Re: Are these metadata ALTER TABLE commands transactionally safe?

On Thursday, May 14, 2026, Ron Johnson <ronljohnsonjr(at)gmail(dot)com> wrote:

> On Thu, May 14, 2026 at 5:26 PM David G. Johnston <
> david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
>> On Thursday, May 14, 2026, Ron Johnson <ronljohnsonjr(at)gmail(dot)com> wrote:
>>
>>> PG 17.9
>>>
>>> BEGIN;
>>> ALTER TABLE x RENAME TO x_hold;
>>> ALTER TABLE y.x SET SCHEMA a;
>>> ALTER TABLE x OWNER TO foo;
>>> COMMIT;
>>>
>>>
>> Define “transactionally safe”.
>>
>
> Any open transactions will still see the original tables.
>
>

That would involve locking, most DDL simply won’t happen while open
transactions are using the objects. Normal visibility semantics then apply
beyond that - which depend on isolation level.

David J.