we mostly avoid backpatching changes that can cause significant
planning changes, because the consequences for existing systems could be
catastrophic -- even if the known plan changes are beneficial.  IMO you
need to spend a lot more effort in showing that this can't possibly harm
anything, before backpatching.

Personally I can see getting this in 18beta2 without too much additional
arguing for it.  But for 15-17 you'd need a lot more support than is
evident in this thread.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/