On Tue, Feb 6, 2018 at 4:35 AM, Kyotaro HORIGUCHI
<horiguchi.kyotaro@lab.ntt.co.jp> wrote:
>> It's starting to look like a timing effect indeed.
>
> It seems to be truncation skip, maybe caused by concurrent
> autovacuum.
Good point, I'll also disable autovacuum on vactst.
> See lazy_truncate_heap() for details. Updates of
> pg_stat_*_tables can be delayed so looking it also can fail. Even
> though I haven't looked the patch closer, the "SELECT
> pg_relation_size()" doesn't seem to give something meaningful
> anyway.
Maybe then "explain (analyze, buffers, costs off, timing off, summary
off) select * from vactst" then.
The point is to check that the relation's heap has 0 pages.