Re: Prevent writes on large objects in read-only transactions

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, Jun 1, 2022 at 1:29 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>> Now the LO handling is quite old, and I am not sure if this is worth
>> changing as we have seen no actual complains about that with read-only
>> transactions, even if I agree on that it is inconsistent. That could
>> cause more harm than the consistency benefit is worth :/

> The message that started this thread is literally a complaint about
> that exact thing.

Yeah. I think this is more nearly "nobody had noticed" than "everybody
thinks this is okay".

> We seem to do this fairly often on this list, honestly. Someone posts
> a message saying "X is broken" and someone agrees and says it's a good
> idea to fix it and then a third person responds and says "let's not
> change it, no one has ever {noticed that,cared before,complained about
> it}".

It's always appropriate to consider backwards compatibility, and we
frequently don't back-patch a change because of worries about that.
However, if someone complains because we start rejecting this as of
v15 or v16, I don't think they have good grounds for that. It's just
obviously wrong ... unless someone can come up with a plausible
definition of read-only-ness that excludes large objects. I don't
say that that's impossible, but it sure seems like it'd be contorted
reasoning. They're definitely inside-the-database entities.

regards, tom lane