\d t: ERROR: XX000: cache lookup failed for relation

Resending to -hackers
https://www.postgresql.org/message-id/20180527022401.GA20949%40telsasoft.com

Is that considered an actionable problem?

Encountered consistently while trying to reproduce the vacuum full
pg_statistic/toast_2619 bug; while running a loop around VAC FULL and more in
another session:

[1]- Running { time sh -ec 'while :; do psql --port 5678 postgres -qc "VACUUM FULL pg_toast.pg_toast_2619"; psql --port 5678 postgres -qc "VACUUM FULL pg_statistic"; done'; date; } &
[2]+ Running time while :; do
psql postgres --port 5678 -c "INSERT INTO t SELECT i FROM generate_series(1,999999) i"; sleep 1; for a in `seq 999`;
do
psql postgres --port 5678 -c "ALTER TABLE t ALTER i TYPE int USING i::int"; sleep 1; psql postgres --port 5678 -c "ALTER TABLE t ALTER i TYPE bigint"; sleep 1;
done; psql postgres --port 5678 -c "TRUNCATE t"; sleep 1;
done &

$ psql --port 5678 postgres -x
psql (11beta1)
...
postgres=# \set VERBOSITY verbose
postgres=# \d t
ERROR: XX000: cache lookup failed for relation 8096742
LOCATION: flatten_reloptions, ruleutils.c:11065

Justin