Improve stability of tests for VACUUM (SKIP_LOCKED)

Concurrent autovacuums running with the main regression test suite
could cause the tests with VACUUM (SKIP_LOCKED) to generate randomly
WARNING messages.  For these tests, set client_min_messages to ERROR to
get rid of those random failures, as disabling autovacuum for the
relations operated would not completely close the failure window.

For isolation tests, disable autovacuum for the relations vacuumed with
SKIP_LOCKED.  The tests are designed so as LOCK commands are taken
in a first session before running a concurrent VACUUM (SKIP_LOCKED) in a
second to generate WARNING messages, but a concurrent autovacuum could
cause the tests to be slower.

Reported-by: Tom Lane
Author: Michael Paquier
Reviewed-by: Andres Freund, Tom Lane
Discussion: https://postgr.es/m/25294.1573077278@sss.pgh.pa.us
Backpatch-through: 12

src/test/isolation/specs/vacuum-skip-locked.spec

@@ -7,7 +7,9 @@ setup
 {
 	CREATE TABLE parted (a INT) PARTITION BY LIST (a);
 	CREATE TABLE part1 PARTITION OF parted FOR VALUES IN (1);
+	ALTER TABLE part1 SET (autovacuum_enabled = false);
 	CREATE TABLE part2 PARTITION OF parted FOR VALUES IN (2);
+	ALTER TABLE part2 SET (autovacuum_enabled = false);
 }
 
 teardown

src/test/regress/expected/vacuum.out

@@ -196,7 +196,9 @@ ERROR:  unrecognized ANALYZE option "nonexistentarg"
 LINE 1: ANALYZE (nonexistentarg) does_not_exit;
                  ^
 -- ensure argument order independence, and that SKIP_LOCKED on non-existing
--- relation still errors out.
+-- relation still errors out.  Suppress WARNING messages caused by concurrent
+-- autovacuums.
+SET client_min_messages TO 'ERROR';
 ANALYZE (SKIP_LOCKED, VERBOSE) does_not_exist;
 ERROR:  relation "does_not_exist" does not exist
 ANALYZE (VERBOSE, SKIP_LOCKED) does_not_exist;
@@ -205,6 +207,7 @@ ERROR:  relation "does_not_exist" does not exist
 VACUUM (SKIP_LOCKED) vactst;
 VACUUM (SKIP_LOCKED, FULL) vactst;
 ANALYZE (SKIP_LOCKED) vactst;
+RESET client_min_messages;
 -- ensure VACUUM and ANALYZE don't have a problem with serializable
 SET default_transaction_isolation = serializable;
 VACUUM vactst;

src/test/regress/sql/vacuum.sql

@@ -158,7 +158,9 @@ ANALYZE (nonexistent-arg) does_not_exist;
 ANALYZE (nonexistentarg) does_not_exit;
 
 -- ensure argument order independence, and that SKIP_LOCKED on non-existing
--- relation still errors out.
+-- relation still errors out.  Suppress WARNING messages caused by concurrent
+-- autovacuums.
+SET client_min_messages TO 'ERROR';
 ANALYZE (SKIP_LOCKED, VERBOSE) does_not_exist;
 ANALYZE (VERBOSE, SKIP_LOCKED) does_not_exist;
 
@@ -166,6 +168,7 @@ ANALYZE (VERBOSE, SKIP_LOCKED) does_not_exist;
 VACUUM (SKIP_LOCKED) vactst;
 VACUUM (SKIP_LOCKED, FULL) vactst;
 ANALYZE (SKIP_LOCKED) vactst;
+RESET client_min_messages;
 
 -- ensure VACUUM and ANALYZE don't have a problem with serializable
 SET default_transaction_isolation = serializable;