Re: pgsql: Avoid creation of the free space map for small heap relations, t

Amit Kapila <akapila(at)postgresql(dot)org> writes:
> Avoid creation of the free space map for small heap relations, take 2.

I think this patch still has some issues. Note the following two
recent buildfarm failures:

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=petalura&dt=2019-02-20%2004%3A20%3A01
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=dragonet&dt=2019-02-24%2022%3A48%3A02

Both of them failed in an assertion added by this patch:

TRAP: FailedAssertion("!((rel->rd_rel->relkind == 'r' || rel->rd_rel->relkind == 't') && fsm_local_map.map[oldPage] == 0x01)", File: "/home/bf/build/buildfarm-petalura/HEAD/pgsql.build/../pgsql/src/backend/storage/freespace/freespace.c", Line: 229)
...
2019-02-20 06:23:26.660 CET [5c6ce440.3bd2:4] LOG: server process (PID 17981) was terminated by signal 6: Aborted
2019-02-20 06:23:26.660 CET [5c6ce440.3bd2:5] DETAIL: Failed process was running: INSERT INTO T VALUES ( $1 )

I can even offer you a theory as to why we're managing to get through all
the core regression tests and then failing in ecpg: the failing test is
ecpg/test/thread/prep.pgc, and I think that may be the only place in our
tests where we stress concurrent insertions into a single small table.
So I think you've got race-condition issues here.

It might or might not be significant that these two animals are part
of Andres' JIT-enabled menagerie. I could see that affecting test
timing to the point of showing a symptom that's otherwise hard to hit.

regards, tom lane