From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Zhang Mingli <zmlpostgres(at)gmail(dot)com>, Surafel Temesgen <surafel3000(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: useless LIMIT_OPTION_DEFAULT
Date: 2023-12-16 16:42:28
Message-ID: 202312161642.dzsvloromlfl@alvherre.pgsql
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On 2023-Dec-14, Tom Lane wrote:

> Zhang Mingli <zmlpostgres(at)gmail(dot)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.


Álvaro Herrera Breisgau, Deutschland —
"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)

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