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 "Thu, 11 Apr 2024 15:41:42 +0800"
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Date: Thu, 11 Apr 2024 10:13:15 -0400
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Richard Guo <guofenglinux@gmail.com> writes:
> On Wed, Apr 10, 2024 at 10:16 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> 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.

> Do you think we can have a parameter in the new get_expr_result_rtfunc()
> function to indicate whether we want to build an intermediate tupdesc
> when we have a coldeflist?  Then we can set it to true in the two places
> that are correct already, and set it to false at the places we need to
> fix.  But I'm not sure if including such a new parameter would be an
> improvement or just make it worse.

I did think about that, but it seems mighty weird.  The semantics of
the flag would have to be something like "I want a tupdesc when the
result type is COMPOSITE, but not when it's RECORD", which seems
rather arbitrary.

Perhaps it'd be sufficient to add a note to the header comment of
get_expr_result_type warning about when not to use it.

			regards, tom lane