On Tue, Nov 22, 2016 at 7:31 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> - 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.
Someone told me that there is something called an interested transaction list stored in the page header, and from that I infer that isn't *really* true. I think that unless you're interested in an affected row, rather than just some row that happens to be on the same page, you don't really have to worry about it. > 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. I imagine that temporal locality helps a lot. Most snapshots will be interested in the same row version. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers