Laurenz Albe <laurenz.albe@xxxxxxxxxxx> writes: > On Tue, 2019-12-17 at 11:11 -0500, Jeff Janes wrote: >> 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. Nonetheless, the presented test case consists of repeatedly doing the same query, in a fresh session each time. If there's not other activity then this should reach some sort of steady state. The table is apparently fairly large, so I don't find it surprising that the steady state fails to be 100% cached. regards, tom lane
