From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
cc: Tender Wang <tndrwang@gmail.com>, exclusion@gmail.com,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18422: Assert in expandTupleDesc() fails on row mismatch
 with additional SRF
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Comments: In-reply-to Richard Guo <guofenglinux@gmail.com>
	message dated "Wed, 10 Apr 2024 15:58:51 +0800"
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Date: Wed, 10 Apr 2024 10:16:41 -0400
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Richard Guo <guofenglinux@gmail.com> writes:
> On Wed, Apr 10, 2024 at 11:32 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I guess we could.  It won't matter because the following code will
>> reject RECORD in any case; but we could save a few cycles by not
>> calling get_expr_result_tupdesc there.

> Indeed.  I think it would be better to add this same rule to
> process_function_rte_ref(), or at least write some comments there to
> explain why it is not necessary to check rtfunc->funccolnames while
> other places do.

Wilco.  Another thing I was considering, but didn't pull the trigger
on in the draft patch, was to introduce a funcapi.c function on the
order of
	get_expr_result_rtfunc(RangeTblFunction *rtfunc, ...)
which would encapsulate applying either BuildDescFromLists or
get_expr_result_type.  I didn't do it because I found that the
only places that would want to use it are the two that are correct
already; the places we still need to fix have short-cuts they can
take rather than building an intermediate tupdesc.  (The present
bug could be summarized as "the short-cuts still need to pay
attention to the coldeflist".)  But the advantage of doing this
anyway is that its header comment would be a natural place to
document this issue and policy.  Thoughts?

			regards, tom lane