Move test for BRIN HOT behavior to stats.sql

The test added by 5753d4ee32 relies on statistics collector, and so it
may occasionally fail when the UDP packet gets lost. Some machines may
be susceptible to this, probably depending on load etc.

Move the test to stats.sql, which is known to already have this issue
and people know to ignore it.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/CAFp7QwpMRGcDAQumN7onN9HjrJ3u4X3ZRXdGFT0K5G2JWvnbWg%40mail.gmail.com

src/test/regress/expected/brin.out

@@ -567,56 +567,7 @@ SELECT * FROM brintest_3 WHERE b < '0';
 
 DROP TABLE brintest_3;
 RESET enable_seqscan;
--- test BRIN index doesn't block HOT update
-CREATE TABLE brin_hot (
-        id  integer PRIMARY KEY,
-        val integer NOT NULL
-) WITH (autovacuum_enabled = off, fillfactor = 70);
-INSERT INTO brin_hot SELECT *, 0 FROM generate_series(1, 235);
-CREATE INDEX val_brin ON brin_hot using brin(val);
-CREATE FUNCTION wait_for_hot_stats() RETURNS void AS $$
-DECLARE
-        start_time timestamptz := clock_timestamp();
-        updated bool;
-BEGIN
-        -- we don't want to wait forever; loop will exit after 30 seconds
-        FOR i IN 1 .. 300 LOOP
-                SELECT (pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid) > 0) INTO updated;
-                EXIT WHEN updated;
-
-                -- wait a little
-                PERFORM pg_sleep_for('100 milliseconds');
-                -- reset stats snapshot so we can test again
-                PERFORM pg_stat_clear_snapshot();
-        END LOOP;
-        -- report time waited in postmaster log (where it won't change test output)
-        RAISE log 'wait_for_hot_stats delayed % seconds',
-          EXTRACT(epoch FROM clock_timestamp() - start_time);
-END
-$$ LANGUAGE plpgsql;
-UPDATE brin_hot SET val = -3 WHERE id = 42;
--- We can't just call wait_for_hot_stats() at this point, because we only
--- transmit stats when the session goes idle, and we probably didn't
--- transmit the last couple of counts yet thanks to the rate-limiting logic
--- in pgstat_report_stat().  But instead of waiting for the rate limiter's
--- timeout to elapse, let's just start a new session.  The old one will
--- then send its stats before dying.
-\c -
-SELECT wait_for_hot_stats();
- wait_for_hot_stats 
---------------------
- 
-(1 row)
-
-SELECT pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid);
- pg_stat_get_tuples_hot_updated 
---------------------------------
-                              1
-(1 row)
-
-DROP TABLE brin_hot;
-DROP FUNCTION wait_for_hot_stats();
--- Test handling of index predicates - updating attributes in precicates
+-- Test handling of index predicates - updating attributes in predicates
 -- should block HOT even for BRIN. We update a row that was not indexed
 -- due to the index predicate, and becomes indexable.
 CREATE TABLE brin_hot_2 (a int, b int);

src/test/regress/expected/stats.out

@@ -201,4 +201,55 @@ FROM prevstats AS pr;
 
 DROP TABLE trunc_stats_test, trunc_stats_test1, trunc_stats_test2, trunc_stats_test3, trunc_stats_test4;
 DROP TABLE prevstats;
+-- test BRIN index doesn't block HOT update - we include this test here, as it
+-- relies on statistics collector and so it may occasionally fail, especially
+-- on slower systems
+CREATE TABLE brin_hot (
+        id  integer PRIMARY KEY,
+        val integer NOT NULL
+) WITH (autovacuum_enabled = off, fillfactor = 70);
+INSERT INTO brin_hot SELECT *, 0 FROM generate_series(1, 235);
+CREATE INDEX val_brin ON brin_hot using brin(val);
+CREATE FUNCTION wait_for_hot_stats() RETURNS void AS $$
+DECLARE
+        start_time timestamptz := clock_timestamp();
+        updated bool;
+BEGIN
+        -- we don't want to wait forever; loop will exit after 30 seconds
+        FOR i IN 1 .. 300 LOOP
+                SELECT (pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid) > 0) INTO updated;
+                EXIT WHEN updated;
+
+                -- wait a little
+                PERFORM pg_sleep_for('100 milliseconds');
+                -- reset stats snapshot so we can test again
+                PERFORM pg_stat_clear_snapshot();
+        END LOOP;
+        -- report time waited in postmaster log (where it won't change test output)
+        RAISE log 'wait_for_hot_stats delayed % seconds',
+          EXTRACT(epoch FROM clock_timestamp() - start_time);
+END
+$$ LANGUAGE plpgsql;
+UPDATE brin_hot SET val = -3 WHERE id = 42;
+-- We can't just call wait_for_hot_stats() at this point, because we only
+-- transmit stats when the session goes idle, and we probably didn't
+-- transmit the last couple of counts yet thanks to the rate-limiting logic
+-- in pgstat_report_stat().  But instead of waiting for the rate limiter's
+-- timeout to elapse, let's just start a new session.  The old one will
+-- then send its stats before dying.
+\c -
+SELECT wait_for_hot_stats();
+ wait_for_hot_stats 
+--------------------
+ 
+(1 row)
+
+SELECT pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid);
+ pg_stat_get_tuples_hot_updated 
+--------------------------------
+                              1
+(1 row)
+
+DROP TABLE brin_hot;
+DROP FUNCTION wait_for_hot_stats();
 -- End of Stats Test

src/test/regress/sql/brin.sql

@@ -510,53 +510,7 @@ SELECT * FROM brintest_3 WHERE b < '0';
 DROP TABLE brintest_3;
 RESET enable_seqscan;
 
--- test BRIN index doesn't block HOT update
-CREATE TABLE brin_hot (
-        id  integer PRIMARY KEY,
-        val integer NOT NULL
-) WITH (autovacuum_enabled = off, fillfactor = 70);
-
-INSERT INTO brin_hot SELECT *, 0 FROM generate_series(1, 235);
-CREATE INDEX val_brin ON brin_hot using brin(val);
-
-CREATE FUNCTION wait_for_hot_stats() RETURNS void AS $$
-DECLARE
-        start_time timestamptz := clock_timestamp();
-        updated bool;
-BEGIN
-        -- we don't want to wait forever; loop will exit after 30 seconds
-        FOR i IN 1 .. 300 LOOP
-                SELECT (pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid) > 0) INTO updated;
-                EXIT WHEN updated;
-
-                -- wait a little
-                PERFORM pg_sleep_for('100 milliseconds');
-                -- reset stats snapshot so we can test again
-                PERFORM pg_stat_clear_snapshot();
-        END LOOP;
-        -- report time waited in postmaster log (where it won't change test output)
-        RAISE log 'wait_for_hot_stats delayed % seconds',
-          EXTRACT(epoch FROM clock_timestamp() - start_time);
-END
-$$ LANGUAGE plpgsql;
-
-UPDATE brin_hot SET val = -3 WHERE id = 42;
-
--- We can't just call wait_for_hot_stats() at this point, because we only
--- transmit stats when the session goes idle, and we probably didn't
--- transmit the last couple of counts yet thanks to the rate-limiting logic
--- in pgstat_report_stat().  But instead of waiting for the rate limiter's
--- timeout to elapse, let's just start a new session.  The old one will
--- then send its stats before dying.
-\c -
-
-SELECT wait_for_hot_stats();
-SELECT pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid);
-
-DROP TABLE brin_hot;
-DROP FUNCTION wait_for_hot_stats();
-
--- Test handling of index predicates - updating attributes in precicates
+-- Test handling of index predicates - updating attributes in predicates
 -- should block HOT even for BRIN. We update a row that was not indexed
 -- due to the index predicate, and becomes indexable.
 CREATE TABLE brin_hot_2 (a int, b int);

src/test/regress/sql/stats.sql

@@ -176,4 +176,54 @@ FROM prevstats AS pr;
 
 DROP TABLE trunc_stats_test, trunc_stats_test1, trunc_stats_test2, trunc_stats_test3, trunc_stats_test4;
 DROP TABLE prevstats;
+
+-- test BRIN index doesn't block HOT update - we include this test here, as it
+-- relies on statistics collector and so it may occasionally fail, especially
+-- on slower systems
+CREATE TABLE brin_hot (
+        id  integer PRIMARY KEY,
+        val integer NOT NULL
+) WITH (autovacuum_enabled = off, fillfactor = 70);
+
+INSERT INTO brin_hot SELECT *, 0 FROM generate_series(1, 235);
+CREATE INDEX val_brin ON brin_hot using brin(val);
+
+CREATE FUNCTION wait_for_hot_stats() RETURNS void AS $$
+DECLARE
+        start_time timestamptz := clock_timestamp();
+        updated bool;
+BEGIN
+        -- we don't want to wait forever; loop will exit after 30 seconds
+        FOR i IN 1 .. 300 LOOP
+                SELECT (pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid) > 0) INTO updated;
+                EXIT WHEN updated;
+
+                -- wait a little
+                PERFORM pg_sleep_for('100 milliseconds');
+                -- reset stats snapshot so we can test again
+                PERFORM pg_stat_clear_snapshot();
+        END LOOP;
+        -- report time waited in postmaster log (where it won't change test output)
+        RAISE log 'wait_for_hot_stats delayed % seconds',
+          EXTRACT(epoch FROM clock_timestamp() - start_time);
+END
+$$ LANGUAGE plpgsql;
+
+UPDATE brin_hot SET val = -3 WHERE id = 42;
+
+-- We can't just call wait_for_hot_stats() at this point, because we only
+-- transmit stats when the session goes idle, and we probably didn't
+-- transmit the last couple of counts yet thanks to the rate-limiting logic
+-- in pgstat_report_stat().  But instead of waiting for the rate limiter's
+-- timeout to elapse, let's just start a new session.  The old one will
+-- then send its stats before dying.
+\c -
+
+SELECT wait_for_hot_stats();
+SELECT pg_stat_get_tuples_hot_updated('brin_hot'::regclass::oid);
+
+DROP TABLE brin_hot;
+DROP FUNCTION wait_for_hot_stats();
+
+
 -- End of Stats Test