Robert Haas <robertmh...@gmail.com> writes: > [ Let's invent Oracle-style UNDO logs ]
I dunno. I remember being told years ago, by an ex-Oracle engineer, that he thought our approach was better. I don't recall all the details of the conversation but I think his key point was basically this: > - Reading a page that has been recently modified gets significantly > more expensive; it is necessary to read the associated UNDO entries > and do a bunch of calculation that is significantly more complex than > what is required today. Oracle spends a lot of time on this, and it's really cache-inefficient because the data is spread all over. This was what this guy felt in circa 2001; I'd have to think that the cache unfriendliness problem is much worse for modern hardware. Which is not to say that it's not worth experimenting with. But what you describe is going to be a huge amount of work even to get to the point where we could try to measure the actual costs and benefits :-( Heikki's been fooling with some ideas that I think have more promise. I wish he'd get to the point of presenting them publicly rather than just over beers at conferences. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers