Re: remove_useless_joins vs. bug #19560

From: Richard Guo <guofenglinux(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Thom Brown <thom(at)linux(dot)com>, Jacob Brazeal <jacob(dot)brazeal(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: remove_useless_joins vs. bug #19560
Date: 2026-09-17 07:15:15
Message-ID: CAMbWs49LS9AMn-MV2Zm7xZ6kjZJMa4gVuH_h83nF=7U+0m322Q@mail.gmail.com
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On Thu, Sep 17, 2026 at 11:52 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> The main consumer of varnosyn is ruleutils.c, so I don't like
> the fact that this test case isn't showing what ruleutils will
> do with the Var. If we make it be "explain verbose", do we
> get a display of the problematic Var?

The Var is displayed, but not via varnosyn. ruleutils.c uses varnosyn
only when dpns->plan is NULL, and EXPLAIN always sets the plan before
deparsing an expression, so it prints the semantic referent (a.b_id).

But I think it'd still be better to use "explain verbose", so at least
what ruleutils prints is recorded. I'll make that change before push.

- Richard

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