Re: Proposal: Snapshot cloning

"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> You got me. My description was too loose, but you also got the rough
> picture. We'll save the detail for another day, but we all know its a
> bridge we will have to cross one day, soon. I wasn't meaning to raise
> this specific discussion now, just to say that publishing snapshots for
> known LRTs is one way by which we can solve the LRT/VACUUMing issue.

I don't actually see that it buys you a darn thing ... you still won't
be able to delete dead updated tuples because of the possibility of the
LRT deciding to chase ctid chains up from the tuples it can see. You
also seem to be assuming that a transaction can have only one snapshot,
which is not something we can enforce in enough cases to make it a very
useful restriction.

regards, tom lane