Re: BUG #17233: Incorrect behavior of DELETE command with bad subquery in WHERE clause

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, "lxndrkrlv(at)gmail(dot)com" <lxndrkrlv(at)gmail(dot)com>, "pgsql-bugs(at)lists(dot)postgresql(dot)org" <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #17233: Incorrect behavior of DELETE command with bad subquery in WHERE clause
Date: 2022-08-22 16:02:04
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On Sun, Aug 21, 2022 at 01:50:35PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > To improve things, it would be good if we could determine if LATERAL
> > will really fix the error, or at least detect one of the cases above we
> > have a clearer way to suggest a fix.
> Here's a proposed patch that tries to determine this by looking at
> ParseNamespaceItem flags. I'm not sure it's totally bulletproof,
> but it's likely good enough for a HINT.

Wow, this is great. I can see how people would be confused by the need
for LATERAL, and this is really a great boost for them.

> I felt that the conditional-expression nests in the existing ereport
> calls were nearly unintelligible already, so I rearranged the logic

Wow, I am glad you mentioned this. I never saw a ? b ? c : d : e used
before and I had to look it up, and I have been around C for a long time:

> to duplicate portions of the ereports instead. That could be debated
> perhaps. Also, as written some paths through errorMissingColumn
> will invoke the findNSItemForRTE search twice. I'm not too fussed
> about that: it's a pretty cheap search and anyway nobody should be
> bothering to shave microseconds off an error reporting path.


Bruce Momjian <bruce(at)momjian(dot)us>

Indecision is a decision. Inaction is an action. Mark Batterson

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