On Fri, Nov 24, 2017 at 5:33 AM, Alexander Korotkov <a.korot...@postgrespro.ru> wrote: > pg_prune_xid makes sense only for heap pages. Once we introduce special > area for heap pages, we can move pg_prune_xid there and save some bytes in > index pages. However, this is an optimization not directly related to > 64-bit xids. Idea is that if we anyway change page format, why don't apply > this optimization as well? But if we have any doubts in this, it can be > removed with no problem.
My first reaction is that changing the page format seems like a non-starter, because it would break pg_upgrade. If we get the heap storage API working, then we could have a heap AM that works as it does today and a newheap AM with such changes, but I have a bit of a hard time imagining a patch that causes a hard compatibility break ever being accepted. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company