From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
cc: Robert Haas <robertmhaas@gmail.com>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Remove configure --disable-float4-byval and
 --disable-float8-byval
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Comments: In-reply-to Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
	message dated "Sat, 02 Nov 2019 08:46:12 +0100"
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Date: Sat, 02 Nov 2019 11:26:59 -0400
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Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> On 2019-11-01 15:41, Robert Haas wrote:
>> On a related note, why do we store typbyval in the catalog anyway
>> instead of inferring it from typlen and maybe typalign? It seems like
>> a bad idea to record on disk the way we pass around values in memory,
>> because it means that a change to how values are passed around in
>> memory has ramifications for on-disk compatibility.

> This sounds interesting.  It would remove a pg_upgrade hazard (in the 
> long run).

> There is some backward compatibility to be concerned about.

Yeah.  The point here is that typbyval specifies what the C functions
concerned with the datatype are expecting.  We can't just up and say
"we're going to decide that for you".

I do get the point that supporting two different typbyval options
for float8 and related types is a nontrivial cost.

			regards, tom lane