On Wed, Dec 21, 2011 at 11:43 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> It seems like you've forgotten all of the previous discussion of how > we'd manage a page format version change. Maybe I've had too much caffeine. It's certainly late here. > Having two different page formats running around in the system at the > same time is far from free; in the worst case it means that every single > piece of code that touches pages has to know about and be prepared to > cope with both versions. That's a rather daunting prospect, from a > coding perspective and even more from a testing perspective. Maybe > the issues can be kept localized, but I've seen no analysis done of > what the impact would be or how we could minimize it. I do know that > we considered the idea and mostly rejected it a year or two back. I'm looking at that now. My feeling is it probably depends upon how different the formats are, so given we are discussing a 4 byte addition to the header, it might be doable. I'm investing some time on the required analysis. > A "utility to bump the page version" is equally a whole lot easier said > than done, given that the new version has more overhead space and thus > less payload space than the old. What does it do when the old page is > too full to be converted? "Move some data somewhere else" might be > workable for heap pages, but I'm less sanguine about rearranging indexes > like that. At the very least it would imply that the utility has full > knowledge about every index type in the system. I agree, rewriting every page is completely out and I never even considered it. >> I'm now personally game on to make something work here for 9.2. > > If we're going to freeze 9.2 in the spring, I think it's a bit late > for this sort of work to be just starting. I agree with that. If this goes adrift it will have to be killed for 9.2. -- Simon Riggs 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