There is still one significant difference of my prototype implementation with SQL standard: it associates timestamp with select statement, not with particular table. It seems to be more difficult to support and I am not sure that joining tables from different timelines has much sense. But certainly it also can be fixed.
I think the main use I would find for this feature is something like:
select * from foo except select * from foo as old_foo as of '<some time>';
So I would be grateful if you can make that work. Also, I think conforming to the standards is pretty important where it is feasible to do that.
