pgstat: test stats interactions with physical replication.

Tests that standbys:
- drop stats for objects when the those records are replayed
- persist stats across graceful restarts
- discard stats after immediate / crash restarts

Author: Melanie Plageman <melanieplageman@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de

src/test/recovery/t/030_stats_cleanup_replica.pl

@@ -0,0 +1,206 @@
+# Copyright (c) 2021-2022, PostgreSQL Global Development Group
+
+# Tests that standbys:
+# - drop stats for objects when the those records are replayed
+# - persist stats across graceful restarts
+# - discard stats after immediate / crash restarts
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my $node_primary = PostgreSQL::Test::Cluster->new('primary');
+$node_primary->init(allows_streaming => 1);
+$node_primary->append_conf('postgresql.conf', "track_functions = 'all'");
+$node_primary->start;
+
+my $backup_name = 'my_backup';
+$node_primary->backup($backup_name);
+
+my $node_standby = PostgreSQL::Test::Cluster->new('standby');
+$node_standby->init_from_backup($node_primary, $backup_name,
+	has_streaming => 1);
+$node_standby->start;
+
+
+## Test that stats are cleaned up on standby after dropping table or function
+
+my $sect = 'initial';
+
+my ($dboid, $tableoid, $funcoid) =
+  populate_standby_stats('postgres', 'public');
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 't');
+
+drop_table_by_oid('postgres', $tableoid);
+drop_function_by_oid('postgres', $funcoid);
+
+$sect = 'post drop';
+my $primary_lsn = $node_primary->lsn('flush');
+$node_primary->wait_for_catchup($node_standby, 'replay', $primary_lsn);
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 'f');
+
+
+## Test that stats are cleaned up on standby after dropping indirectly
+
+$sect = "schema creation";
+
+$node_primary->safe_psql('postgres', "CREATE SCHEMA drop_schema_test1");
+$primary_lsn = $node_primary->lsn('flush');
+$node_primary->wait_for_catchup($node_standby, 'replay', $primary_lsn);
+
+($dboid, $tableoid, $funcoid) =
+  populate_standby_stats('postgres', 'drop_schema_test1');
+
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 't');
+$node_primary->safe_psql('postgres', "DROP SCHEMA drop_schema_test1 CASCADE");
+
+$sect = "post schema drop";
+
+$primary_lsn = $node_primary->lsn('flush');
+$node_primary->wait_for_catchup($node_standby, 'replay', $primary_lsn);
+
+# verify table and function stats removed from standby
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 'f');
+
+
+## Test that stats are cleaned up on standby after dropping database
+
+$sect = "createdb";
+
+$node_primary->safe_psql('postgres', "CREATE DATABASE test");
+$primary_lsn = $node_primary->lsn('flush');
+$node_primary->wait_for_catchup($node_standby, 'replay', $primary_lsn);
+
+($dboid, $tableoid, $funcoid) = populate_standby_stats('test', 'public');
+
+# verify stats are present
+test_standby_func_tab_stats_status('test', $dboid, $tableoid, $funcoid, 't');
+test_standby_db_stats_status('test', $dboid, 't');
+
+$node_primary->safe_psql('postgres', "DROP DATABASE test");
+$sect        = "post dropdb";
+$primary_lsn = $node_primary->lsn('flush');
+$node_primary->wait_for_catchup($node_standby, 'replay', $primary_lsn);
+
+# Test that the stats were cleaned up on standby
+# Note that this connects to 'postgres' but provides the dboid of dropped db
+# 'test' which we acquired previously
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 'f');
+
+test_standby_db_stats_status('postgres', $dboid, 'f');
+
+
+## verify that stats persist across graceful restarts on a replica
+
+# NB: Can't test database stats, they're immediately repopulated when
+# reconnecting...
+$sect = "pre restart";
+($dboid, $tableoid, $funcoid) = populate_standby_stats('postgres', 'public');
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 't');
+
+$node_standby->restart();
+
+$sect = "post non-immediate";
+
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 't');
+
+# but gone after an immediate restart
+$node_standby->stop('immediate');
+$node_standby->start();
+
+$sect = "post immediate restart";
+
+test_standby_func_tab_stats_status('postgres',
+	$dboid, $tableoid, $funcoid, 'f');
+
+
+done_testing();
+
+
+sub populate_standby_stats
+{
+	my ($connect_db, $schema) = @_;
+
+	# create objects on primary
+	$node_primary->safe_psql($connect_db,
+		"CREATE TABLE $schema.drop_tab_test1 AS SELECT generate_series(1,100) AS a"
+	);
+	$node_primary->safe_psql($connect_db,
+		"CREATE FUNCTION $schema.drop_func_test1() RETURNS VOID AS 'select 2;' LANGUAGE SQL IMMUTABLE"
+	);
+	my $primary_lsn = $node_primary->lsn('flush');
+	$node_primary->wait_for_catchup($node_standby, 'replay', $primary_lsn);
+
+	# collect object oids
+	my $dboid = $node_standby->safe_psql($connect_db,
+		"SELECT oid FROM pg_database WHERE datname = '$connect_db'");
+	my $tableoid = $node_standby->safe_psql($connect_db,
+		"SELECT '$schema.drop_tab_test1'::regclass::oid");
+	my $funcoid = $node_standby->safe_psql($connect_db,
+		"SELECT '$schema.drop_func_test1()'::regprocedure::oid");
+
+	# generate stats on standby
+	$node_standby->safe_psql($connect_db,
+		"SELECT * FROM $schema.drop_tab_test1");
+	$node_standby->safe_psql($connect_db, "SELECT $schema.drop_func_test1()");
+
+	return ($dboid, $tableoid, $funcoid);
+}
+
+sub drop_function_by_oid
+{
+	my ($connect_db, $funcoid) = @_;
+
+	# Get function name from returned oid
+	my $func_name = $node_primary->safe_psql($connect_db,
+		"SELECT '$funcoid'::regprocedure");
+	$node_primary->safe_psql($connect_db, "DROP FUNCTION $func_name");
+}
+
+sub drop_table_by_oid
+{
+	my ($connect_db, $tableoid) = @_;
+
+	# Get table name from returned oid
+	my $table_name =
+	  $node_primary->safe_psql($connect_db, "SELECT '$tableoid'::regclass");
+	$node_primary->safe_psql($connect_db, "DROP TABLE $table_name");
+}
+
+sub test_standby_func_tab_stats_status
+{
+	local $Test::Builder::Level = $Test::Builder::Level + 1;
+	my ($connect_db, $dboid, $tableoid, $funcoid, $present) = @_;
+
+	my %expected = (rel => $present, func => $present);
+	my %stats;
+
+	$stats{rel} = $node_standby->safe_psql($connect_db,
+		"SELECT pg_stat_have_stats('relation', $dboid, $tableoid)");
+	$stats{func} = $node_standby->safe_psql($connect_db,
+		"SELECT pg_stat_have_stats('function', $dboid, $funcoid)");
+
+	is_deeply(\%stats, \%expected, "$sect: standby stats as expected");
+
+	return;
+}
+
+sub test_standby_db_stats_status
+{
+	local $Test::Builder::Level = $Test::Builder::Level + 1;
+	my ($connect_db, $dboid, $present) = @_;
+
+	is( $node_standby->safe_psql(
+			$connect_db, "SELECT pg_stat_have_stats('database', $dboid, 0)"),
+		$present,
+		"$sect: standby db stats as expected");
+}