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From: jian he <jian.universality@gmail.com>
Date: Sat, 20 Dec 2025 21:14:46 +0800
Message-ID: 
 <CACJufxFV5KqmF86upFmX2tPzfKMWjWNf8+uYiYufLKatOsYXQw@mail.gmail.com>
Subject: Re: SQL-level pg_datum_image_equal
To: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Thu, Dec 11, 2025 at 1:46=E2=80=AFAM Matthias van de Meent
<boekewurm+postgres@gmail.com> wrote:
>
> Hi,
>

>

> So, attached is a simple and to-the-point patch that adds the function
> mentioned in $subject, which will tell the user whether two values of
> the same type have an exactly equal binary representation, using
> datum_image_eq.
>

hi.

maybe Table 9.76
(https://www.postgresql.org/docs/current/functions-info.html#FUNCTIONS-INFO=
-CATALOG)
is the right place for this function.

corner case confused me, I think this is related to null handling,
maybe not related to this.
create type t1 as (a int, b text);
select pg_datum_image_equal('(,)'::t1, $$(,)$$::t1);
select pg_datum_image_equal('(,)'::t1, NULL::t1);
select '(,)'::t1 is null, NULL::t1 is null;

enforce_generic_type_consistency already resolved generic type.
see
select pg_datum_image_equal('1','1');
ERROR:  could not determine polymorphic type because input has type unknown

so
+ if (!OidIsValid(typ))
+ {
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("could not determine type")));
+ }
this part should be elog(ERROR.....) ?


--
jian
https://www.enterprisedb.com/