Any reason to keep HEAP_HASOID_OLD?

Hi,

On 2026-04-28 16:27:59 +1200, David Rowley wrote:

Andres mentioned to me that I might want to look at
HeapTupleHeaderGetOidOld() as there's a comment and some code there
that would lead you to believe we can still have tuples with oids. If
that were true, the code I recently added for getting 'tp' in
slot_selectively_deform_heap_tuple() is wrong.

#define HEAP_HASOID_OLD 0x0008 /* has an object-id field */

On 11.22, I tried:

create extension pageinspect;
create table t1 (a int) with oids;
insert into t1 select generate_Series(1,1000);
select count(*) from heap_page_items(get_raw_page('public.t1',0))
where t_infomask & 8 <> 0;

count
-------
185

alter table t1 set without oids;

select count(*) from heap_page_items(get_raw_page('public.t1',0))
where t_infomask & 8 <> 0;
count
-------
0

Yea, it seems we've started rewriting tables for SET WITHOUT OIDS a long time
ago:
/*
* If we dropped the OID column, must adjust pg_class.relhasoids and tell
* Phase 3 to physically get rid of the column. We formerly left the
* column in place physically, but this caused subtle problems. See
* http://archives.postgresql.org/pgsql-hackers/2009-02/msg00363.php
*/
if (attnum == ObjectIdAttributeNumber)

I also verified that we don't allow SET WITHOUT OIDS when it's used as a row
type in another table.

And also, if I try to pg_upgrade before SET WITHOUT OIDS, I get:

$ pg_upgrade -d pgdata11 -D pgdata -b ~/pg11/bin -B ~/pg/bin
Performing Consistency Checks
-----------------------------
Checking cluster versions ok
Checking database user is the install user ok
Checking database connection settings ok
Checking for prepared transactions ok
Checking for system-defined composite types in user tables ok
Checking for reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for user-defined encoding conversions ok
Checking for user-defined postfix operators ok
Checking for incompatible polymorphic functions ok
Checking for tables WITH OIDS fatal

So, I'm not following how we could get a tuple with OIDs in versions after 11.

I don't see it either. Wonder why I / decided to leave it :/.

Should we get rid of HEAP_HASOID_OLD and the code that relates to it?

Looks like it.

Greetings,

Andres Freund