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.
+
+    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.)
 
 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.
+    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 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.
+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/bin/pg_upgrade/upgrade_adapt.sql b/src/bin/pg_upgrade/upgrade_adapt.sql
deleted file mode 100644
index a368a51ff5..0000000000
--- a/src/bin/pg_upgrade/upgrade_adapt.sql
+++ /dev/null
@@ -1,115 +0,0 @@
---
--- SQL queries for upgrade tests across different major versions.
---
--- This file includes a set of SQL queries to make a cluster to-be-upgraded
--- compatible with the version this file is based on.  Note that this
--- requires psql, as per-version queries are controlled with a set of \if
--- clauses.
-
--- This script is backward-compatible, so it is able to work with any version
--- newer than 9.2 we are upgrading from, up to the branch this script is stored
--- on (even if this would not run if running pg_upgrade with the same version
--- for the origin and the target).
-
--- \if accepts a simple boolean value, so all the version checks are
--- saved based on this assumption.
-SELECT
-  ver <= 902 AS oldpgversion_le92,
-  ver <= 904 AS oldpgversion_le94,
-  ver <= 906 AS oldpgversion_le96,
-  ver <= 1000 AS oldpgversion_le10,
-  ver <= 1100 AS oldpgversion_le11,
-  ver <= 1300 AS oldpgversion_le13,
-  ver <= 1500 AS oldpgversion_le15
-  FROM (SELECT current_setting('server_version_num')::int / 100 AS ver) AS v;
-\gset
-
--- Objects last appearing in 9.2.
-\if :oldpgversion_le92
--- Note that those tables are removed from the regression tests in 9.3
--- and newer versions.
-DROP TABLE abstime_tbl;
-DROP TABLE reltime_tbl;
-DROP TABLE tinterval_tbl;
-\endif
-
--- Objects last appearing in 9.4.
-\if :oldpgversion_le94
--- This aggregate has been fixed in 9.5 and later versions, so drop
--- and re-create it.
-DROP AGGREGATE array_cat_accum(anyarray);
-CREATE AGGREGATE array_larger_accum (anyarray) (
-                  sfunc = array_larger,
-                  stype = anyarray,
-                  initcond = $${}$$);
--- This operator has been fixed in 9.5 and later versions, so drop and
--- re-create it.
-DROP OPERATOR @#@ (NONE, bigint);
-CREATE OPERATOR @#@ (PROCEDURE = factorial,
-                     RIGHTARG = bigint);
-\endif
-
--- Objects last appearing in 9.6.
-\if :oldpgversion_le96
-DROP FUNCTION public.oldstyle_length(integer, text);
-\endif
-
--- Objects last appearing in 10.
-\if :oldpgversion_le10
-DROP FUNCTION IF EXISTS boxarea(box);
-DROP FUNCTION IF EXISTS funny_dup17();
-\endif
-
--- Objects last appearing in 11.
-\if :oldpgversion_le11
--- WITH OIDS is supported until v11, so remove its support for any
--- relations marked as such.
-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', 'f')
-    ORDER BY 1
-  LOOP
-    EXECUTE 'ALTER TABLE ' || quote_ident(rec) || ' SET WITHOUT OIDS';
-  END LOOP;
-  END; $stmt$;
-\endif
-
--- Objects last appearing in 13.
-\if :oldpgversion_le13
--- Until v10, operators could only be dropped one at a time, so be careful
--- to stick with one command for each drop here.
-DROP OPERATOR public.#@# (pg_catalog.int8, NONE);
-DROP OPERATOR public.#%# (pg_catalog.int8, NONE);
-DROP OPERATOR public.!=- (pg_catalog.int8, NONE);
-DROP OPERATOR public.#@%# (pg_catalog.int8, NONE);
-\endif
-
--- Objects last appearing in 15.
--- The internal format of "aclitem" has changed in 16, so replace it with
--- text type in tables.
-\if :oldpgversion_le15
-DO $stmt$
-  DECLARE
-    rec record;
-  BEGIN
-  FOR rec in
-    SELECT oid::regclass::text as rel, attname as col
-    FROM pg_class c, pg_attribute a
-    WHERE c.relname !~ '^pg_'
-      AND c.relkind IN ('r')
-      AND a.attrelid = c.oid
-      AND a.atttypid = 'aclitem'::regtype
-    ORDER BY 1
-  LOOP
-    EXECUTE 'ALTER TABLE ' || quote_ident(rec.rel) || ' ALTER COLUMN ' ||
-      quote_ident(rec.col) || ' SET DATA TYPE text';
-  END LOOP;
-  END; $stmt$;
-\endif
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;