Every once in awhile we get failures like this one: https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=gull&dt=2019-11-05%2008%3A27%3A27
diff -U3 /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/../pgsql/src/test/regress/expected/vacuum.out /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/src/test/regress/results/vacuum.out --- /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/../pgsql/src/test/regress/expected/vacuum.out 2019-08-11 03:02:18.921535948 -0700 +++ /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/src/test/regress/results/vacuum.out 2019-11-05 00:50:42.381244885 -0800 @@ -204,6 +204,7 @@ -- SKIP_LOCKED option VACUUM (SKIP_LOCKED) vactst; VACUUM (SKIP_LOCKED, FULL) vactst; +WARNING: skipping vacuum of "vactst" --- lock not available ANALYZE (SKIP_LOCKED) vactst; -- ensure VACUUM and ANALYZE don't have a problem with serializable SET default_transaction_isolation = serializable; No doubt this is a conflict with autovacuum. There are two reasonable ways to remove the test instability: * Crank up client_min_messages to more than WARNING for this test stanza. * Downgrade the "skipping" messages to DEBUG1 or less. I kind of wonder why we are issuing a "WARNING" when the statement does exactly what you asked it to, anyway. At most I'd expect that to be a NOTICE condition. regards, tom lane