From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Laurenz Albe <laurenz.albe@cybertec.at>, suchithjn22@gmail.com,
        pgsql-docs@lists.postgresql.org
Subject: Re: The documentation for storage type 'plain' actually allows single
 byte header
In-reply-to: <20230115231950.hvlzxho6pccmrn6g@awork3.anarazel.de>
References: 
 <167336599095.2667301.15497893107226841625@wrigleys.postgresql.org>
 <d99b3e0beebdde0741d28035aaea7f4af56fa050.camel@cybertec.at>
 <1698750.1673818827@sss.pgh.pa.us>
 <20230115230320.d3mtlzek6dv7mgxx@awork3.anarazel.de>
 <1747092.1673824101@sss.pgh.pa.us>
 <20230115231950.hvlzxho6pccmrn6g@awork3.anarazel.de>
Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Sun, 15 Jan 2023 15:19:50 -0800"
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Date: Sun, 15 Jan 2023 18:41:22 -0500
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Andres Freund <andres@anarazel.de> writes:
> On 2023-01-15 18:08:21 -0500, Tom Lane wrote:
>> ri_newTupleSlot has the tupdesc we want, planSlot is a virtual slot
>> that has the bogus tupdesc, and for some reason heap_form_tuple is
>> getting called with planSlot's tupdesc not ri_newTupleSlot's.

> The way we copy a slot into a heap slot is to materialize the source slo=
t and
> copy the heap tuple into target slot. Which is also what happened before=
 the
> slot type abstraction (hence the problem also existing before that was
> introduced).

Hmm.  For the case of virtual->physical slot, that doesn't sound
terribly efficient.

> I think it's fairly fundamental that copying between two slots assumes a
> compatible tupdescs.

We could possibly make some effort to inject the desired attstorage
properties into the planSlot's tupdesc.  Not sure where would be a
good place.

			regards, tom lane