On Tue, Mar 21, 2017 at 01:14:00PM -0400, Robert Haas wrote: > On Tue, Mar 21, 2017 at 1:08 PM, Peter Geoghegan <p...@bowt.ie> wrote: > > On Tue, Mar 21, 2017 at 10:04 AM, Robert Haas <robertmh...@gmail.com> wrote: > >> I think that's a good question. I previously expressed similar > >> concerns. On the one hand, it's hard to ignore the fact that, in the > >> cases where this wins, it already buys us a lot of performance > >> improvement. On the other hand, as you say (and as I said), it eats > >> up a lot of bits, and that limits what we can do in the future. On > >> the one hand, there is a saying that a bird in the hand is worth two > >> in the bush. On the other hand, there is also a saying that one > >> should not paint oneself into the corner. > > > > Are we really saying that there can be no incompatible change to the > > on-disk representation for the rest of eternity? I can see why that's > > something to avoid indefinitely, but I wouldn't like to rule it out. > > Well, I don't want to rule it out either, but if we do a release to > which you can't pg_upgrade, it's going to be really painful for a lot > of users. Many users can't realistically upgrade using pg_dump, ever. > So they'll be stuck on the release before the one that breaks > compatibility for a very long time.
Right. If we weren't setting tuple and tid bits we could imrpove it easily in PG 11, but if we use them for a single-change WARM chain for PG 10, we might need bits that are not available to improve it later. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription + -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers