Re: StandbyRecoverPreparedTransactions recovers subtrans links incorrectly

Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> I can't see any reason now why overwriteOK should exist at all. I'm
> guessing that the whole "overwriteOK" idea was an incorrect response
> to xids appearing where they shouldn't have done because of the
> mistake you just corrected. So I will now remove the parameter from
> the call.

Seems reasonable, but I don't like the logic change you made in
SubTransSetParent; you broke the former invariant, for non-Assert
builds, that the target pg_subtrans entry is guaranteed to have
the correct value on exit. I do like fixing it to not dirty the
page unnecessarily, but I'd suggest that we write it like

if (*ptr != parent)
{
Assert(*ptr == InvalidTransactionId);
*ptr = parent;
SubTransCtl->shared->page_dirty[slotno] = true;
}

regards, tom lane