Re: Automated way to find actual COMMIT LSN of subxact LSN

I find this to be unactionably vague.  What does it mean to claim "an
LSN is visible"?  An LSN might not even point to a WAL record, or it
might point to one that has nontransactional effects.  Moreover, any
behavior of this sort would destroy what I regard as a bedrock property
of recover-to-LSN, which is that there's a well defined, guaranteed-finite
stopping point.  (A property that recover-to-XID lacks, since the
specified XID might've crashed without recording either commit or abort.)

I think what you ought to be doing is digging the xmin out of the inserted
tuple you're concerned with and then doing recover-to-XID.  There's
definitely room for us to make it easier if the XID is a subxact rather
than a main xact.  But I think identifying the target XID is your job
not the job of the recovery-stop-point mechanism.