On Mon, Mar 8, 2021 at 7:34 PM Peter Geoghegan <p...@bowt.ie> wrote: > > One possible > > consequence that I'm concerned about is sequential scan performance. > > For an index scan, you just jump to the line pointer you want and then > > go get the tuple, but a sequential scan has to loop over all the line > > pointers on the page, and skipping a lot of dead ones can't be > > completely free. A small increase in MaxHeapTuplesPerPage probably > > wouldn't matter, but the proposed increase of almost 10x (291 -> 2042) > > is a bit scary. > > I agree. Maybe the real problem here is that MaxHeapTuplesPerPage is a > generic constant. Perhaps it should be something that can vary by > table, according to practical table-level considerations such as > projected tuple width given the "shape" of tuples for that table, etc.
Speaking of line pointer bloat (and "irreversible" bloat), I came across something relevant today. I believe that this recent patch from Matthias van de Meent is a relatively easy way to improve the situation: https://www.postgresql.org/message-id/flat/CAEze2WjgaQc55Y5f5CQd3L%3DeS5CZcff2Obxp%3DO6pto8-f0hC4w%40mail.gmail.com -- Peter Geoghegan
