Re: Consecutive Query Executions with Increasing Execution Time

Laurenz Albe <laurenz.albe@cybertec.at> 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