On Mon, Sep 28, 2015 at 9:58 AM, Gavin Wahl <gavinw...@gmail.com> wrote: > It seems trivial to accelerate a MAX or MIN query with a BRIN index. You > just find the page range with the largest/smallest value, and then only scan > that one.
You might need to scan more than that if you don't find any rows that are visible. > Would that be hard to implement? I'm interested in working on it > if someone can give me some pointers. > > Somewhat harder but still possible would be using BRIN indexes to accelerate > ORDER BY. This would require a sorting algorithm that can take advantage of > mostly-sorted inputs. You would sort the page ranges by their minimum or > maximum value, then feed the sorting algorithm in that order. Currently you get a Bitmap Index Scan and Bitmap Heap Scan, and then a Sort node (quicksort or external sort). So the sort is already receiving data sorted in BRIN-block order, isn't it? Are you saying that the sort node should switch to something like insertion sort in this case? http://www.sorting-algorithms.com/nearly-sorted-initial-order -- Thomas Munro http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
