Re: reloption to prevent VACUUM from truncating empty pages at the end of relation

On Mon, Feb 25, 2019 at 7:01 PM Tsunakawa, Takayuki
<tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
>
> From: Michael Paquier [mailto:michael(at)paquier(dot)xyz]
> On Mon, Feb 25, 2019 at 03:59:21PM +0900, Masahiko Sawada wrote:
> > > Also, I think that this test may fail in case where concurrent
> > > transactions are running. So maybe should not run it in parallel to
> > > other tests.
> >
> > That's why autovacuum is disabled in this specific test, no? A comment
> > may be a good idea.
>
> Exactly. The table is disabled for autovacuum to avoid being influenced by autovacuum.
>

This test expects that the inserted tuple is always reclaimed by
subsequent vacuum, but it's not always true if there are concurrent
transactions. So size of the reloptions_test table will not be 0 if
the tuple is not vacuumed. In my environment this test sometimes
failed with 'make check -j 4'.

diff -U3 /home/masahiko/source/postgresql/src/test/regress/expected/reloptions.out
/home/masahiko/source/postgresql/src/test/regress/results/reloptions.out
--- /home/masahiko/source/postgresql/src/test/regress/expected/reloptions.out
2019-02-25 19:10:49.761438066 +0900
+++ /home/masahiko/source/postgresql/src/test/regress/results/reloptions.out
2019-02-25 19:12:34.885437911 +0900
@@ -117,7 +117,7 @@
SELECT pg_relation_size('reloptions_test');
pg_relation_size
------------------
- 0
+ 8192
(1 row)

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center