Justin,
Thanks for your continued interest.
I'm running PostgreSQL under AWS Aurora, and I didn't set it up or install it, so I'm not sure about the OS version.
I can't run the grep command since I don't know how to get down to the command line on the actual box running Aurora. I just connect to PostgreSQL from either my desktop or an EC2 Linux instance.
SQL I entered was:
set max_parallel_workers_per_gather = 0;
explain (analyze, buffers, settings)
select roys_creation_user, count(*)
from eu.royalty_with_null
group by roys_creation_user;
select roys_creation_user, count(*)
from eu.royalty_with_null
group by roys_creation_user;
The output is shown earlier in this thread.
I have no idea why I have IO timings but not buffers hit/read.
On Tue, Dec 21, 2021 at 1:13 PM Justin Pryzby <pryzby@xxxxxxxxxxxxx> wrote:
On Tue, Dec 21, 2021 at 12:33:06AM -0500, Tom Lane wrote:
> So now we have a real mystery about what is happening on Lars'
> system. Those numbers can't be right.
I realized Lars said it was x86_64/Linux, but I'm hoping to hear back with more
details:
What OS version?
Is it a VM of some type ?
How did you install postgres? From a package or compiled from source?
grep -r HAVE_CLOCK_GETTIME /usr/pgsql-13/include
Send the exact command and output you used to run the query?
Why does your explain output have IO timing but not Buffers: hit/read ?
--
Justin
