Re: ERROR: too late to create a new PlaceHolderInfo

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Richard Guo <guofenglinux(at)gmail(dot)com>
Cc: Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: ERROR: too late to create a new PlaceHolderInfo
Date: 2026-09-17 15:41:07
Message-ID: 644229.1789659667@sss.pgh.pa.us
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I wrote:
> I agree with that sounding more principled, but I wonder if we should
> think bigger than just tweaking add_nullingrels_if_needed: if we're
> desirous of de-duplicating PHVs, why not do that across the board,
> for every place that makes PHVs? So we'd mechanize this in
> make_placeholder_expr's assignment of phid rather than somewhere else.

Actually, we can't be too gung-ho about that: we should not merge
PHVs if their expressions are volatile. It's not quite clear to me
whether that's a problem for the join-alias-Vars case.

regards, tom lane

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