On Tue, 2019-12-17 at 11:11 -0500, Jeff Janes wrote: > On Tue, Dec 17, 2019 at 8:08 AM Laurenz Albe <laurenz.albe@xxxxxxxxxxx> wrote: > > On Mon, 2019-12-16 at 15:50 -0500, Tom Lane wrote: > > > Peter Geoghegan <pg@xxxxxxx> writes: > > > > Why do the first and the twentieth executions of the query have almost > > > > identical "buffers shared/read" numbers? That seems odd. > > > > > > It's repeat execution of the same query, so that doesn't seem odd to me. > > > > Really? Shouldn't the blocks be in shared buffers after a couple > > of executions? > > If it is doing a seq scan (I don't know if it is) they intentionally use a > small ring buffer to, so they evict their own recently used blocks, rather > than evicting other people's blocks. So these blocks won't build up in > shared_buffers very rapidly just on the basis of repeated seq scans. Sure, but according to the execution plans it is doing a Parallel Index Only Scan. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
