Re: dsa_allocate() faliure

On Thu, Feb 7, 2019 at 9:10 PM Jakub Glapa <jakub.glapa@gmail.com> wrote:
> > Do you have query logging enabled ?  If not, could you consider it on at least
> one of those servers ?  I'm interested to know what ELSE is running at the time
> that query failed.
>
> Ok, I have configured that and will enable in the time window when the errors usually occur. I'll report as soon as I have something.

I don't have the answer yet but I have some progress: I finally
reproduced the "could not find %d free pages" error by running lots of
concurrent parallel queries.  Will investigate.

Set up:

create table foo (p int, a int, b int) partition by list (p);
create table foo_1 partition of foo for values in (1);
create table foo_2 partition of foo for values in (2);
create table foo_3 partition of foo for values in (3);
alter table foo_1 set (parallel_workers = 4);
alter table foo_2 set (parallel_workers = 4);
alter table foo_3 set (parallel_workers = 4);
insert into foo
select generate_series(1, 10000000)::int % 3 + 1,
       generate_series(1, 10000000)::int % 50,
       generate_series(1, 10000000)::int % 50;
create index on foo_1(a);
create index on foo_2(a);
create index on foo_3(a);
create index on foo_1(b);
create index on foo_2(b);
create index on foo_3(b);
analyze;

Then I ran three copies of :

#!/bin/sh
(
  echo "set max_parallel_workers_per_gather = 4;"
  for I in `seq 1 100000`; do
    echo "explain analyze select count(*) from foo where a between 5
and 6 or b between 5 and 6;"
  done
) | psql postgres

-- 
Thomas Munro
http://www.enterprisedb.com