OK, here's a v4:

* It works with 002_pg_upgrade.pl now.  The only substantive change
I had to make for that was to define the $old_version arguments as
being always PostgreSQL::Version objects not strings, because
otherwise I got complaints like

Argument "HEAD" isn't numeric in numeric comparison (<=>) at 
/home/postgres/pgsql/src/bin/pg_upgrade/../../../src/test/perl/PostgreSQL/Version.pm
 line 130.

So now TestUpgradeXversion.pm is responsible for performing that
conversion, and also for not doing any conversions on HEAD (which
Andrew wanted anyway).

* I improved pg_upgrade's TESTING directions after figuring out how
to get it to work for contrib modules.

* Incorporated (most of) Andrew's stylistic improvements.

* Simplified TestUpgradeXversion.pm's use of diff, as discussed.

I think we're about ready to go, except for cutting down
AdjustUpgrade.pm to make versions to put in the back branches.

I'm slightly tempted to back-patch 002_pg_upgrade.pl so that there
is an in-tree way to verify back-branch AdjustUpgrade.pm files.
On the other hand, it's hard to believe that testing that in
HEAD won't be sufficient; I doubt the back-branch copies will
need to change much.

                        regards, tom lane

diff --git a/src/bin/pg_upgrade/TESTING b/src/bin/pg_upgrade/TESTING
index 98286231d7..81a4324a76 100644
--- a/src/bin/pg_upgrade/TESTING
+++ b/src/bin/pg_upgrade/TESTING
@@ -10,31 +10,14 @@ This will run the TAP tests to run pg_upgrade, performing an upgrade
 from the version in this source tree to a new instance of the same
 version.
 
-Testing an upgrade from a different version requires a dump to set up
-the contents of this instance, with its set of binaries.  The following
-variables are available to control the test (see DETAILS below about
-the creation of the dump):
+Testing an upgrade from a different PG version is also possible, and
+provides a more thorough test that pg_upgrade does what it's meant for.
+This requires both a source tree and an installed tree for the old
+version, as well as a dump file to set up the instance to be upgraded.
+The following environment variables must be set to enable this testing:
 export olddump=...somewhere/dump.sql	(old version's dump)
 export oldinstall=...otherversion/	(old version's install base path)
-
-"filter_rules" is a variable that can be used to specify a file with custom
-filtering rules applied before comparing the dumps of the PostgreSQL
-instances near the end of the tests, in the shape of regular expressions
-valid for perl.  This is useful to enforce certain validation cases where
-pg_dump could create inconsistent outputs across major versions.
-For example:
-
-	# Remove all CREATE POLICY statements
-	s/^CREATE\sPOLICY.*//mgx
-	# Replace REFRESH with DROP for materialized views
-	s/^REFRESH\s(MATERIALIZED\sVIEW)/DROP $1/mgx
-
-Lines beginning with '#' and empty lines are ignored.  One rule can be
-defined per line.
-
-Finally, the tests can be done by running
-
-	make check
+See DETAILS below for more information about creation of the dump.
 
 You can also test the different transfer modes (--copy, --link,
 --clone) by setting the environment variable PG_TEST_PG_UPGRADE_MODE
@@ -52,22 +35,32 @@ The most effective way to test pg_upgrade, aside from testing on user
 data, is by upgrading the PostgreSQL regression database.
 
 This testing process first requires the creation of a valid regression
-database dump that can be then used for $olddump.  Such files contain
+database dump that can then be used for $olddump.  Such files contain
 most database features and are specific to each major version of Postgres.
 
 Here are the steps needed to create a dump file:
 
 1)  Create and populate the regression database in the old cluster.
     This database can be created by running 'make installcheck' from
-    src/test/regress using its source code tree.
+    src/test/regress in the old version's source code tree.
 
-2)  Use pg_dumpall to dump out the contents of the instance, including the
-    regression database, in the shape of a SQL file.  This requires the *old*
-    cluster's pg_dumpall so as the dump created is compatible with the
-    version of the cluster it is dumped into.
+    If you like, you can also populate regression databases for one or
+    more contrib modules by running 'make installcheck USE_MODULE_DB=1'
+    in their directories.  (USE_MODULE_DB is essential so that the
+    pg_upgrade test script will understand which database is which.)
 
-Once the dump is created, it can be repeatedly used with $olddump and
-`make check`, that automates the dump of the old database, its upgrade,
-the dump out of the new database and the comparison of the dumps between
-the old and new databases.  The contents of the dumps can also be manually
-compared.
+2)  Use pg_dumpall to dump out the contents of the instance, including the
+    regression database(s), into a SQL file.  Use the *old* version's
+    pg_dumpall so that the dump created is compatible with that version.
+
+Once the dump file is created, it can be used repeatedly.  Set $olddump
+to point to the dump file and run 'make check' or 'make installcheck'
+in the new version's src/bin/pg_upgrade directory.  (If you included any
+contrib databases in the old dump, you must use 'make installcheck' and
+ensure that the corresponding contrib modules have been installed in
+the new version's installation tree.)  This will build a temporary cluster
+using the old installation's executables, populate it from the dump file,
+and then try to pg_upgrade it to the new version.  Success is reported
+if pg_dumpall output matches between the pre-upgrade and post-upgrade
+databases.  In case of trouble, manually comparing those dump files may
+help to isolate the problem.
diff --git a/src/bin/pg_upgrade/t/002_pg_upgrade.pl b/src/bin/pg_upgrade/t/002_pg_upgrade.pl
index c066fd7d93..62a8fa9d8b 100644
--- a/src/bin/pg_upgrade/t/002_pg_upgrade.pl
+++ b/src/bin/pg_upgrade/t/002_pg_upgrade.pl
@@ -10,6 +10,7 @@ use File::Path qw(rmtree);
 
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::AdjustUpgrade;
 use Test::More;
 
 # Can be changed to test the other modes.
@@ -37,37 +38,16 @@ sub generate_db
 # This returns the path to the filtered dump.
 sub filter_dump
 {
-	my ($node, $dump_file) = @_;
+	my ($is_old, $old_version, $dump_file) = @_;
 	my $dump_contents = slurp_file($dump_file);
 
-	# Remove the comments.
-	$dump_contents =~ s/^\-\-.*//mgx;
-	# Remove empty lines.
-	$dump_contents =~ s/^\n//mgx;
-
-	# Apply custom filtering rules, if any.
-	if (defined($ENV{filter_rules}))
+	if ($is_old)
 	{
-		my $filter_file = $ENV{filter_rules};
-		die "no file with custom filter rules found!" unless -e $filter_file;
-
-		open my $filter_handle, '<', $filter_file
-		  or die "could not open $filter_file";
-		while (<$filter_handle>)
-		{
-			my $filter_line = $_;
-
-			# Skip comments and empty lines
-			next if ($filter_line =~ /^#/);
-			next if ($filter_line =~ /^\s*$/);
-
-			# Apply lines with filters.
-			note "Applying custom rule $filter_line to $dump_file";
-			my $filter = "\$dump_contents =~ $filter_line";
-			## no critic (ProhibitStringyEval)
-			eval $filter;
-		}
-		close $filter_handle;
+		$dump_contents = adjust_old_dumpfile($old_version, $dump_contents);
+	}
+	else
+	{
+		$dump_contents = adjust_new_dumpfile($old_version, $dump_contents);
 	}
 
 	my $dump_file_filtered = "${dump_file}_filtered";
@@ -83,7 +63,7 @@ sub filter_dump
 # that gets upgraded.  Before running the upgrade, a logical dump of the
 # old cluster is taken, and a second logical dump of the new one is taken
 # after the upgrade.  The upgrade test passes if there are no differences
-# in these two dumps.
+# (after filtering) in these two dumps.
 
 # Testing upgrades with an older version of PostgreSQL requires setting up
 # two environment variables, as of:
@@ -198,15 +178,29 @@ my $oldbindir = $oldnode->config_data('--bindir');
 # only if different major versions are used for the dump.
 if (defined($ENV{oldinstall}))
 {
-	# Note that upgrade_adapt.sql and psql from the new version are used,
-	# to cope with an upgrade to this version.
-	$newnode->command_ok(
-		[
-			'psql', '-X',
-			'-f',   "$srcdir/src/bin/pg_upgrade/upgrade_adapt.sql",
-			'-d',   $oldnode->connstr('regression'),
-		],
-		'ran adapt script');
+	# Consult AdjustUpgrade to find out what we need to do.
+	my $dbnames =
+	  $oldnode->safe_psql('postgres', qq(SELECT datname FROM pg_database));
+	my %dbnames;
+	do { $dbnames{$_} = 1; }
+	  foreach split /\s+/s, $dbnames;
+	my $adjust_cmds =
+	  adjust_database_contents($oldnode->pg_version, %dbnames);
+
+	foreach my $updb (keys %$adjust_cmds)
+	{
+		my $upcmds = join(";\n", @{ $adjust_cmds->{$updb} });
+
+		# For simplicity, use the newer version's psql to issue the commands.
+		$newnode->command_ok(
+			[
+				'psql', '-X',
+				'-v',   'ON_ERROR_STOP=1',
+				'-c',   $upcmds,
+				'-d',   $oldnode->connstr($updb),
+			],
+			"ran version adaptation commands for database $updb");
+	}
 }
 
 # Take a dump before performing the upgrade as a base comparison. Note
@@ -359,8 +353,8 @@ my $dump1_filtered = $dump1_file;
 my $dump2_filtered = $dump2_file;
 if ($oldnode->pg_version != $newnode->pg_version)
 {
-	$dump1_filtered = filter_dump($oldnode, $dump1_file);
-	$dump2_filtered = filter_dump($newnode, $dump2_file);
+	$dump1_filtered = filter_dump(1, $oldnode->pg_version, $dump1_file);
+	$dump2_filtered = filter_dump(0, $oldnode->pg_version, $dump2_file);
 }
 
 # Compare the two dumps, there should be no differences.
@@ -371,7 +365,7 @@ is($compare_res, 0, 'old and new dumps match after pg_upgrade');
 if ($compare_res != 0)
 {
 	my ($stdout, $stderr) =
-	  run_command([ 'diff', $dump1_filtered, $dump2_filtered ]);
+	  run_command([ 'diff', '-u', $dump1_filtered, $dump2_filtered ]);
 	print "=== diff of $dump1_filtered and $dump2_filtered\n";
 	print "=== stdout ===\n";
 	print $stdout;
diff --git a/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm b/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm
new file mode 100644
index 0000000000..7b4a19be2a
--- /dev/null
+++ b/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm
@@ -0,0 +1,524 @@
+
+# Copyright (c) 2023, PostgreSQL Global Development Group
+
+=pod
+
+=head1 NAME
+
+PostgreSQL::Test::AdjustUpgrade - helper module for cross-version upgrade tests
+
+=head1 SYNOPSIS
+
+  use PostgreSQL::Test::AdjustUpgrade;
+
+  # Build commands to adjust contents of old-version database before dumping
+  $statements = adjust_database_contents($old_version, %dbnames);
+
+  # Adjust contents of old pg_dumpall output file to match newer version
+  $dump = adjust_old_dumpfile($old_version, $dump);
+
+  # Adjust contents of new pg_dumpall output file to match older version
+  $dump = adjust_new_dumpfile($old_version, $dump);
+
+=head1 DESCRIPTION
+
+C<PostgreSQL::Test::AdjustUpgrade> encapsulates various hacks needed to
+compare the results of cross-version upgrade tests.
+
+=cut
+
+package PostgreSQL::Test::AdjustUpgrade;
+
+use strict;
+use warnings;
+
+use Exporter 'import';
+use PostgreSQL::Version;
+
+our @EXPORT = qw(
+  adjust_database_contents
+  adjust_old_dumpfile
+  adjust_new_dumpfile
+);
+
+=pod
+
+=head1 ROUTINES
+
+=over
+
+=item $statements = adjust_database_contents($old_version, %dbnames)
+
+Generate SQL commands to perform any changes to an old-version installation
+that are needed before we can pg_upgrade it into the current PostgreSQL
+version.
+
+Typically this involves dropping or adjusting no-longer-supported objects.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from, represented as a
+PostgreSQL::Version object.
+
+=item C<dbnames>: Hash of database names present in the old installation.
+
+=back
+
+Returns a reference to a hash, wherein the keys are database names and the
+values are arrayrefs to lists of statements to be run in those databases.
+
+=cut
+
+sub adjust_database_contents
+{
+	my ($old_version, %dbnames) = @_;
+	my $result = {};
+
+	# remove dbs of modules known to cause pg_upgrade to fail
+	# anything not builtin and incompatible should clean up its own db
+	foreach my $bad_module ('test_ddl_deparse', 'tsearch2')
+	{
+		if ($dbnames{"contrib_regression_$bad_module"})
+		{
+			_add_st($result, 'postgres',
+				"drop database contrib_regression_$bad_module");
+			delete($dbnames{"contrib_regression_$bad_module"});
+		}
+	}
+
+	# avoid version number issues with test_ext7
+	if ($dbnames{contrib_regression_test_extensions})
+	{
+		_add_st(
+			$result,
+			'contrib_regression_test_extensions',
+			'drop extension if exists test_ext7');
+	}
+
+	# stuff not supported from release 16
+	if ($old_version >= 12 && $old_version < 16)
+	{
+		# Can't upgrade aclitem in user tables from pre 16 to 16+.
+		_add_st($result, 'regression',
+			'alter table public.tab_core_types drop column aclitem');
+		# Can't handle child tables with locally-generated columns.
+		_add_st(
+			$result, 'regression',
+			'drop table public.gtest_normal_child',
+			'drop table public.gtest_normal_child2');
+	}
+
+	# stuff not supported from release 14
+	if ($old_version < 14)
+	{
+		# postfix operators (some don't exist in very old versions)
+		_add_st(
+			$result,
+			'regression',
+			'drop operator #@# (bigint,NONE)',
+			'drop operator #%# (bigint,NONE)',
+			'drop operator if exists !=- (bigint,NONE)',
+			'drop operator if exists #@%# (bigint,NONE)');
+
+		# get rid of dblink's dependencies on regress.so
+		my $regrdb =
+		  $old_version le '9.4'
+		  ? 'contrib_regression'
+		  : 'contrib_regression_dblink';
+
+		if ($dbnames{$regrdb})
+		{
+			_add_st(
+				$result, $regrdb,
+				'drop function if exists public.putenv(text)',
+				'drop function if exists public.wait_pid(integer)');
+		}
+	}
+
+	# user table OIDs are gone from release 12 on
+	if ($old_version < 12)
+	{
+		my $nooid_stmt = q{
+           DO $stmt$
+           DECLARE
+              rec text;
+           BEGIN
+              FOR rec in
+                 select oid::regclass::text
+                 from pg_class
+                 where relname !~ '^pg_'
+                    and relhasoids
+                    and relkind in ('r','m')
+                 order by 1
+              LOOP
+                 execute 'ALTER TABLE ' || rec || ' SET WITHOUT OIDS';
+                 RAISE NOTICE 'removing oids from table %', rec;
+              END LOOP;
+           END; $stmt$;
+        };
+
+		foreach my $oiddb ('regression', 'contrib_regression_btree_gist')
+		{
+			next unless $dbnames{$oiddb};
+			_add_st($result, $oiddb, $nooid_stmt);
+		}
+
+		# this table had OIDs too, but we'll just drop it
+		if ($old_version >= 10 && $dbnames{'contrib_regression_postgres_fdw'})
+		{
+			_add_st(
+				$result,
+				'contrib_regression_postgres_fdw',
+				'drop foreign table ft_pg_type');
+		}
+	}
+
+	# abstime+friends are gone from release 12 on; but these tables
+	# might or might not be present depending on regression test vintage
+	if ($old_version < 12)
+	{
+		_add_st($result, 'regression',
+			'drop table if exists abstime_tbl, reltime_tbl, tinterval_tbl');
+	}
+
+	# some regression functions gone from release 11 on
+	if ($old_version < 11)
+	{
+		_add_st(
+			$result, 'regression',
+			'drop function if exists public.boxarea(box)',
+			'drop function if exists public.funny_dup17()');
+	}
+
+	# version-0 C functions are no longer supported
+	if ($old_version < 10)
+	{
+		_add_st($result, 'regression',
+			'drop function oldstyle_length(integer, text)');
+	}
+
+	if ($old_version lt '9.5')
+	{
+		# cope with changes of underlying functions
+		_add_st(
+			$result,
+			'regression',
+			'drop operator @#@ (NONE, bigint)',
+			'CREATE OPERATOR @#@ ('
+			  . 'PROCEDURE = factorial, RIGHTARG = bigint )',
+			'drop aggregate public.array_cat_accum(anyarray)',
+			'CREATE AGGREGATE array_larger_accum (anyarray) ' . ' ( '
+			  . '   sfunc = array_larger, '
+			  . '   stype = anyarray, '
+			  . '   initcond = $${}$$ ' . '  ) ');
+
+		# "=>" is no longer valid as an operator name
+		_add_st($result, 'regression',
+			'drop operator if exists public.=> (bigint, NONE)');
+	}
+
+	return $result;
+}
+
+# Internal subroutine to add statement(s) to the list for the given db.
+sub _add_st
+{
+	my ($result, $db, @st) = @_;
+
+	$result->{$db} ||= [];
+	push(@{ $result->{$db} }, @st);
+}
+
+=pod
+
+=item adjust_old_dumpfile($old_version, $dump)
+
+Edit a dump output file, taken from the adjusted old-version installation
+by current-version C<pg_dumpall -s>, so that it will match the results of
+C<pg_dumpall -s> on the pg_upgrade'd installation.
+
+Typically this involves coping with cosmetic differences in the output
+of backend subroutines used by pg_dump.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from, represented as a
+PostgreSQL::Version object.
+
+=item C<dump>: Contents of dump file
+
+=back
+
+Returns the modified dump text.
+
+=cut
+
+sub adjust_old_dumpfile
+{
+	my ($old_version, $dump) = @_;
+
+	# use Unix newlines
+	$dump =~ s/\r\n/\n/g;
+
+	# Version comments will certainly not match.
+	$dump =~ s/^-- Dumped from database version.*\n//mg;
+
+	if ($old_version >= 14 && $old_version < 16)
+	{
+		# Fix up some privilege-set discrepancies.
+		$dump =~
+		  s {^REVOKE SELECT,INSERT,REFERENCES,DELETE,TRIGGER,TRUNCATE,UPDATE ON TABLE}
+			{REVOKE ALL ON TABLE}mg;
+		$dump =~
+		  s {^(GRANT SELECT,INSERT,REFERENCES,TRIGGER,TRUNCATE),UPDATE ON TABLE}
+			{$1,MAINTAIN,UPDATE ON TABLE}mg;
+	}
+
+	if ($old_version < 14)
+	{
+		# Remove mentions of extended hash functions.
+		$dump =~ s {^(\s+OPERATOR\s1\s=\(integer,integer\))\s,\n
+                    \s+FUNCTION\s2\s\(integer,\sinteger\)\spublic\.part_hashint4_noop\(integer,bigint\);}
+				   {$1;}mxg;
+		$dump =~ s {^(\s+OPERATOR\s1\s=\(text,text\))\s,\n
+                    \s+FUNCTION\s2\s\(text,\stext\)\spublic\.part_hashtext_length\(text,bigint\);}
+				   {$1;}mxg;
+	}
+
+	# Change trigger definitions to say ... EXECUTE FUNCTION ...
+	if ($old_version < 12)
+	{
+		# would like to use lookbehind here but perl complains
+		# so do it this way
+		$dump =~ s/
+			(^CREATE\sTRIGGER\s.*?)
+			\sEXECUTE\sPROCEDURE
+			/$1 EXECUTE FUNCTION/mgx;
+	}
+
+	if ($old_version lt '9.6')
+	{
+		# adjust some places where we don't print so many parens anymore
+
+		my $prefix =
+		  "'New York'\tnew & york | big & apple | nyc\t'new' & 'york'\t";
+		my $orig = "( 'new' & 'york' | 'big' & 'appl' ) | 'nyc'";
+		my $repl = "'new' & 'york' | 'big' & 'appl' | 'nyc'";
+		$dump =~ s/(?<=^\Q$prefix\E)\Q$orig\E/$repl/mg;
+
+		$prefix =
+		  "'Sanct Peter'\tPeterburg | peter | 'Sanct Peterburg'\t'sanct' & 'peter'\t";
+		$orig = "( 'peterburg' | 'peter' ) | 'sanct' & 'peterburg'";
+		$repl = "'peterburg' | 'peter' | 'sanct' & 'peterburg'";
+		$dump =~ s/(?<=^\Q$prefix\E)\Q$orig\E/$repl/mg;
+	}
+
+	if ($old_version lt '9.5')
+	{
+		# adjust some places where we don't print so many parens anymore
+
+		my $prefix = "CONSTRAINT (?:sequence|copy)_con CHECK [(][(]";
+		my $orig   = "((x > 3) AND (y <> 'check failed'::text))";
+		my $repl   = "(x > 3) AND (y <> 'check failed'::text)";
+		$dump =~ s/($prefix)\Q$orig\E/$1$repl/mg;
+
+		$prefix = "CONSTRAINT insert_con CHECK [(][(]";
+		$orig   = "((x >= 3) AND (y <> 'check failed'::text))";
+		$repl   = "(x >= 3) AND (y <> 'check failed'::text)";
+		$dump =~ s/($prefix)\Q$orig\E/$1$repl/mg;
+
+		$orig = "DEFAULT ((-1) * currval('public.insert_seq'::regclass))";
+		$repl =
+		  "DEFAULT ('-1'::integer * currval('public.insert_seq'::regclass))";
+		$dump =~ s/\Q$orig\E/$repl/mg;
+
+		my $expr =
+		  "(rsl.sl_color = rsh.slcolor) AND (rsl.sl_len_cm >= rsh.slminlen_cm)";
+		$dump =~ s/WHERE \(\(\Q$expr\E\)/WHERE ($expr/g;
+
+		$expr =
+		  "(rule_and_refint_t3.id3a = new.id3a) AND (rule_and_refint_t3.id3b = new.id3b)";
+		$dump =~ s/WHERE \(\(\Q$expr\E\)/WHERE ($expr/g;
+
+		$expr =
+		  "(rule_and_refint_t3_1.id3a = new.id3a) AND (rule_and_refint_t3_1.id3b = new.id3b)";
+		$dump =~ s/WHERE \(\(\Q$expr\E\)/WHERE ($expr/g;
+	}
+
+	if ($old_version lt '9.3')
+	{
+		# CREATE VIEW/RULE statements were not pretty-printed before 9.3.
+		# To cope, reduce all whitespace sequences within them to one space.
+		# This must be done on both old and new dumps.
+		$dump = _mash_view_whitespace($dump);
+
+		# _mash_view_whitespace doesn't handle multi-command rules;
+		# rather than trying to fix that, just hack the exceptions manually.
+
+		my $prefix =
+		  "CREATE RULE rtest_sys_del AS ON DELETE TO public.rtest_system DO (DELETE FROM public.rtest_interface WHERE (rtest_interface.sysname = old.sysname);";
+		my $line2 = " DELETE FROM public.rtest_admin";
+		my $line3 = " WHERE (rtest_admin.sysname = old.sysname);";
+		$dump =~
+		  s/(?<=\Q$prefix\E)\Q$line2$line3\E \);/\n$line2\n $line3\n);/mg;
+
+		$prefix =
+		  "CREATE RULE rtest_sys_upd AS ON UPDATE TO public.rtest_system DO (UPDATE public.rtest_interface SET sysname = new.sysname WHERE (rtest_interface.sysname = old.sysname);";
+		$line2 = " UPDATE public.rtest_admin SET sysname = new.sysname";
+		$line3 = " WHERE (rtest_admin.sysname = old.sysname);";
+		$dump =~
+		  s/(?<=\Q$prefix\E)\Q$line2$line3\E \);/\n$line2\n $line3\n);/mg;
+
+		# and there's one place where pre-9.3 uses a different table alias
+		$dump =~ s {^(CREATE\sRULE\srule_and_refint_t3_ins\sAS\s
+			 ON\sINSERT\sTO\spublic\.rule_and_refint_t3\s
+			 WHERE\s\(EXISTS\s\(SELECT\s1\sFROM\spublic\.rule_and_refint_t3)\s
+			 (WHERE\s\(\(rule_and_refint_t3)
+			 (\.id3a\s=\snew\.id3a\)\sAND\s\(rule_and_refint_t3)
+			 (\.id3b\s=\snew\.id3b\)\sAND\s\(rule_and_refint_t3)}
+		{$1 rule_and_refint_t3_1 $2_1$3_1$4_1}mx;
+
+		# Also fix old use of NATURAL JOIN syntax
+		$dump =~ s {NATURAL JOIN public\.credit_card r}
+			{JOIN public.credit_card r USING (cid)}mg;
+		$dump =~ s {NATURAL JOIN public\.credit_usage r}
+			{JOIN public.credit_usage r USING (cid)}mg;
+	}
+
+	# Suppress blank lines, as some places in pg_dump emit more or fewer.
+	$dump =~ s/\n\n+/\n/g;
+
+	return $dump;
+}
+
+# Internal subroutine to mangle whitespace within view/rule commands.
+# Any consecutive sequence of whitespace is reduced to one space.
+sub _mash_view_whitespace
+{
+	my ($dump) = @_;
+
+	foreach my $leader ('CREATE VIEW', 'CREATE RULE')
+	{
+		my @splitchunks = split $leader, $dump;
+
+		$dump = shift(@splitchunks);
+		foreach my $chunk (@splitchunks)
+		{
+			my @thischunks = split /;/, $chunk, 2;
+			my $stmt = shift(@thischunks);
+
+			# now $stmt is just the body of the CREATE VIEW/RULE
+			$stmt =~ s/\s+/ /sg;
+			# we also need to smash these forms for sub-selects and rules
+			$stmt =~ s/\( SELECT/(SELECT/g;
+			$stmt =~ s/\( INSERT/(INSERT/g;
+			$stmt =~ s/\( UPDATE/(UPDATE/g;
+			$stmt =~ s/\( DELETE/(DELETE/g;
+
+			$dump .= $leader . $stmt . ';' . $thischunks[0];
+		}
+	}
+	return $dump;
+}
+
+=pod
+
+=item adjust_new_dumpfile($old_version, $dump)
+
+Edit a dump output file, taken from the pg_upgrade'd installation
+by current-version C<pg_dumpall -s>, so that it will match the old
+dump output file as adjusted by C<adjust_old_dumpfile>.
+
+Typically this involves deleting data not present in the old installation.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from, represented as a
+PostgreSQL::Version object.
+
+=item C<dump>: Contents of dump file
+
+=back
+
+Returns the modified dump text.
+
+=cut
+
+sub adjust_new_dumpfile
+{
+	my ($old_version, $dump) = @_;
+
+	# use Unix newlines
+	$dump =~ s/\r\n/\n/g;
+
+	# Version comments will certainly not match.
+	$dump =~ s/^-- Dumped from database version.*\n//mg;
+
+	if ($old_version < 14)
+	{
+		# Suppress noise-word uses of IN in CREATE/ALTER PROCEDURE.
+		$dump =~ s/^(CREATE PROCEDURE .*?)\(IN /$1(/mg;
+		$dump =~ s/^(ALTER PROCEDURE .*?)\(IN /$1(/mg;
+		$dump =~ s/^(CREATE PROCEDURE .*?), IN /$1, /mg;
+		$dump =~ s/^(ALTER PROCEDURE .*?), IN /$1, /mg;
+		$dump =~ s/^(CREATE PROCEDURE .*?), IN /$1, /mg;
+		$dump =~ s/^(ALTER PROCEDURE .*?), IN /$1, /mg;
+
+		# Remove SUBSCRIPT clauses in CREATE TYPE.
+		$dump =~ s/^\s+SUBSCRIPT = raw_array_subscript_handler,\n//mg;
+
+		# Remove multirange_type_name clauses in CREATE TYPE AS RANGE.
+		$dump =~ s {,\n\s+multirange_type_name = .*?(,?)$} {$1}mg;
+
+		# Remove mentions of extended hash functions.
+		$dump =~
+		  s {^ALTER\sOPERATOR\sFAMILY\spublic\.part_test_int4_ops\sUSING\shash\sADD\n
+						\s+FUNCTION\s2\s\(integer,\sinteger\)\spublic\.part_hashint4_noop\(integer,bigint\);} {}mxg;
+		$dump =~
+		  s {^ALTER\sOPERATOR\sFAMILY\spublic\.part_test_text_ops\sUSING\shash\sADD\n
+						\s+FUNCTION\s2\s\(text,\stext\)\spublic\.part_hashtext_length\(text,bigint\);} {}mxg;
+	}
+
+	# pre-v12 dumps will not say anything about default_table_access_method.
+	if ($old_version < 12)
+	{
+		$dump =~ s/^SET default_table_access_method = heap;\n//mg;
+	}
+
+	# dumps from pre-9.6 dblink may include redundant ACL settings
+	if ($old_version lt '9.6')
+	{
+		my $comment =
+		  "-- Name: FUNCTION dblink_connect_u\(.*?\); Type: ACL; Schema: public; Owner: .*";
+		my $sql =
+		  "REVOKE ALL ON FUNCTION public\.dblink_connect_u\(.*?\) FROM PUBLIC;";
+		$dump =~ s/^--\n$comment\n--\n+$sql\n+//mg;
+	}
+
+	if ($old_version lt '9.3')
+	{
+		# CREATE VIEW/RULE statements were not pretty-printed before 9.3.
+		# To cope, reduce all whitespace sequences within them to one space.
+		# This must be done on both old and new dumps.
+		$dump = _mash_view_whitespace($dump);
+	}
+
+	# Suppress blank lines, as some places in pg_dump emit more or fewer.
+	$dump =~ s/\n\n+/\n/g;
+
+	return $dump;
+}
+
+=pod
+
+=back
+
+=cut
+
+1;
diff -pudr client-code-REL_16.orig/PGBuild/Modules/TestUpgradeXversion.pm client-code-REL_16/PGBuild/Modules/TestUpgradeXversion.pm
--- client-code-REL_16.orig/PGBuild/Modules/TestUpgradeXversion.pm	2023-01-13 12:20:51.000000000 -0500
+++ client-code-REL_16/PGBuild/Modules/TestUpgradeXversion.pm	2023-01-16 15:01:22.502366802 -0500
@@ -323,31 +323,6 @@ sub save_for_testing
 		return if $?;
 	}
 
-	if ($this_branch ne 'HEAD' && $this_branch le 'REL9_4_STABLE')
-	{
-		my $opsql = 'drop operator if exists public.=> (bigint, NONE)';
-
-		# syntax is illegal in 9.5 and later, and it shouldn't
-		# be possible for it to exist there anyway.
-		# quoting the operator can also fail,  so it's left unquoted.
-		run_psql("$installdir/bin/psql", "-e", $opsql, "regression",
-			"$upgrade_loc/fix.log", 1);
-		return if $?;
-	}
-
-	# remove dbs of modules known to cause pg_upgrade to fail
-	# anything not builtin and incompatible should clean up its own db
-	# e.g. jsonb_set_lax
-
-	foreach my $bad_module ("test_ddl_deparse")
-	{
-		my $dsql = "drop database if exists contrib_regression_$bad_module";
-
-		run_psql("$installdir/bin/psql", "-e", $dsql,
-			"postgres", "$upgrade_loc/fix.log", 1);
-		return if $?;
-	}
-
 	# use a different logfile here to get around windows sharing issue
 	system( qq{"$installdir/bin/pg_ctl" -D "$installdir/data-C" -w stop }
 		  . qq{>> "$upgrade_loc/ctl2.log" 2>&1});
@@ -375,6 +350,21 @@ sub test_upgrade    ## no critic (Subrou
 	print time_str(), "checking upgrade from $oversion to $this_branch ...\n"
 	  if $verbose;
 
+	# load helper module from source tree
+	unshift(@INC, "$self->{pgsql}/src/test/perl");
+	require PostgreSQL::Test::AdjustUpgrade;
+	PostgreSQL::Test::AdjustUpgrade->import;
+	shift(@INC);
+
+	# if $oversion isn't HEAD, convert it into a PostgreSQL::Version object
+	my $old_version = $oversion;
+	if ($old_version ne 'HEAD')
+	{
+		$old_version =~ s/REL_?(\d+(?:_\d+)?)_STABLE/$1/;
+		$old_version =~ s/_/./;
+		$old_version = PostgreSQL::Version->new($old_version);
+	}
+
 	rmtree "$other_branch/inst/$upgrade_test";
 	copydir(
 		"$other_branch/inst/data-C",
@@ -414,6 +404,7 @@ sub test_upgrade    ## no critic (Subrou
 
 	return if $?;
 
+	# collect names of databases present in old installation.
 	my $sql = 'select datname from pg_database';
 
 	run_psql("psql", "-A -t", $sql, "postgres",
@@ -425,186 +416,22 @@ sub test_upgrade    ## no critic (Subrou
 	do { s/\r$//; $dbnames{$_} = 1; }
 	  foreach @dbnames;
 
-	if ($this_branch gt 'REL9_6_STABLE' || $this_branch eq 'HEAD')
-	{
-		run_psql(
-			"$other_branch/inst/bin/psql",                         "-e",
-			"drop database if exists contrib_regression_tsearch2", "postgres",
-			"$upgrade_loc/$oversion-copy.log",                     1
-		);
-		return if $?;
-
-		run_psql(
-			"$other_branch/inst/bin/psql",
-			"-e",
-			"drop function if exists oldstyle_length(integer, text)",
-			"regression",
-			"$upgrade_loc/$oversion-copy.log",
-			1
-		);
-		return if $?;
-	}
-
-	# some regression functions gone from release 11 on
-	if (   ($this_branch ge 'REL_11_STABLE' || $this_branch eq 'HEAD')
-		&& ($oversion lt 'REL_11_STABLE' && $oversion ne 'HEAD'))
-	{
-		my $missing_funcs = q{drop function if exists public.boxarea(box);
-                              drop function if exists public.funny_dup17();
-                            };
-		$missing_funcs =~ s/\n//g;
-
-		run_psql("$other_branch/inst/bin/psql", "-e", $missing_funcs,
-			"regression", "$upgrade_loc/$oversion-copy.log", 1);
-		return if $?;
-	}
-
-	# avoid version number issues with test_ext7
-	if ($dbnames{contrib_regression_test_extensions})
-	{
-		my $noext7 = "drop extension if exists test_ext7";
-		run_psql(
-			"$other_branch/inst/bin/psql", "-e", $noext7,
-			"contrib_regression_test_extensions",
-			"$upgrade_loc/$oversion-copy.log", 1
-		);
-		return if $?;
-	}
-
-	# user table OIDS and abstime+friends are gone from release 12 on
-	if (   ($this_branch gt 'REL_11_STABLE' || $this_branch eq 'HEAD')
-		&& ($oversion le 'REL_11_STABLE' && $oversion ne 'HEAD'))
-	{
-		my $nooid_stmt = q{
-           DO $stmt$
-           DECLARE
-              rec text;
-           BEGIN
-              FOR rec in
-                 select oid::regclass::text
-                 from pg_class
-                 where relname !~ '^pg_'
-                    and relhasoids
-                    and relkind in ('r','m')
-                 order by 1
-              LOOP
-                 execute 'ALTER TABLE ' || rec || ' SET WITHOUT OIDS';
-                 RAISE NOTICE 'removing oids from table %', rec;
-              END LOOP;
-           END; $stmt$;
-        };
-		foreach my $oiddb ("regression", "contrib_regression_btree_gist")
-		{
-			next unless $dbnames{$oiddb};
-			run_psql("$other_branch/inst/bin/psql", "-e", $nooid_stmt,
-				"$oiddb", "$upgrade_loc/$oversion-copy.log", 1);
-			return if $?;
-		}
-
-		if (   $oversion ge 'REL_10_STABLE'
-			&& $dbnames{'contrib_regression_postgres_fdw'})
-		{
-			run_psql(
-				"$other_branch/inst/bin/psql",
-				"-e",
-				"drop foreign table if exists ft_pg_type",
-				"contrib_regression_postgres_fdw",
-				"$upgrade_loc/$oversion-copy.log",
-				1
-			);
-			return if $?;
-		}
-
-		if ($oversion lt 'REL9_3_STABLE')
-		{
-			run_psql(
-				"$other_branch/inst/bin/psql",
-				"-e",
-				"drop table if exists abstime_tbl, reltime_tbl, tinterval_tbl",
-				"regression",
-				"$upgrade_loc/$oversion-copy.log",
-				1
-			);
-			return if $?;
-		}
-	}
-
-	# stuff not supported from release 14
-	if (   ($this_branch gt 'REL_13_STABLE' || $this_branch eq 'HEAD')
-		&& ($oversion le 'REL_13_STABLE' && $oversion ne 'HEAD'))
+	if ($oversion ne $this_branch)
 	{
-		my $prstmt = join(';',
-			'drop operator if exists #@# (bigint,NONE)',
-			'drop operator if exists #%# (bigint,NONE)',
-			'drop operator if exists !=- (bigint,NONE)',
-			'drop operator if exists #@%# (bigint,NONE)');
-
-		run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-			"regression", "$upgrade_loc/$oversion-copy.log", 1);
-		return if $?;
-
-		$prstmt = "drop function if exists public.putenv(text)";
-
-		my $regrdb =
-		  $oversion le "REL9_4_STABLE"
-		  ? "contrib_regression"
-		  : "contrib_regression_dblink";
-
-		if ($dbnames{$regrdb})
-		{
-			run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-				"$regrdb", "$upgrade_loc/$oversion-copy.log", 1);
-			return if $?;
-		}
+		# obtain and execute commands needed to make old database upgradable.
+		my $adjust_cmds = adjust_database_contents($old_version, %dbnames);
 
-		if ($oversion le 'REL9_4_STABLE')
+		foreach my $updb (keys %$adjust_cmds)
 		{
-			# this is fixed in 9.5 and later
-			$prstmt = join(';',
-				'drop operator @#@ (NONE, bigint)',
-				'CREATE OPERATOR @#@ ('
-				  . 'PROCEDURE = factorial, '
-				  . 'RIGHTARG = bigint )');
-			run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-				"regression", "$upgrade_loc/$oversion-copy.log", 1);
-			return if $?;
-		}
+			my $upcmds = join(";\n", @{ $adjust_cmds->{$updb} });
 
-		if ($oversion le 'REL9_4_STABLE')
-		{
-			# this is fixed in 9.5 and later
-			$prstmt = join(';',
-				'drop aggregate if exists public.array_cat_accum(anyarray)',
-				'CREATE AGGREGATE array_larger_accum (anyarray) ' . ' ( '
-				  . '   sfunc = array_larger, '
-				  . '   stype = anyarray, '
-				  . '   initcond = $${}$$ '
-				  . '  ) ');
-			run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-				"regression", "$upgrade_loc/$oversion-copy.log", 1);
+			run_psql("$other_branch/inst/bin/psql", "-e -v ON_ERROR_STOP=1",
+				$upcmds, $updb, "$upgrade_loc/$oversion-fix.log", 1);
 			return if $?;
 		}
 	}
 
-	# stuff not supported from release 16
-	if (   ($this_branch gt 'REL_15_STABLE' || $this_branch eq 'HEAD')
-		&& ($oversion le 'REL_15_STABLE' && $oversion ne 'HEAD'))
-	{
-		# Can't upgrade aclitem in user tables from pre 16 to 16+.
-		# Also can't handle child tables with newly-generated columns.
-		my $prstmt = join(
-			';',
-			'alter table if exists public.tab_core_types
-						  drop column if exists aclitem',
-			'drop table if exists public.gtest_normal_child',
-			'drop table if exists public.gtest_normal_child2'
-		);
-
-		run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-			"regression", "$upgrade_loc/$oversion-copy.log", 1);
-		return if $?;
-	}
-
+	# perform a dump from the old database for comparison purposes.
 	my $extra_digits = "";
 
 	if (   $oversion ne 'HEAD'
@@ -793,65 +620,40 @@ sub test_upgrade    ## no critic (Subrou
 		return if $?;
 	}
 
-	foreach my $dump ("$upgrade_loc/origin-$oversion.sql",
-		"$upgrade_loc/converted-$oversion-to-$this_branch.sql")
-	{
-		# Change trigger definitions to say ... EXECUTE FUNCTION ...
+	# Slurp the pg_dump output files, and filter them if not same version.
+	my $olddumpfile = "$upgrade_loc/origin-$oversion.sql";
+	my $olddump     = file_contents($olddumpfile);
 
-		my $contents = file_contents($dump);
+	$olddump = adjust_old_dumpfile($old_version, $olddump)
+	  if ($oversion ne $this_branch);
 
-		# would like to use lookbehind here but perl complains
-		# so do it this way
-		$contents =~ s/
-                         (^CREATE\sTRIGGER\s.*?)
-                         \sEXECUTE\sPROCEDURE
-                      /$1 EXECUTE FUNCTION/mgx;
-		open(my $dh, '>', "$dump.fixed") || die "opening $dump.fixed";
-		print $dh $contents;
-		close($dh);
-	}
+	my $newdumpfile = "$upgrade_loc/converted-$oversion-to-$this_branch.sql";
+	my $newdump     = file_contents($newdumpfile);
 
-	system( qq{diff -I "^\$" -I "SET default_table_access_method = heap;" }
-		  . qq{ -I "^SET default_toast_compression = 'pglz';\$" -I "^-- " }
-		  . qq{-u "$upgrade_loc/origin-$oversion.sql.fixed" }
-		  . qq{"$upgrade_loc/converted-$oversion-to-$this_branch.sql.fixed" }
-		  . qq{> "$upgrade_loc/dumpdiff-$oversion" 2>&1});
+	$newdump = adjust_new_dumpfile($old_version, $newdump)
+	  if ($oversion ne $this_branch);
 
-	# diff exits with status 1 if files differ
-	return if $? >> 8 > 1;
+	# Always write out the filtered files, to aid in diagnosing filter bugs.
+	open(my $odh, '>', "$olddumpfile.fixed")
+	  || die "opening $olddumpfile.fixed: $!";
+	print $odh $olddump;
+	close($odh);
+	open(my $ndh, '>', "$newdumpfile.fixed")
+	  || die "opening $newdumpfile.fixed: $!";
+	print $ndh $newdump;
+	close($ndh);
 
-	open(my $diffile, '<', "$upgrade_loc/dumpdiff-$oversion")
-	  || die "opening $upgrade_loc/dumpdiff-$oversion: $!";
-	my $difflines = 0;
-	while (<$diffile>)
+	# Are the results the same?
+	if ($olddump ne $newdump)
 	{
-		$difflines++ if /^[+-]/;
-	}
-	close($diffile);
-
-	# If the versions match we require that there be no diff lines.
-	# In the past we have seen a handful of diffs from reordering of
-	# large object output, but that appears to have disppeared.
-	# If the versions don't match we heuristically allow more lines of diffs
-	# based on observed differences. For versions from 9.6 on, that's
-	# not very many lines, though.
+		# Trouble, so run diff to show the problem.
+		system( qq{diff -u "$olddumpfile.fixed" "$newdumpfile.fixed" }
+			  . qq{> "$upgrade_loc/dumpdiff-$oversion" 2>&1});
 
-	if (
-		($oversion eq $this_branch && $difflines == 0)
-		|| (   $oversion ne $this_branch
-			&& $oversion ge 'REL9_6_STABLE'
-			&& $difflines < 90)
-		|| (   $oversion ne $this_branch
-			&& $oversion lt 'REL9_6_STABLE'
-			&& $difflines < 700)
-	  )
-	{
-		return 1;
-	}
-	else
-	{
 		return;
 	}
+
+	return 1;
 }
 
 sub installcheck

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