On 2013-12-23 14:15:29 -0500, Robert Haas wrote: > On Mon, Dec 23, 2013 at 1:57 PM, Andres Freund <and...@2ndquadrant.com> wrote: > > Well, all of the fundamental changes (combocids, the initial multixact > > introduction) have been quite some time ago. I think backward compat has > > a much higher value these days (I also don't see much point in looking > > at cmin/cmax for anything but diagnostic purposes). I don't think any of > > the usecases I've seen would be broken by either fk-locks (multixacts > > have been there before, doesn't matter much that they now contain > > updates) nor by forensic freezing. The latter because they really only > > checked that xmin/xmax were the same, and we hopefully haven't broken > > that... > > > > But part of my point really was the usability, not only the > > performance. Requiring LATERAL queries to be usable sensibly causes a > > "Meh" from my side ;) > > I simply can't imagine that we're going to want to add a system column > every time we change something, or even enough of them to cover all of > the things we've already got. We'd need at least infomask, infomask2, > and hoff, and maybe some functions for peeking through mxacts to find > the updater and locker XIDs and lock modes. With a couple of > functions we can do all that and not look back.
If system columns don't have an overhead anymore, I fail to see the advantage that functions have over simply accessing parts of the row in the normal way parts of rows are accessed. The only reasoning I can see is lessening the likelihood of conflicts - but that's essentially only solved via namespaced pg_ prefixes for functions as well. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
