Thread

Re: SQL-level pg_datum_image_equal

jian he <jian.universality@gmail.com> — 2025-12-20T13:14:46Z

On Thu, Dec 11, 2025 at 1:46 AM 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/