Feedback-ID: ia2694551:Fastmail
Date: Sat, 16 Dec 2023 17:42:28 +0100
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Zhang Mingli <zmlpostgres@gmail.com>, 
	Surafel Temesgen <surafel3000@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: useless LIMIT_OPTION_DEFAULT
Message-ID: <202312161642.dzsvloromlfl@alvherre.pgsql>
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On 2023-Dec-14, Tom Lane wrote:

> Zhang Mingli <zmlpostgres@gmail.com> writes:
> > By reading the codes, I found that we process limit option as LIMIT_OPTION_WITH_TIES when using WITH TIES
> > and all others are LIMIT_OPTION_COUNT by  commit 357889eb17bb9c9336c4f324ceb1651da616fe57.
> > And check actual limit node in limit_needed().
> > There is no need to maintain a useless default limit enum.
> 
> I agree, that looks pretty useless.  Our normal convention for
> representing not having any LIMIT clause would be to not create
> a SelectLimit node at all.  I don't see why allowing a second
> representation is a good idea, especially when the code is not
> in fact doing that.
> 
> git blame shows that this came in with 357889eb1.  Alvaro,
> Surafel, do you want to argue for keeping things as-is?

I looked at the history of this.  That enum member first appeared as a
result of your review at [1], and the accompanying code at that time did
use it a few times.  The problem is that I later ([2]) proposed to rewrite
that code and remove most of the uses of that enum member, but failed to
remove it completely.

So, I think we're OK to remove it.  I'm going to push Zhang's patch
soon unless there are objections.

[1] https://postgr.es/m/3277.1567722389@sss.pgh.pa.us
[2] https://postgr.es/m/20191125203442.GA30191@alvherre.pgsql

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"Doing what he did amounts to sticking his fingers under the hood of the
implementation; if he gets his fingers burnt, it's his problem."  (Tom Lane)