On Sun, 12 May 2002, Tom Lane wrote:
> Manfred Koizar <mkoi-pg@aon.at> writes:
> > A *stack* of _active_ transaction numbers is not sufficient, we need
> > the whole *tree* of _all_ transactions belonging to the current top
> > level transaction. This is, want I wanted to model in my pg_subtrans
> > "table". And pg_subtrans cannot be a private structure, because it
> > has to be inspected by other transactions too (cf. example above).
>
> Hmm. This seems to me to be vastly overdesigning the feature. I've
> never yet seen a practical application for more than one level of
> subtransaction, so I question whether we should buy into a substantially
> more complex implementation to support the more general case.
I think it'd depend on how pervasive the feature is going to be. If we
allow functions/rules/etc to start subtransactions I'm not sure it'd
be safe to say that only one level is safe since you might not know that
your subtransaction calls something that wants to start a subtransaction,
but you'd probably expect that anything it does would be undone when you
rollback your subtransaction, just like it would if the items weren't
in a subtransaction.