Re: pgsql: Support partition pruning at execution time

On 8 April 2018 at 12:15, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> Yeah, I don't quite understand this problem, and I tend to agree that
> it likely isn't this patch's fault. However, for the moment I'm going
> to avoid pushing the patch you propose because maybe there's a bug
> elsewhere and it'd be good to understand it. I'm looking at it now.
>
> If others would prefer me to push David's patch (or do so themselves),
> I'm not dead set against that.

I just wanted to share this:

#!/bin/bash
for i in {1..1000000}
do
if [ $(psql --no-psqlrc -w -v ON_ERROR_STOP=0 -d postgres -q
-A -F " " -t <<EOF
drop table if exists tprt;
create table tprt (col1 int);
create index tprt_idx on tprt (col1);
insert into tprt values (10), (20), (501),
(502), (505), (1001), (4500);
vacuum tprt;
select relallvisible from pg_Class where
relname like 'tprt%' and relkind = 'r';
EOF
) = "0" ];
then
echo "[$(date --iso-8601=seconds)]: 0"
fi

done

If I run this I only get the wrong result from the visibility map in
60 second intervals:

Check this output:

[2018-04-08T02:50:34+0000]: 0
[2018-04-08T02:50:34+0000]: 0
[2018-04-08T02:50:34+0000]: 0
[2018-04-08T02:50:34+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:50:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:51:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0
[2018-04-08T02:52:35+0000]: 0

It happens 12 or 13 times on my machine, then does not happen again
for 60 seconds, then happens again.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services