On Wed, Sep 7, 2016 at 1:45 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > On 6 September 2016 at 19:59, Tom Lane <t...@sss.pgh.pa.us> wrote: > >> The idea of looking to the stats to *guess* about how many tuples are >> removable doesn't seem bad at all. But imagining that that's going to be >> exact is folly of the first magnitude. > > Yes. Bear in mind I had already referred to allowing +10% to be safe, > so I think we agree that a reasonably accurate, yet imprecise > calculation is possible in most cases.
That would all be well and good if it weren't trivial to do what Robert suggested. This is just a large unsorted list that we need to iterate throught. Just allocate chunks of a few megabytes and when it's full allocate a new chunk and keep going. There's no need to get tricky with estimates and resizing and whatever. -- greg -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers